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Statement:

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This material is for personal use only, and can not be used by any individual or organization for any commercial purposes.

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HUAWEI TECHNOLOGIES CO., LTD.

Huawei Confidential

1

Basic Optical Communications Technology

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Content :

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1. Preparatory Knowledge························································································4

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2. Optical Fiber ·········································································································8 3. Passive components·····························································································26

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Confidential Information of Huawei. No Spreading Without Permission

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Light rays propagate within different media at a different velocities. The characteristics that describes property of a media is called refractive index.

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Refractive index n is determined by the following formula: n=с/ν.

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In figure1: θ1 is the angle of incidence, θ3 is the angle of reflection, and θ2 is the angle of refraction. The relationship among these angles depends on the medium the light rays strikes: θ1=θ3, n1 sinθ1=n2 sinθ2.

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In figure2: When the angle of incidence θ reaches a value, the refraction angle equals 90°, the light will not enter another medium (air in this example), and the angle of incidence then is called the critical angle θc. If we continue to increase the angle of incidence θ to make θ＞θc, all light will be reflected back into the incident medium. This phenomenon is called total reflection because all light is reflected back to the medium of

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Light is a kind of transverse wave, that is, the direction of vibration of the electromagnetic field of light is vertical to the direction of propagation. If the direction of vibration of light wave remains constant, and the amplitude of the light wave varies with phase, such light is called linearly polarized light.

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In the propagation course of natural light, light intensity varies with the direction of vibration due to external influence, and light intensity at a direction prevails over that at other directions. Such light is called partially polarized light.

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The material of the prism (glass) or water has different indices of refraction (n) for light of different wavelengths (corresponding to different colors). As a result, the propagation velocity and the refractive angle of the light differ and lights of different colors spread across the space.

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Fiber is of cylindrical form and consists of the core, cladding and coating.

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Core is lying at the center of the fiber, it is made from high purity silicon dioxide, mixing with a small amount of doping agent to increase the refractive index (n1) of core.

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Cladding is around the core and is also made from high purity silicon dioxide mixing with a trivial amount of doping agent. The doping agent here is to reduce the refractive index (n2) of the cladding and make it slightly lower than that of the core.

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Step index fiber: the refractive indices of the core and cladding are evenly distributed along the radius of the fiber, and the refractive rate changes abruptly at the interface between the core and the cladding.

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Graded index fiber: the refractive index of the core is not constant, but reduces gradually with the increase of the coordinate along the radius of core to the extent that it ultimately

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Light is propagated in the fiber as an independent group of light ray. In other words, we will find out, if we could look into the fiber, that a group of light beam propagates at different angles ranging from zero to critical angle αc. The light with an angle larger than αc will pass through the core into the cladding. These different light beams are modes.

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The mode of propagation strictly following the central axis of the fiber is called zero-order mode, or fundamental mode; other beams which propagate along an angle from the central axis are called high-order modes.

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When the size of the fiber (mainly the diameter of core d1) is far larger than the optical wavelength (about 1 micrometer), there will be tens of or even hundreds of transmission modes in fiber. Such fiber is called multimode fiber.

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When the size of the fiber (mainly the diameter of core d1) is comparatively small and at the same order of magnitude as the optical wavelength (e.g. d1 is within the range of 5 to 10 micrometers), the fiber allows only one propagation mode (fundamental mode) and cuts off other high-order modes. Such fiber is called single-mode fiber.

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Attenuation or loss is an important constraint factor of fiber for the propagation of optical signal. Loss of fiber restricts the propagation distance of optical signal without optical amplification. Loss of fiber mainly depends on absorption loss, scattering loss and bending loss.

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Absorption loss of fiber results from the material of fiber, which includes ultraviolet absorption, infrared absorption and impurity absorption.

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Scattering loss resulting from the inhomogeneity of materials is called Rayleigh scattering loss.

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Bending of fiber tends to cause radiation loss.

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Loss is one of major characteristics of fiber and the major parameter used to describe such loss is attenuation coefficient.

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Different frequencies and modes in the optical pulse have different group velocities. Therefore, these frequency components and modes reach the fiber terminals at different time, and result in optical pulse stretching, which is the dispersion of fiber.

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Light beams of different modes in multimode fiber have different group velocities and they have different time delays in transmission, dispersion arising from which is called mode dispersion. Mode dispersion is mainly associated with multimode fiber.

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Chromatic dispersion is the sum of material dispersion and waveguide dispersion. All two depend on wavelength. Chromatic dispersion is the different light speed in fiber according to the light wavelength. In vacuum, the light propagate at the same speed, in a certain medium, such as quartz crystal silicon dioxide, however, different wavelength has different propagation speed. This diagram is the dispersion curve of the different SMF.

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Light can be polarized in vertical and horizontal. Because of geometric imperfection of the fiber. PMD is caused by slight fiber asymmetry. Different Polarization travel at different speed. PMD is statistical in nature. Large variation in PMD values can be observed during the life cycle of a fiber. Additional stress can be applied to a fiber during transportation and cabling. Effects of temperature and vibration are still regarded as potential problem by operator. Cable can be crushed, stressed, or physically damaged during installation. Cable handling causes variations in PMD.

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Optical pulse from LD is not monochromatic, it is composed of many wavelengths or colors. The chromatic dispersion in the fiber causes different wavelength to travel at different speed, cause different of propagation delay, and, at the receiver, arrive at the different time.

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The adjacent optical pulse overlap. It causes inter-symbol interference and bit error.

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When actual wavelength is smaller than cutoff wavelength, there will be several modes transmitted in the SMF, thus assuming multimode characteristics. To avoid mode noise and mode dispersion, the cutoff wavelength of the minimum fiber length of actual system fiber should be smaller than the minimum operating wavelength of the system. Cutoff wavelength conditions can ensure single-mode transmission in minimum fiber length, inhibit the generation of high-order modes, or reduce the cost of generated high-order mode noise power to such an extent that it can be neglected.

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In fiber, not all luminous energy is transmitted via core, but some luminous energy is transmitted via cladding. MFD is the parameter used to describe the concentration of luminous energy in SMF.

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MFD and effective area mainly relate to the density of energy passing through the fiber. The smaller the MFD, the greater the energy density passing through the cross section of the fiber. Excessively large energy density of the fiber will lead to the non-linear effects, lower the optical SNR, and greatly affect the system performance. Therefore, as for the MFD (or effective area) of the transmission fiber, the larger the better.

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G.652 fiber is one of the single-mode optical fiber defined by recommendation G.652. this fiber also be called conventional SMF. G.652 fiber has the zero-dispersion wavelength around 1310nm and it is optimized for use in the 1310nm wavelength region. G.652 fiber can also be used in 1550nm wavelength region.

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G.653 fiber, also known as dispersion shifted fiber (DSF), refers to the fiber whose zero point of dispersion is close to 1,550nm. It is called so because its zero point of dispersion has shifted compared with standard SMF (G.652).

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G.654 fiber refers to the SMF with shifted cutoff wavelength. It’s is mainly applicable to submarine fiber communications where long regenerator section distance is required.

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G.655: DWDM system working at zero dispersion wavelength is easily subject to four-wave mixing effect (as described in the following section), which seriously affects the system

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performance. To avoid such effect, the zero point of dispersion will be shifted out of the operating wavelength of DWDM close to 1550nm. This kind of fiber is non-zero dispersion shifted fiber (NZDSF).


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All media are non-linear in nature. However, on most occasions, the non-linear characteristics are rather negligible to be perceived. However, the non-linear characteristics of the fiber will become stronger and stronger when an optical amplifier or laser is employed in the fiber communication system. The reason is that the optical signal of SMF is confined to the mode field and the effective area of SMF is rather small. As a result, optical power density is very high and such high power density will remain over a long distance due to low loss.

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Non-linear effects of SMF is usually divided into: stimulated non-elastic scattering, Kerr effect and four-wave mixing.

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Assume that the frequency of incident light is ω1, and the molecular vibration frequency of the medium is ωv, then the frequency of scattered light ωs=ω1-ωv and ωas=ω1+ωv. This phenomenon is called stimulated Raman scattering.

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Stimulated Brillouin scattering is very similar to stimulated Raman scattering in the physical process. The pump with the incident frequency of ωp transfers part of the energy to the Stokes wave with the frequency of ωs, and emits phonons with the frequency of Ω.

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We call the phenomenon that the refractive index of a medium changes with the variation of light intensity “Kerr effect”. In a single-mode fiber, Kerr effect appears as self-phase modulation and cross phase modulation.

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Due to Kerr effect, an instant change of signal light intensity tends to lead to the phase change of optical pulse. This effect is called self-phase modulation (SPM).

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In a multi-channel system, when changes of the light intensity cause phase changes, the phase modulation will generally broaden the signal spectrum as a result of interaction between adjacent channels. The extent of spectrum broadening caused by XPM is related to the channel spacing.

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The frequency of the new wavelength is the combination of the tree, as shown in the following formula: flnm=fl±fn±fm.

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occurrence of FWM requires phase match of signal lights. When various signal lights are transmitted near zero dispersion of the fiber, the group velocities of optical signals with different wavelengths are nearly the same. Therefore, the phase match condition is quite easy to satisfy, and thus FWM effect is likely to occur.

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FWM effect is much more serious on a G.653 fiber than on G.652 and G.655 fibers, and the transmission loss caused thereby is bigger. Appropriate dispersion can suppress the occurrence of FWM.

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A dielectric thin film filter is composed of several dozens of layers of dielectric films with different materials, different refractive indices and different thickness.

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film interfering filter can provide a pass band to a certain range of wavelengths, and provide a block band to other wavelengths, so as to form the filter characteristics as required.

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The main characteristics of the dielectric thin film filter are: a miniaturized device with stable structure, flattened and polarization independent signal pass band, low insertion loss, reasonable path interval and stable temperature which is better than 0.0005nm/°C.

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Fiber grating is formed by means of manual introduction of a periodic refractive index variation along the length of a section of fiber. Fiber grating is a space phase fiber grating formed in the core by means of the optical sensitivity of the fiber material (the permanent change of refractive index caused by the interaction between the external incident photons with the core).

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According to the distribution mode of the refractive index on the fiber axial direction, the fiber grating can be divided into uniform grating and non-uniform grating. Uniform grating refers to the grating with constant optical cycle (the product of the effective refractive index and the refractive index modulation depth) along the fiber axial direction, such as Bragg grating and long-cycle grating. Non-uniform grating refers to the grating with optical cycle varies along the fiber axial direction, such as chirped grating

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Arrayed waveguide grating (AWG) is a plane waveguide device on the basis of optical integration technology. The typical manufacturing process is to d brought into the lab for eposite a layer of thin silica glass on a piece of silica, and then form the pattern and shape by means of the optical scoring technology.

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The AWG optical multiplexer/demultiplexer features small wavelength interval, large number of channels and flattened passband etc., making it very suitable for the superhighspeed and large-capacity DWDM system.

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The basic working principle of this device is shown in the figure above. Input light with an interval of 50G can be divided into odd and even groups by means of an interleaver with an interval of 50G, with the interval of each group being 100G; and then the input light is divided into four groups with an interval of 200G by means of two interleavers with an interval of 100G; finally, the input light is demultiplexed by means of a common demultiplexer with an interval of 200G. Of course, at the second stage, the input light can be demultiplexed into a single-wavelength optical signal directly by means of an AWG or a thin film filter with an interval of 100G.

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By means of this device, the toll trunk can be conveniently upgraded to the DWDM system with an interval of 50G, without wasting the existing multiplexer and demultiplexer with an interval of 100G, thus it is cost efficient.

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Optical coupler is a device for combining the lights from different fibers; and optical splitter, just as it name implies, is a device for splitting the optical signals to several fibers.

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In fiber-optic communication links, light is reflected from any components -connector, passive device and receiver and so on – inserted into the optical path. If the backreflection light enters a laser or optical amplifier, the performance of this device will degrade. Isolator is to isolate the laser or optical amplifier from the reflected light. The isolator must allow the forward light pass through with minimal loss (ideally, 0), and block backreflection light with maximum loss (ideally, infinity). Insertion loss of a modern isolator can be as low as 0.15dB, while isolation can be as high as 70dB.

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Circulator is a kind of one way device. It direct a light signals from one port to another sequentially in only one direction. The light inputted from port1 can be only outputted from port2 (isolation between port1 and port2); the light inputted from port2 can be only outputted from port3; and the light inputted from port3 can be only outputted from port1

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It is the basic device for optical communication, the optical switches have many applications. These applications mainly include:

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Automatic protection switch: In the case of fiber broken or sending device failure, the optical switch can be used to realize the protective switchover. The signals are switched to the standby protection fiber or transmitter through the optical switch. This is the most basic application of the optical switch, which is generally realized by a 12 or 1N switch.

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Dynamic Optical Add/Drop Multiplexer (OADM): The dynamic OADM can add/drop one wavelength from multiple wavelengths without OEO conversion. In the future, the dynamic OADM will be applied to both long-haul system and MAN, especially applied to the MAN to construct ring network. Optical switch is not mandatory for OADM. However, the OADM with optical switch can be switched to optical channel flexibly, and provides

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dynamic upload and download functions, that means, the selected wavelengths to be downloaded can be done through software intervention. To meet the network requirements, OADM can be connected with 22 optical switch or 1616 optical switch (for MAN) or 6464 (for toll trunk).

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Optical cross connection (OXC): It represents a new core technology in the network. OXC means the high density network and any end-to-end optical cross connection. It can

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Answer: 1)

Dielectric Thin Film Filter

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Fiber Grating

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Arrayed Waveguide Grating-AWG

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Comb Filter

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Optical Coupler and Optical Splitter

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6) 7)

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Isolator and Circulator Optical Switch

For their functions, please refer to the above contents.

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SDH Principle

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Contents

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SDH Overview……………………………...……………………………..…..……..Page3

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Frame Structure & Multiplexing Methods…………………………….……..……Page11 Overheads & Points……………………………………………………......………Page26

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SDH Principle

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SDH Principle

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SDH Principle

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SDH is the abbreviation of Synchronous Digital Hierarchy.

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SDH is a transmission system (protocol) which defines the characteristic of digital signals, including frame structure, multiplexing method, digital rates hierarchy, and interface code pattern, and so on.

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SDH Principle

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No universal standards for optical interfaces. All PDH equipment manufacturers use their own line codes to monitor the transmission performance in the optical links. So equipment at the two ends of a transmission link must be provided by the same vendor. This causes many difficulties for network structuring, management and network interconnection.

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SDH electrical interfaces 

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There are only some regional standards: European Series, North American Series and Japanese Series, instead of universal standards for electrical interface. Each of them has different electrical interface rate levels, frame structures and multiplexing methods. This makes it difficult for international interconnection.

PDH optical interfaces 

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PDH (Plesiochronous Digital Hierarchy) electrical interfaces 

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SDH system provides universal standards for network node interfaces (NNI), including standards on digital signal rate level, frame structure, multiplexing method, line interface, etc. So SDH equipment of different vendors can be easily interconnected.

SDH optical interfaces 

Line interfaces (here refers to optical interface) adopt universal standards. Line coding of SDH signals is only universal scrambling. Therefore the opposite-terminal equipment can be interconnected with SDH equipment of different vendors via standard descrambler alone.


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SDH Principle

P-6

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As PDH system adopts asynchronous multiplexing method, the locations of the low-rate signals are not regular nor fixed when they are multiplexed into higher-rate signals. That is to say, the locations of the lower signals are unable to be identified from the higher speed

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signals. Therefore, low-rate signals can not be directly added/dropped from PDH high-rate signals. For example, 2Mb/s signals can not be directly added/dropped from 140Mb/s signals. Here arise two problems: 

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Adding/dropping low-rate signals from high-rate signals must be conducted level by level. This not only enlarges the size and increases cost, power consumption and complexity of equipment, but also decreases the reliability of the equipment.



Since adding/dropping low-rate signals to high-rate ones must go through many stages of multiplexing and de-multiplexing, impairment to the signals during

multiplexing/de-multiplexing processes will increase and transmission performance will deteriorate. This is unbearable in large capacity transmission. That's the reason why the transmission rate of PDH system has not being improved further.

No universal network management interface in PDH system 

Different parts of the network may use different network management systems, which are obstacles in forming an integrated telecommunication management system (TMN).


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SDH Principle

P-7

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As low-rate SDH signals are multiplexed into the frame structure of high-rate SDH signals via byte interleaved multiplexing method, their locations in the frame of high-rate SDH signal are fixed and regular, or say, predictable. Therefore, low-rate SDH signals, e.g.

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155Mb/s, (Synchronous Transport Module STM-1 ), can be directly added to or dropped from high-rate signals, e.g., 2.5Gb/s (STM-16 ). This simplifies the multiplexing and demultiplexing processes of signals and makes SDH hierarchy especially suitable for high rate and large capacity optical fiber transmission systems. 

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As synchronous multiplexing method and flexible mapping structure are employed, PDH low-rate tributary signals (e.g., 2Mb/s ) can also be multiplexed into SDH signal frame (STM-N). Their locations in STM-N frame are also predictable. So low-rate tributary signals can be directly added to or dropped from STM-N signals. Note that this is different from

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the above process of directly adding/dropping low-rate SDH signals to/from high-rate SDH signals. Here it refers to direct adding/dropping of low-rate tributary signals, such as 2Mb/s, 34Mb/s, and 140Mb/s, to/from SDH signals. This saves lots of multiplexing/de-multiplexing equipment (back-to-back equipment), enhances reliability, and reduces signal impairment, and the cost, power consumption and complexity of the equipment. Adding/dropping of services is further simplified.


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SDH Principle

P-8

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PDH OAM function 

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In the frame structure of PDH signals, there are few overhead bytes used for operation, administration and maintenance (OAM). The fact that few overhead

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bytes are used for the OAM of PDH signals is also a disadvantage for layered management, performance monitoring, real-time service dispatching, bandwidth control, and alarm analyzing and locating of the transmission network. 

SDH OAM function 

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Abundant overhead bits for operation, administration and maintenance (OAM) functions are arranged in the frame structures of SDH signals. This greatly enforces the network monitoring function, i.e. automatic maintenance. Some redundancy bits must be added during line coding for line performance monitoring because

few overhead bytes are arranged in PDH signals. For example, in the frame structure of PCM30/32 signals, only the bits in TS0 and TS16 time slots are used for OAM function.

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The abundant overheads in SDH signals account for 1/20 of the total bytes in a frame. It greatly enhances the OAM function and reduces the cost of system maintenance that occupies most of the overall cost of telecommunication equipments. The overall cost of SDH system is less than that of PDH system and estimated to be only 65.8% of that of the later.


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SDH Principle

P-9

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SDH has high compatibility, which means that the SDH transmission network and the existing PDH transmission network can work together while establishing SDH transmission network. SDH network can be used for transmitting PDH services, as well as signals of

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other hierarchies, such as asynchronous transfer mode (ATM) signals and FDDI signals. 

How does the SDH transmission network achieve such compatibility? The basic transport module (STM-1) of SDH signals in SDH network can accommodate three PDH digital signal hierarchies and other hierarchies such as ATM, FDDI and DQDB. This reflects the forward and backward compatibility of SDH and guarantees smooth transitions from PDH to SDH network and from SDH to ATM.

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How does SDH accommodate signals of these hierarchies? It simply multiplexes the lowrate signals of different hierarchies into the frame structure of the STM-1 signals at the

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boundary of the network (e.g. SDH/PDH start point) and then de-multiplexes them at the boundary of the network (end point). In this way, digital signals of different hierarchies can be transmitted in the SDH transmission network.

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SDH Principle

P-10

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Low bandwidth utilization ratio 

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One significant advantage of SDH is that system reliability is greatly enhanced (highly automatic OAM) since many overhead bytes for OAM function are

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employed in SDH signals. To transmit the same amount of valid information, PDH signals occupy less frequency bandwidth (transmission rate) than SDH signals, i.e. PDH signals use lower rate. In other words, STM-1 occupies a frequency bandwidth larger than that needed by PDH E4 signals (they have the same amount of information). 

Complex mechanism of pointer justification

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The pointer constantly indicates the location of low-rate signals so that specific low-rate signals can be properly de-multiplexed in time of "unpacking". However,

the pointer function increases the complexity of the system. Most of all, it generates a kind of special jitter in SDH system ---- a combined jitter caused by pointer justification. This jitter will deteriorate the performance of low-rate signals being de-multiplexed.

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Influence of excessive use of software on system security 

One of the features of SDH is its highly automatic OAM, which means that software constitutes a large proportion in the system. As a result, SDH system is vulnerable to computer viruses, manual mis-operation and software fault on network layer.


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SDH Principle

P-11

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SDH Principle

P-12

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ITU-T defines the frames of STM-N as rectangle block frame structure in unit of byte (8bit).

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The frame structure of STM-N signals is 9 rows× 270×N columns. The N here is equal to the N in STM-N, ranging from 1, 4, 16, 64, and 256. The N indicates that this signal is

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multiplexed by N STM-1 signals via byte interleaved multiplexing. This explains that the frame structure of STM-1 signals is a block structure of 9 rows ×270 columns. When N STM-1 signals are multiplexed into STM-N signal via byte interleaved multiplexing, only the columns of STM-1 signals are multiplexed via byte interleaved multiplexing. While the number of rows remains constantly to be 9. It is known that signals are transmitted bit-bybit in lines. Then what is the sequence of transmission? The principle for SDH signal frame transmission is: the bytes (8-bit) within the frame structure is transmitted bit-by-bit from left to right and from top to bottom. After one row is transmitted, the next row will follow.

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After one frame is completed, the next frame will start. ITU-T defines the frequency to be 8000 frames per second for all levels in STM hierarchy. That means the frame length or frame period is a constant value of 125us. Constant frame period is a major characteristic of SDH signals. The constant frame period makes the rates of STM-N signals regular. For example, the data rate of STM-4 transmission is constantly 4 times as that of STM-1, and STM-16 is 4 times of STM-4 and 16 times of STM-1. Such regularity of SDH signals makes it possible to directly add/drop low-rate SDH signals to/from high-rate SDH signals, especially for high-capacity transmission.


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SDH Principle

P-13

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The frame of STM-N consists of three parts 

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Section Overhead (including Regenerator Section Overhead --- RSOH and Multiplex Section Overhead ---- MSOH)

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Administrative Unit Pointer---- AU-PTR

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Information Payload

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SDH Principle

P-14

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The Information Payload is a place in the STM-N frame structure to store various information code blocks to be transmitted by STM-N. It functions as the "wagon box" of the truck---STM-N. Within the box are packed low-rate signals ---- cargoes to be shipped.

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To monitor the possible impairment to the cargoes (the packed low-rate signals) on a realtime basis during transmission, supervisory overhead bytes ---- Path Overhead (POH) bytes are added into the signals when the low-rate signals are packed. As one part of payload, the POH, together with the information code blocks, is loaded onto STM-N and transmitted on the SDH network. The POH is in charge of monitoring, administrating and controlling (somewhat similar to a sensor) the path performances for the packed cargoes (the low-rate signals).

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What is a path? Let's take the following example. STM-1 signals can be demultiplexed into

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63× 2Mb/s signals. In other words, STM-1 can be regarded as a transmission path divided into 63 bypaths. Each bypath, which is equal to a low-rate signal path, transmits corresponding low-rate signals. The function of the Path Overhead is to monitor the transmission condition of these bypaths. The 63 2Mb/s paths multiplex and form the path of STM-1 signals that can be regarded as a "section" here. Paths refer to corresponding low-rate tributary signals. The function of POH is to monitor the performance of these lowrate signals transmitted via the STM-N on the SDH network. This is consistent with the analogy in which the STM-N signal is regarded as a truck and the low-rate signals are packed and loaded onto the truck for transmission.

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SDH Principle

P-15

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The Section Overhead (SOH) refers to the auxiliary bytes which is necessary for network operation, administration and maintenance (OAM) to guarantee normal and flexible transmission of Information Payload. For example, the Section Overhead can monitor the

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impairment condition of all "cargoes" in STM-N during transmission. The function of POH is to locate the certain impaired cargo in case impairments occurred. SOH implements the overall monitoring of cargoes while the POH monitors a specific cargo. 

The Section Overhead is further classified into Regenerator Section Overhead (RSOH) and Multiplex Section Overhead (MSOH). They respectively monitor their corresponding sections and layers. Then, what's the difference between RSOH and MSOH? In fact, they have different monitoring domains. For example, if STM-16 signals are transmitted in the fiber, the RSOH monitors the overall transmission performance of STM-16 while the MSOH

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monitors the performances of each STM-1 of the STM-16 signals. RSOH, MSOH and POH provide SDH signals with monitoring functions for different layers. For a STM-16 system, the RSOH monitors the overall transmission performance of the STM-16 signal; the MSOH monitors the transmission performances of each STM-1 signal; and the POH monitors the transmission performances of each packaged low-rate tributary signal (e.g. 2Mb/s) in STM-1. Through these complete monitoring and management functions for all levels, you can conveniently conduct macro (overall) and micro (individual) supervision over the transmission status of the signal and easily locate and analyze faults.


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SDH Principle

P-16

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The Administrative Unit Pointer within column 9 × N of row 4 of the STM-N frame is 9 × N bytes in total. What's the function of AU-PTR? We have mentioned before those lowrate tributaries (e.g. 2Mb/s) could be added/dropped directly from high-rate SDH signals.

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Because the locations of low-rate signals within a high-rate SDH frame structure are predictable, i.e. regular. The predictability can be achieved via the pointer overhead bytes function in the SDH frame structure. The AU-PTR indicates the exact location of the first byte of the information payload within the STM-N frame so that the information payload can be properly extracted at the receiving end according to the value of this location indicator (the value of the pointer). Let's make it easier. Suppose that there are many goods stored in a warehouse in unit of pile. Goods (low-rate signals) of each pile are regularly arranged (via byte interleaved multiplexing). We can locate a piece of goods within the warehouse by only locating the pile this piece of goods belongs to. That is to say, as long as the location of the first piece of goods is known, the precise location of any piece within the pile can be directly located according to the regularity of their arrangement. In this way you can directly carry (directly add/drop) a given piece of goods (low-rate tributary) from the warehouse. The function of AU-PTR is to indicate the location of the first piece of goods within a given pile.

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In fact, the pointer is further classified into higher order pointer and low order pointer. The higher order pointer is AU-PTR while the lower order pointer is TU-PTR (Tributary Unit Pointer). The function of TU-PTR is similar to that of AU-PTR except that the former indicates smaller "piles of goods".


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SDH Principle

P-17

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SDH multiplexing includes three types: multiplexing of lower-order SDH signals into higherorder SDH signals and multiplexing of low-rate tributary signals (e.g. 2Mb/s, 34Mb/s and 140Mb/s) into SDH signals ----STM-N, and other hierarchy signals to SDH Signals. 

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The second type of multiplexing from Low to high rate SDH signals is conducted mainly via byte interleaved by multiplexing four into one, e.g. 4×STM-1-->STM-4 and 4×STM-4-->STM-16. after the multiplexing, the rate of the higher-level STM-N signals is 4 times that of the next lower-level STM-N signals. During the byte interleaved multiplexing, the information payload, pointer bytes of each frame are multiplexed via interleaved multiplexing based on their original values.

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The second type of multiplexing is mostly used for multiplexing of PDH signals into the STM-N signals.

The last one is other hierarchy signals e.g. IP or ATM signals to SDH Signals.

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SDH Principle

P-18

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ITU-T defined a complete multiplexing structure, through which digital signals of three PDH hierarchies can be multiplexed into STM-N signals. 

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This multiplexing structure includes some basic multiplexing units: C - Container, VC - Virtual Container, TU - Tributary Unit, TUG - Tributary Unit Group, AU Administrative Unit, and AUG - Administrative Unit Group. The suffixes of these multiplexing units denote their corresponding signal levels.

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Low-rate tributaries are multiplexed into STM-N signals through three procedures: mapping, aligning and multiplexing.

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The multiplexing route used in a country or an area must be unique. The route on the slide is the most usual and adopted in most of countries.



SDH mapping is a procedure by which tributaries are adapted into virtual

containers at the boundary of an SDH network, e.g. E1 into VC-12. 



SDH aligning is a procedure to add TU-PTR or AU-PTR into the VC-12, VC-3 or VC4. The pointer value constantly locates the start point of VC within the TU or AU. So that the receiving end can correctly separate the corresponding VC. SDH multiplexing, a relatively simple concept, is the procedure by which the TUs are organized into the higher order VC or the AUs are organized into STM-N via byte interleaving.


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SDH Principle

P-19

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First, the 140Mb/s PDH signals are adapted via bit rate justification (bit stuffing method) into C-4, which is a standard information structure used to accommodate 140Mb/s PDH signals. After being processed via bit rate justification techniques, service signals of various rates involved in SDH multiplexing must be loaded into a standard container corresponding to the rate level of the signal: 2Mb/s---C-12, 34Mb/s---C-3 and 140Mb/s---C-4. The main function of a container is for bit rate justification. The frame structure of C-4 is block frame in unit of bytes, with the frame frequency of 8000-frame per second.

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From C4 to VC4

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From 140Mb/s to C4

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A column of path overhead bytes (higher-order path overhead VC-4-POH) shall be added in front of the C-4 block frame during multiplexing in order to monitor the 140Mb/s path signals. Then the signals become a VC-4 information structure. The virtual container, a kind of information structure whose integrity is always maintained during transmission on the SDH network, can be regarded as an independent unit (cargo package). It can be flexibly and conveniently added/dropped at any point of the path for synchronous multiplexing and crossconnection processing. Now you might get the idea that VC-4 is in fact the information payload of the STM-1 frame. The process of packing PDH signals into C and adding the corresponding path overhead to form the information structure of VC is called mapping.


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SDH Principle

P-20

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From VC4 to AU4 

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By adding an Administrative Unit Pointer --- AU-PTR before the VC-4, the signal is changed from VC-4 into another information structure--- Administrative Unit AU-4.

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The function of AU-PTR is to indicate the location of the higher order VC within the STM frame. Under the pointer function, the higher order VC is allowed to "float" within the STM frame, i.e. the frequency offsets and phase differences to a certain degree between VC-4 and AU-4 are tolerable. Because the AU-PTR is outside of the payload area and co-located with the section overhead instead. This guarantees that the AU-PTR can be accurately found in the corresponding location. Then the VC-4 can be localized by the AU pointer and disassembled from STM-N signals.

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From AU4 to AUG (N) 

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One or more AUs with fixed locations within the STM frame form an AUG ---Administrative Unit Group. The location of the first byte of the VC-4 with respect to the AU-4 pointer is given by the pointer value. The AU-4 is placed directly in the AUG.

From AUG (N) to STM-N 

The last step is to add corresponding SOH to AU-4 to form STM-N signals. During being multiplexed, the N AUGs are one-byte interleaved into this structure and have a fixed phase relationship with respect to the STM-N.


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SDH Principle

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From 34Mb/s to C3

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Similarly, 34Mb/s signals are first adapted into the corresponding standard container -- C-3 through bit rate justification.

From C3 to VC3 

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After adding corresponding POH, the C-3 is packed into VC-3 with the frame structure of 9 rows × 85 columns.

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SDH Principle

P-22

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From VC3 to TU3 

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For the convenience of locating VC-3 at the receiving and separating it from the high-rate signals, a three-byte pointer, TU-PTR (Tributary Unit Pointer), is added to

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the VC-3 frame. Then what is the function of a tributary pointer? The TU-PTR is used to indicate the specific location of the first byte of the lower order VC within the tributary unit TU. It is similar to an AU-PTR that indicates the location of the first byte of the VC-4 within the STM frame. Actually, the operating principles of these two kinds of pointers are similar. 

From TU3 to TUG3

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The TU-3 frame structure is incomplete. First fill the gap to form the frame structure of TUG3.

From TUG3 to C4, VC4 and STM-N 

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Three TUG-3 can be multiplexed into the C-4 signal structure via byte interleaved multiplexing method. The TUG-3 is a 9-row by 86-column structure. Two columns of stuffed bits are added to the front of the composite structure of 3× TUG-3 to form a C-4 information structure. The last step is to multiplex C-4 into STM-N. This is similar to the process of multiplexing 140Mb/s signals into STM-N signals: C-4-->VC-4-->AU-4-->AUG->STM-N.


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SDH Principle

P-23

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At present, the most frequently used multiplexing method is multiplexing of 2Mb/s signals into STM-N signals. It is also the most complicated method of multiplexing PDH signals into SDH signals.

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From 2Mb/s to C12 

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First, the 2Mb/s signal shall be adapted into the corresponding standard container C-12 via rate adaptation.

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From C12 to VC12 

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notch in the top left corner of each basic frame. Since the VC can be regarded as an independent entity, dispatching of 2Mb/s services later is conducted in unit of VC-12.

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To monitor on a real-time basis the performance of each 2Mb/s path signal during transmission on SDH network, C-12 must be further packed ---- adding corresponding path overhead (lower order overhead)---- to form a VC-12 information structure. The LP-POH (lower order path overhead) is added to the

From VC12 to TU12 

For correct aligning of VC-12 frames in the receiving end, a four-byte TU-PTR is added to the four notches of the VC-12 multi-frame. Then the information structure of the signal changes into TU-12 with 9 rows×4 columns. The TU-PTR indicates the specific location of the start point of the first VC-12 within the multiframe.


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SDH Principle

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From TU12 to TUG2

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Three TU-12 forms a TUG-2 via byte interleaved multiplexing. The TUG-2 has the frame structure of 9 rows by 12 columns.

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From TUG2 to TUG3 

Seven TUG-2 can be multiplexed into a TUG-3 information structure via byte interleaved multiplexing. Note that this information structure formed by the 7× TUG-2 is 9-row by 84-column. Two rows of fixed stuff bits shall be added in front of the structure. The TUG-3 is a 9-row by 86-column structure with the first two columns of fixed stuff.

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From TUG3 to C4, VC4 and STM-N

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The procedures of multiplexing the TUG-3 information structure into STM-N are the same as mentioned before.

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SDH Principle

P-25

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The frame of STM-N consists of three parts

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Section Overhead (including Regenerator Section Overhead ---- RSOH and Multiplex Section Overhead ---- MSOH)

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Administrative Unit Pointer---- AU-PTR

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Information Payload with POH

There are 9 rows and 270N columns in the STM-N frame, which will be transmitted 8000 times per second. Here the value of N equals to 4 for STM-4. 

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9 (rows) X 270 X 4 (columns) X 8 (bits) X 8000 (frame/second) = 622080000 bits/second. It is so called 622 Mbits/s

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SDH Principle

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SDH Principle

P-27

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As mentioned before, the functions of overhead are to implement layered monitoring management for SDH signals. The monitoring is classified into section layer monitoring and path layer monitoring. The section layer monitoring is further classified into regenerator

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section layer monitoring and multiplex section layer monitoring while the path layer monitoring is further classified into higher order path layer and lower order path layer. Thus the layered monitoring for STM-N is implemented. For example, in a STM-16 system, the regenerator section overhead monitors the overall STM-16 signal while the multiplex section overhead further monitors each of the 16 STM-1. Furthermore, the higher order path overhead monitors the VC-4 of each STM-1 and the lower order path overhead can monitor each of the 63 VC-12 in the VC-4. Hence the multistage monitoring functions from 2.5Gb/s to 2Mb/s are implemented.

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SDH Principle

P-28

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Then, how are these monitoring functions implemented? They are implemented via different overhead bytes.

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The overhead of each layer, including RSOH, MSOH, HPOH, and LPOH consists of some

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different bytes for different OAM function. Especially, several overhead bytes e.g. K1 and K2 bytes are very important for maintenance and troubleshooting. According to ITU-T recommendation, there are some overhead bytes reserved for national use.

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SDH Principle

P-29

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Like a pointer, the function of the frame bytes is alignment. The first step is to properly extract each STM-N frame from the received continuous signal stream at the receiver. The function of the bytes A1 and A2 is to locate the start of the STM-N frame. So the receiver

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can align and extract the STM-N frame from the information stream via these two bytes and further align a specific lower-rate signal within the frame via the pointers. 

How does the receiver align the frames via the A1 and A2 bytes? The A1 and A2 have fixed value, i.e. fixed bit patterns: A1: 11110110 (f6H) and A2: 00101000(28H). The receiver monitors each byte in the stream. After detecting 3N successive f6H bytes followed by 3N 26H bytes (there are three A1 and three A2 bytes within an STM-1 frame), the receiver determines that an STM-N frame starts to be received. By aligning the start of each STM-N frame, the receiver can identify different STM-N frames and disassemble them.

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STM-N signals shall be scrambled before being transmitted via the line so that the receiver can extract timing signals from the line. But the A1 and A2 framing bytes shall not be scrambled for the receiver to properly align them. Thus it is convenient to extract the timing from the STM-N signals and disassemble the STM-N signals at the receiver.


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P-30

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If the receiver doesn't receive A1 and A2 bytes within five or more successive frames (625us), i.e. it can't identify the start of five successive frames (identify different frames), it will enter out-of-frame status and generate out-of-frame alarm ---- OOF. If the OOF keeps

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for 3ms, the receiver will enter loss-of-frame status ---- the equipment will generate lossof-frame alarm ---- LOF. Meanwhile, an AIS signal will be sent downward and the entire services will be interrupted. Under LOF status, if the receiver stays in normal frame alignment status again for successive 1ms or more, the equipment will restore the normal status.

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SDH Principle

P-31

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One of the features of SDH is its highly automatic OAM function which can conduct commands issue and performance auto poll to the networks element via NMT Network Management Terminals. SDH has some functions which are not possessed by PDH

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systems, such as real-time service allocation, alarm fault location and on-line performance testing. Where are these OAM data arranged to transmit? The data used for OAM functions, such as sent commands and checked alarm performance data, are transmitted via D1-D12 bytes within the STM-N frame. Thus the D1-D12 bytes provide a common data communication channel accessible to all SDH network elements. As the physical layer of the embedded control channel (ECC), the D1-D12 bytes transmit OAM information among the network elements and form a transmission channel of the SDH management network (SMN).

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The DCC has a total rate of 768kb/s that provides a powerful communication base for SDH network management. D1, D2 and D3 are regenerator section DCC bytes (DCCR) with a rate of 3×64kb/s ＝ 192kb/s and are used to transmit OAM information among regenerator section terminals. D4-D12 are multiplex section DCC bytes (DCCM) with a sum rate of 9×64kb/s=576kb/s and are used to transmit OAM information among multiplex section terminals.


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SDH Principle

P-32

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E1 is part of the RSOH and may be accessed at regenerators. E2 is part of the MSOH and man be accessed at multiplex section terminations. Each of these two bytes provides a 64kb/s orderwire channel for voice communication, i.e. voice information is transmitted via these two bytes.

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The orderwire provides a convenient communication function during maintenance and troubleshooting.

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SDH Principle

P-33

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

This B1 byte is allocated for regenerator section error monitoring (Byte B1 is located in the regenerator section overhead). What is the mechanism for monitoring? First, we'll discuss the BIP-8 parity.



Suppose that a signal frame is composed of 4 bytes: A1=00110011, A2=11001100, A3=10101010 and A4=00001111. The method of providing BIP-8 parity to this frame is to divide it into 4 block with 8 bits (one byte) in a parity unit (each byte as a block because one byte has 8 bits, the same as a parity unit) and to arrange these blocks. Compute the number of "1" over each column. Then fill a 1 in the corresponding bit of the result (B) if the number is odd, otherwise fill a 0. That is, the value of the corresponding bit of B makes the number of "1" in the corresponding column of A1A2A3A4 blocks even. This parity method is called BIP-8 parity. In fact this is an even parity since it guarantees that the number of "1" is even. B is the result of BIP-8 parity for the A1A2A3A4 block.

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The mechanism for B1 byte is: the transmitting equipment processes BIP-8 even parity over all bytes of the previous frame (1#STM-N) after scrambling and places the result in byte B1 of the current frame (2#STM-N) before scrambling. The receiver processes BIP-8 parity over all bits of the current frame (1#STM-N) before de-scrambling and compares the parity result and the value of B1 in the next frame (2#STM-N) after de-scrambling. The different bit means the error block. According to the number of different bits, we can monitor the number of error blocks occurred in 1#STM-N frame during transmission.

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If the B1 of the receive end has detected error blocks, the number of error blocks detected by the B1 will be displayed in receive end performance event RS-BBE (Regenerator Section Background Block Error). When the error bits detected by the receive end exceed a given threshold, the equipment will report corresponding alarms. When the error bit ratio (EBR) is greater than 10E-6, the given alarm is B1-SD. When the error bit ratio (EBR) is greater than 10E-3, B1-EXC (another name B1-OVER) will be given.


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SDH Principle

P-34

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B2 is similar to B1 in operation mechanism except that it monitors the error status of the multiplex section layer. The B1 byte monitors the transmission error of the complete STMN frame signal. There is only one B1 byte in an STM-N frame. There are N*3 B2 bytes in an

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STM-N frame with every three B2 bytes corresponding to an STM-1 frame. The B2 monitoring adopts BIP-24 (three bytes) method, which can at most monitor 24 error blocks one time. 

Since error performance of higher rate signals is reflected via error blocks, the error status of STM-N signals is actually the status of error blocks. As can be seen from the BIP-24 parity method, each bit of the parity result is corresponding to a bit block. So three B3 bytes can at most monitor 24 error blocks from an STM-N frame that occur during transmission (The result of BIP-24 is 24 bits with each bit corresponding to a column of bits

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or



---- a block). If the B2 of the receive end has detected error blocks, the number of error blocks detected by the B2 will be displayed in this end performance event MS-BBE (Multiplex Section Background Block Error). At the same time, M1 will be used to report to the transmit end that error blocks have been detected, and the transmit end will report MS-FEBBE (Multiplex Section Far End Background Block Error) performance event and MS-REI (Multiplex Section Remote Error Indication) alarm. When the error bits detected by the receive end exceed a given threshold, the equipment will report corresponding alarms. When the error bit ratio (EBR) is greater than 10E-6, the given alarm is B2-SD. When the error bit ratio (EBR) is greater than 10E-3, B2-EXC will be given.


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SDH Principle

P-35

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If the B2 of the receive end has detected error blocks, the number of error blocks detected by the B2 will be displayed in this end performance event MS-BBE (Multiplex Section Background Block Error). At the same time, M1 will be used to report to the transmit

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end that error blocks have been detected, and the transmit end will report MS-FEBBE (Multiplex Section Far End Background Block Error) performance event and MS-REI (Multiplex Section Remote Error Indication) alarm. 

This is a message returned to its transmit end by the receive end so that the transmit end can get the receiving error status of the receive end. For STM-N levels this byte conveys the count (in the range of [0, 255]) of interleaved bit blocks that have been detected in error by the BIP-24N (B2). For rates of STM-16 and above, this value shall be truncated to 255.

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SDH Principle

P-36

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Two bytes are allocated for APS signaling for the protection of the multiplex section. For the bit assignments for these bytes and the bit-oriented protocol, please refer to G.783, G.841 (10/98).

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SDH Principle

P-37

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This is an alarm message, returned to the transmit end (source) by the receive end (sink), which means that the receive end has detected an incoming section defect or is receiving the Multiplex Section Alarm Indication Signal (MS-AIS). That is, when the receive end

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detects receiving deterioration, it returns an Multiplex Section Remote defect Indication (MS-RDI) alarm signal to the transmit end so that the later obtains the status of the former. If the received b6-b8 bits of the K2 is 110, it means that this signal is an MSRDI alarm signal returned by the opposite end. If the received b6-b8 bits of the K2 is 111, it means that this signal is an MS-AIS alarm signal received by current end. Meanwhile, the current end is required to send out MS-RDI signal to the opposite end, i.e. insert 110 bit pattern into the b6-b8 of the K2 within the STM-N signal frame to be sent to the opposite end. Not all deterioration results in returning MS-RDI. Current end equipment returns MSRDI only upon receiving R-LOS, R-LOF, and MS-AIS alarm signals.

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SDH Principle

P-38

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

We can use the extended SSM for clock protection. In this case, the different value of bits 1 ~ 4 of byte S1 indicates the different clock source.



Bits 5 to 8 of byte S1 are allocated for Synchronization Status Messages. Table 3-1 gives

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the assignment of bit patterns to the four synchronization levels agreed to within ITU-T. Two additional bit patterns are assigned: one to indicate that quality of the synchronization is unknown and the other to signal that the section should not be used for synchronization. The remaining codes are reserved for quality levels defined by individual Administrations. Different bit patterns, indicating different quality levels of clocks defined by ITU-T, enable the equipment to determine the quality of the received clock timing signal. This helps to determine whether or not to switch the clock source, i.e. switch to higher quality clock source. The smaller the value of S1 (b5-b8), the higher the level of clock

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quality.

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SDH Principle

P-39

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The Section Overhead is responsible for section layer OAM functions while the Path Overhead for path layer OAM functions. Like transporting the cargoes loaded in the container: not only the overall impairment status of the cargoes (SOH) but also the

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impairment status of each cargo (POH) shall be monitored. 

According to the "width" of the monitored path (the size of the monitored cargo) , the Path Overhead is further classified into Higher Order Path Overhead and Lower Order Path Overhead. In this curriculum the Higher Order Path Overhead refers to the monitoring of VC-4 level paths within the STM-N frame. The Lower Order Path Overhead implements the OAM functions for VC-12 path level, i.e. monitoring the transmission performance of 2Mb/s signals within the STM-N frame.

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The Higher Order Path Overhead, consisting of 9 bytes, is located in the first column of the

VC-4 frame.

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SDH Principle

P-40

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The AU-PTR pointer indicates the specific location of the start of the VC-4 within the AU-4, i.e. the location of the first byte of the VC-4, so that the receive end can properly extract VC-4 from the AU-4 according to the value of this AU-PTR. The J1 is the start of the VC-4,

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so the AU-PTR indicates the location of the J1 byte. 

The J1 byte is used to transmit repetitively a Higher Order Path Access Point Identifier so that a path receiving terminal can verify its continued connection to the intended transmitter (this path is under continued connection). This requires that the J1 bytes of the received and transmit ends match. The default transmit/receive J1 byte values of the equipments provided by Huawei Company are “HuaWei SBS”. Of course the J1 byte can be configured and modified according to the requirement.

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The received J1 should match or be same with the expected J1. If not, HP-TIM alarm will

be generated, which perhaps interrupts the service within the VC4 sometimes.

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SDH Principle

P-41

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The B3 byte is allocated for monitoring the transmission error performance of VC-4. Its monitoring mechanism is similar to that of the B1 and B2 except that it is used to process BIP-8 parity for the VC-4 frame.



Once the receive end detects error blocks, the number of error blocks will be displayed in the performance monitoring event ---- HP-BBE (Higher Order Path Background Block

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Error) of the received end. At the same time, G1 (b1-b4) will be used to report to the transmit end that error blocks have been detected, and the transmit end will report HPFEBBE (Higher-order Path Far End Background Block Error) performance event and HP-REI (Higher-order Path Remote Error Indication) alarm.

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When the error bits detected by the receive end exceed a given threshold, the equipment will report corresponding alarms. When the error bit ratio (EBR) is greater than 10E-6, the

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given alarm is B3-SD. When the error bit ratio (EBR) is greater than 10E-3, B3-EXC will be given.

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SDH Principle

P-42

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The C2 is allocated to indicate the composition of multiplexing structure and information payload of the VC frame, such as equipped or unequipped status of the path, the type of loaded services and their mapping method. For example, C2=00H indicates that this VC-4

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path is unequipped. Then the payload TUG-3 of the VC-4 is required to be inserted all "1" --- TU-AIS and the higher order path unequipped alarm ---- HP-UNEQ appears in the equipment. C2=02H indicates that the payload of the VC-4 is multiplexed via a TUG structure multiplexing route. In China, the multiplexing of 2Mb/s signals into VC-4 adopts the TUG structure. To configure the multiplexing of 2Mb/s signals for Huawei equipments, the C2 is required to be configured as TUG structure. 

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The received C2 should match or be same with the expected C2. If not, HP-SLM alarm will be generated, which interrupts the service within the VC4 sometimes.

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SDH Principle

P-43

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The LPOH here refers to the path overhead of the VC-12 that monitors the transmission performance of the VC-12 path level, i.e. monitors the transmission status of 2Mb/s PDH signals within the STM-N frame. Where is the LPOH located within the VC-12? The lower

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order POH is located in the first byte of each VC-12 basic frame. An LP-POH consists of four bytes denoted V5, J2, N2 and K4. Usually, V5 byte is the most important in LPOH. 

The V5 provides the functions of error checking, signal label and path status of the VC-12 paths. So this byte has the functions of the G1, B3 and C2 bytes within the higher order path overhead. If the V5 (b1b2) of the receive end have detected error blocks, the number of error blocks detected by the V5 (b1b2) will be displayed in this end performance event LP-BBE (Lower-order Path Background Block Error). At the same time, V5 (b3) will be used to report to the transmit end that error blocks have been detected, and the transmit end

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will report LP-FEBBE (Lower-order Path Far End Background Block Error) performance event and LP-REI (Lower-order Path Remote Error Indication) alarm. When the error bits detected by the receive end exceed a given threshold, the equipment will report corresponding alarms. When the error bit ratio (EBR) is greater than 10E-6, the given alarm is BIP-SD. When the error bit ratio (EBR) is greater than 10E-3, BIP-EXC will be given.

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Bit 8 of the V5 is allocated for the VC-12 Path Remote Defect Indication. An LP-RDI (Lower

M

Order Path Remote Defect Indication) is sent back to the source if either a TU-12 AIS signal or signal failure condition is being detected by the sink. Notes: In this curriculum, RDI is called remote deterioration indication or remote defect indication.


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P-44

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The function of the pointers is aligning via which the receiver can properly extract the corresponding VC from the STM-N and then disassemble the VC and C packages and extracts the lower rate PDH signals, i.e. directly drop lower rate tributary signals from the STM-N signal.

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What is aligning? Aligning is a procedure by which the frame offset information is incorporated into the Tributary Unit or the Administrative Unit, i.e. via the Tributary Unit Pointer (or Administrative Unit Pointer) attached to the VC to indicate and determine the start of the lower order VC frame within the TU payload ( or the start of the higher order VC frame within the AU payload). When relative differences occur in the phases of the frames and make the VC frames "float", the pointer value will be justified to ensure that it constantly and properly designates the start of the VC frame. For a VC-4, its AU-PTR

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indicates the location of the J1 byte while for a VC-12; its TU-PTR indicates the location of the V5 byte. The TU pointer or AU pointer provides a method of allowing flexible and dynamic alignment of the VC within the TU or AU frame because these two pointers are able to accommodate differences, not only in the phases of the VC and the SDH, but also in the frame rates.


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SDH Principle

P-45

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The AU-PTR, located in row 4 of columns 1 to 9 within the STM-1 frame, is used to indicate the specific location of the fist byte J1 of the VC-4 within the AU-4 payload so that the receiver can properly extract the VC-4. The AU-4 pointer provides a method of

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allowing flexible and dynamic alignment of the VC-4 within the AU-4 frame. Dynamic alignment means that the VC-4 is allowed to "float" within the AU-4 frame. Thus, the pointer is able to accommodate differences, not only in the phases of the VC-4 and the SOH, but also in the frame rates. The pointer contained in H1 and H2 designates the location of the byte where the VC-4 begins. The last ten bits (bits 7-16) of the pointer word carry the pointer value.

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SDH Principle

P-46

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The TU pointer is used to indicate the specific location of the first byte V5 of the VC-12 within the TU-12 payload so that the receiver can properly extract the VC-12. The TU pointer provides a method of allowing flexible and dynamic alignment of the VC-12 within

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the TU-12 multi-frame. The TU-PTR is located in the bytes denoted V1, V2, V3 and V4 within the TU-12 multi-frame. 

The TU pointer of TU3 consists of H1, H2 and H3. Their function is similar to that of AUPTR.

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SDH Principle

P-47

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

K2 byte is used to monitor the status of MS, which might generate MS-AIS or MS-RDI alarm.



If the receiver doesn't receive A1 and A2 bytes within five or more successive frames

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(625us), i.e. it can't identify the start of five successive frames (identify different frames), it will enter out-of-frame status and generate out-of-frame alarm ---- OOF. If the OOF keeps for 3ms, the receiver will enter loss-of-frame status ---- the equipment will generate lossof-frame alarm ---- LOF. Meanwhile, an AIS signal will be sent downward and the entire services will be interrupted. Under LOF status, if the receiver stays in normal frame alignment status again for successive 1ms or more, the equipment will restore the normal status.

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The BIP-8 parity.

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SDH Principle

P-48

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SDH Principle

P-49

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WDM Principle

P-1

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Contents

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WDM Overview……………………………...…………………………...…..……..Page4

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WDM Transmission Media .....................…………………………….……..……Page16 WDM Key Technologies ………………………………………………......………Page24 Technology Specifications for WDM System..................................................... Page48

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WDM Principle

P-2

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About this course: 

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This course mainly introduces the basic knowledge of WDM technologies, expounds key technologies and optical transmission specification of WDM. Through this course, you will have a relatively complete understanding of the WDM knowledge and the development orientation of optical transmission networks.

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WDM Principle

P-3

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Reference:  

OTC000003 WDM principle

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ITU-T G.694.1 and G.694.2 (about the wavelength distribution)



ITU-T G.671 (about the optical passive components)

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ITU-T G.652 , G.653 and G.655 (about the fiber)

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WDM Principle

P-4

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WDM Principle

P-5

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

SDM increases the transmission capacity linearly by adding the number of optical fibers, and the transmission equipment will be increased linearly, too.



TDM keeps the same transmission medium but increases the bit rate. The equipment is getting more and more complicated and expensive. Additionally, the maximum transported capability over a fiber pair is in the range of a few 10Gbps.



The way to scale to higher transported capacity is WDM. This technology keeps the same fiber, the same bit rate, but uses multiple colours to multiply transported capacity.



WDM is widely used in the national and metro backbone transmission systems.

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WDM Principle

P-6

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Legend:  Freeway: Fiber  Patrol Car: Supervisory Signal  Gas Station: Optical Relay  Gray Car: Client Service  Colored Car: Service in different channels (wavelength)  Driveway: Optical Wavelength Wave Division Multiplexing is a technology that utilizes the properties of refracted light to both combine and separate optical signals based on their wavelengths within the optical spectrum.

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WDM Principle

P-7

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The Greek letter lambda (  ) , is often used to designate individual wavelengths.



Key word in the content is specific wavelength. How specific ? Please refer to ITU-T series recommendations in chapter 4.



WDM allows for a more efficient use of existing fiber by providing multiple optical paths along a single (pair of) fiber (s).



WDM allows for a greater range of protocol transmission better suited than legacy network for data centric applications. (E.g.. GE, ESCON, Fiber Channel, D1 video)

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WDM Principle

P-8

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

OTU: Access the client service and convent the wavelength complied with ITU standards.



OMU: Multiplex several services with different wavelength into one main path signal



ODU: Demultiplex one main path signal into several individual signals.

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OA: Amplifies the optical signal.

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OLA: Optical Line Amplifier

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OSC: Optical Supervisory Channel



ESC: Electrical Supervisory Channel

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WDM Principle

P-9

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

Unidirectional WDM system adopts two optical fibers. One only implements the transmission of signals in one direction while the other implements the transmission of the signals in the opposite direction.



This tansmission mode is widely used in the worldwide.

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WDM Principle

P-10

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

Bi-directional wave WDM system utilizes only one optical fiber. The single fiber transmits optical signals in both directions simultaneously, and the signals in the different directions should be assigned on different wavelengths



Note:

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

To MUX/DEMUX the signals in one fiber, circulator is recommended.



This mode is usually used in the CWDM system to reduce the cost

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WDM Principle

P-11

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

Integrated system does not adopt the wavelength conversion technology, instead, it requires that the wavelength of the optical signals at the multiplex terminal conforms to the specifications for the WDM system



The optical interface in the client equipment that could provide standard wavelength is called colored interface. Huawei series OSN products could support this function

 Thought: 

s e c r u o s e R

Can some channels use OTU and some channels use colored interface?

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WDM Principle

P-12

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t t :h



Up to know the capacity is 1920Gbps at most.



Data Transparency Transmission: 

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// : p

s e c r u o s e R

WDM doesn’t change the structure or any byte in the frame for the client signal



Long Haul transmission: 5000km without REG / 230km long hop.



Smooth expansion: modularization and no affect the existing services

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WDM Principle

P-13

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

t t :h



No amplification=a lower-cost system and distance-limited system

Comparison between CWDM and DWDM

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M

s e c r u o s e R

Fewer channels=cheaper hardware

Types Channel Spacing

or

// : p

CWDM greatly reduces the system cost while providing certain amount of wavelengths and transmission distance within 100 km. 



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CWDM 20nm

DWDM 100GHz/50GHz/25GHz C-band: 1529nm~1561nm L-band: 1570nm~1603nm

Band

1311~1611nm

Capacity Laser

16 x 2.5Gb/s = 40G Un-cooled Laser

192 x 10Gb/s = 1920G Cooled Laser

Cost

70%

100%

Application

100km

5000km


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WDM Principle

P-14

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

t t :h

Fill in the blanks:

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1. WDM System includes:________, _________, _________ and __________;

s e c r u o s e R

2. CWDM system could use optical amplifiers (True or False) __________; 3. ESC means____________________________________. Need additional wavelength to transmit in the fiber (True or False) _________. 4. Single fiber bidirectional transmission (can or can not )_________ use the same wavelength for transmitting and receiving.

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WDM Principle

P-15

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

OTU, MUX/DeMUX, OA,OSC



False



Electrical Supervisory Channel,False



Can not

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WDM Principle

P-16

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Objectives for this chapter:

// : p



List the characteristics of the fiber



Classify different types of the fiber



Outline the methods to against the factors

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WDM Principle

P-17

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

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An optical fiber consists of two different types of solid glass —the core and cladding—that are mixed with specific elements to adjust their refractive indices. The difference between the refractive indices of the two materials causes most of the transmitted light to bounce off the cladding and stay within the core. The critical angle requirement is met by controlling the angle at which the light is injected into the fiber. Two or more layers of protective coating around the cladding ensure that the glass can be handled without damage.

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N1 and N2, which one is larger ?

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WDM Principle

P-18

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

Band

Wavelength



Original

1260~1360



Extended

1360~1460

100



Short

1460~1525

65



Conventional

1525~1565

40



Long

1565~1625

60



Ultra long

1625~1675

50

M

or

// : p

Bandwidth (nm)

s e c r u o s e R

100

n r a

Combining the above losses, the attenuation constant of single mode fiber at 1310nm and 1550nm wavelength areas is 0.3~0.4dB/km (1310nm) and 0.17~0.25dB/km (1550nm), respectively. As defined in ITU-T Recommendation G.652, the attenuation constant at 1310nm and 1550nm should be less than 0.5dB/km and 0.4dB/km, respectively.

e L e



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WDM Principle

P-19

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Dispersion in fiber refers to a physical phenomenon of signal distortion caused when various modes carrying signal energy or different frequencies of the signal have different group velocity and disperse from each other during propagation

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WDM Principle

P-20

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

G.652 fiber is currently a single mode fiber for widely use, called 1310nm property optimal single mode fiber and also called dispersion unshifted fiber



G.653 fiber is called dispersion shifted fiber or 1550nm property optimal fiber. By designing the refractive index cross section, the zero dispersion point of this kind of fiber is shifted to the 1550nm window to match the minimum attenuation window. This makes it possible to implement ultrahigh speed and ultra long distance optical transmission



G.655 fiber, a nonzero dispersion shifted single mode optical fiber, is similar to G.653 fiber and preserves certain dispersion near 1550nm to avoid four-wave mixing phenomenon in DWDM transmission. It is suitable for DWDM system applications

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WDM Principle

P-21

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

DCF is one special kind of optical fiber, with the negative dispersion at 1550nm window



The dispersion coefficient is -90~-120ps/nm.km



DCF can counter act positive dispersion while bring new insertion loss and increasing of PMD

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WDM Principle

P-22

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

t t :h

Fill in the blanks:

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1. The attenuation coefficient of G.652 fiber is __________; approximately ________ for engineering planning

s e c r u o s e R

2. The dispersion coefficient of G.655 at 1550nm window is_______________ 3. The dispersion coefficient of G.652 at 1310nm window is__________; at 1550nm window is___________

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WDM Principle

P-23

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t t :h



Coating, Cladding, Core



G.652, G.653, G.655



Attenuation, Dispersion, Nonlinear effect

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WDM Principle

P-24

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WDM Principle

P-25

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WDM Principle

P-26

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WDM Principle

P-27

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

Output laser is controlled by input current. The variation of the modulation current causes the variation of output wavelength



This variation, called modulation chirp, is actually a kind of wavelength (frequency) jitter inevitable for direct modulation of the sources. The chirp broadens the bandwidth of the emitting spectrum of the laser, deteriorates its spectrum characteristics and limits the transmission rate and distance of the system



Transmission rate is limited to 2.5Gbit/s, and transmission distance is less than 100km



Similar Specification –This kind of modulator is Widely used in CWDM system

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WDM Principle

P-28

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

EA modulator adopts different structure, use stable DC current to let LD output a standard wavelength (complied with ITU-T). EA module act as a door that open only happens to the current change. In this way, the information is modulated into the wavelength



Less chirp = Support long haul transmission (2.5Gb/s > 600km)



High Dispersion tolerance (2.5Gb/s: 7200~12800ps/nm)



Most widely used in DWDM

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WDM Principle

P-29

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This modulator separates the light input into two equal signals which enter the two optical branches of the modulator respectively. These two optical branches employ an electrooptical material whose refractive index changes with the magnitude of the external electrical signal applied to it. Changes of the refractive index of the optical branches will result in the change variation of the signal phases. Hence, when the signals from the two branches recombine at the output end, the combined optical signal is an interference signal with varying intensity. With this method, the frequency chirp of the separated external modulated laser can be equal to zero

g n ni

s e c r u o s e R



Long dispersion limited distance



High cost with good performance



Negligible chirp



Not widely used

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WDM Principle

P-30

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

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As a maturing technology, direct modulator and indirector modulator are widely used in WDM system

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WDM Principle

P-31

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The EDFA amplifier is widely used in WDM system

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WDM Principle

P-32

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

t t :h

Principle: 





r a le

g n ni

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The outer electrons of Er ions have 3 energy levels, where E1 is the basic state energy level, E2 is the metastable state energy level and E3 is the high energy level

s e c r u o s e R

When high-energy pump lasers are used to excite the EDF, lots of bound electrons of the erbium ions are excited from E1 to E3 level, then soon dropped to the E2 level via a non-radiation decay process (i.e. no photon but heat is released) When a signal with the wavelength of 1550nm passes through this erbium-doped fiber, particles in the metastable state are transited to the basic state via stimulated radiation and generate photons identical to those in the incident signal light

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WDM Principle

P-33

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

TAP is used to spilt out a little part of energy and send it to the PD to detection



ISO is used to make sure the signal transmit in one direction



Pump laser has two type: with 980nm and with 1480nm



If we want to get a high gain, we could cascade EDF and pumping laser

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WDM Principle

P-34

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





t t :h

Advantage:

// : p

Fortunately, 1550nm is in the low attenuation window, the emergence of EDFA greatly activate the development of WDM

Disadvantage: 

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Gain un-flatness

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WDM Principle

P-35

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

If we cannot control the gain, optical surge generates



With AGC function:



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g n ni

s e c r u o s e R



When add wavelengths from 1 to 40, the gain will be not changed



When drop wavelengths from 40 to 1, the gain will be not changed also

Key Component is the DSP that makes the nonlinear calculation

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WDM Principle

P-36

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

Principle:



Fiber has wide SRS gain spectrum and a wide gain peak around a frequency 13THz lower than that of the pumping light. If a weak signal and a strong pumping light wave are transmitted through the fiber at the same time, and the wavelength of the weak signal is set within the Raman gain bandwidth of the strong pumping light, the weak signal can be amplified. Such SRS-based OA is call Raman optical amplifier. Raman optical amplifier’s gain is the switch gain, that is, the difference between the output power when the amplifier is on and that when the amplifier is off

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WDM Principle

P-37

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

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

The gain wavelength is determined by the pumping light wavelength



The gain medium is the transmission fiber itself, low noise





t t :h

Advantage:

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s e c r u o s e R

As the amplification is distributed along the fiber with the comparatively low signal power, it reduces the interference from non-linear effect, especially FWM effect

Disadvantage:

g n ni



High power is harmful for body



Be careful when put operation on Raman

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WDM Principle

P-38

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

t t :h

According to its application: 





r a le

g n ni

// : p

BA: Booster amplifier, mainly used in the transmit end. For the hardware description, you will see OBU card

s e c r u o s e R

LA: Line amplifier, mainly used in the amplifier station, could be recognized as BA+PA. For the hardware description, you will see OAU card PA: Pre-amplifier, mainly used in the receive end. For the hardware description, you will see OPU card

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WDM Principle

P-39

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

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For all the optical lights are bidirectional, the mechanisms of multiplexer and demultiplexer are the same. Here in after we just discuss about the multiplexer, if you reverse the direction, it could also be considered as a demultiplexer

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WDM Principle

P-40

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

Film Filter offers good stability and isolation between channels at moderate cost, but with a high insertion loss



So the number of dropping wavelength is limited

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WDM Principle

P-41

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

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The waveguides are connected to cavities at the input and output. When the light enters the input cavity, it is diffracted and enters the waveguide array. There the optical length difference of each waveguide introduces phase delays in the output cavity, where an array of fibers is coupled. The process results in different wavelengths having maximal interference at different locations, which correspond to the output ports

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WDM Principle

P-42

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OSC is often used in the backbone wavelength system, and ESC is normally used in metropolitan system

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WDM Principle

P-43

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

Pumping wavelength of OA: 980nm or 1480nm.



1310nm already defined by ITU-T for future use.



OA fails, all signal lost, requires the supervisory signal continue to transmit alarms and other indications.



The receive sensitivity of the OSC unit is very good, up to -48dBm.

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WDM Principle

P-44

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

FA: Frame alignment



E1 E2 : Orderwire



ALC: Automatic Level Control.



F1 F2 F3 : transparent serials data



D1-D12: DCC bytes, data communication channel

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WDM Principle

P-45

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

The optical transponder unit (OTU) multiplexes the supervisory information into the service channel for transmission



The ESC reduces the investment of the OSC. It also deletes the insertion loss of the FIU. This lowers the cost and the power budget of optical channels

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WDM Principle

P-46

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Fill in the blanks:

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1. EDFA means:______________________; its pumping wavelength is___________; We can calculate noise figure by _________。

s e c r u o s e R

2. AWG means:______________________; TFF means:________________________; 3. OSC signal’s frame structure is_____________, (can, can not) by amplified by OA. 4. ESC support OLA station ?_______(True, False)

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WDM Principle

P-47

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

LD, EA, M-Z



EDFA, Raman



TFF, AWG



OSC, ESC

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WDM Principle

P-48

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WDM Principle

P-49

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ITU-G.692 – Optical Interfaces for Multi-Channel Systems with Optical Amplifiers 

This recommendation specifies multi-channel optical line system interfaces for the purpose of providing future transverse compatibility among such systems. The current recommendation defines interface parameters for systems of four, eight, and sixteen channels operating at bit rates of up to STM-16 on fibers, as described in Recommendations G.652, G.653, and G.655 with nominal span lengths of 80 km, 120 km, and 160 km and target distances between regenerators of up to 640 km. A frequency grid anchored at 193.1 THz with inter-channel spacing at integer multiples of 50 GHz and 100 GHz is specified as the basis for selecting channel central frequencies

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WDM Principle

P-50

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







S1…Sn: The reference points on the fiber at transmitter optical output connector in channels 1…n

s e c r u o s e R

RM1 RMn: The reference points on the fiber at OM/OA optical input connector in channels 1…n MPI-S: A reference point on the optical fiber just behind the OM/OA optical output connector

g n ni

S': A reference point on the optical fiber behind the optical output connector of the optical line amplifier

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The WDM system in the above figure has the following reference points: 

or

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



R': A reference point on the optical fiber in front of the optical input connector of the optical line amplifier MPI-R: A reference point on the optical fiber in front of the OA/OD input optical connector



SD1…SDn: The reference points at the OA/OD optical output connector



R1…Rn: The reference points at receiver optical transmitter input connector


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WDM Principle

P-51

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WDM Principle

P-52

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WDM Principle

P-53

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OTN Principle

P-1

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

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Contents

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Optical transport hierarchy ………………...………………………………………….Page4

s e c r u o s e R

OTN interface structure………………………...………………………………………Page8 Multiplexing/mapping principles and bit rates………..……...……………………...Page15 Overhead description…………………………………..………………………..……Page28 Maintenance signals and function for different layers………….…………………..Page48

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Alarm and performance events ……………………………………..……………….Page59

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OTN Principle

P-2

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This Course is mainly based on：

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

ITU-T G.872

Architecture of optical transport networks



ITU-T G.709

Interfaces for the Optical Transport Network (OTN)



ITU-T G.874

Management aspects of the optical transport network element



ITU-T G.798

Characteristics of optical transport network hierarchy equipment

s e c r u o s e R

functional blocks

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OTN Principle

P-3

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OTN Principle

P-4

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Objectives for the first chapter:

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

Describe the features of OTN



Outline the protocols which supports OTN system

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OTN Principle

P-5

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

One important feature of OTN is that the transmission setting of any digital customer signal is independent of specific features of the customer, that is, independence of customer.



According to the requirements given in Rec. G.872.



The optical transport network supports the operation and management aspects of optical

s e c r u o s e R

networks of various architectures.

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OTN Principle

P-6

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Compared with SDH/SONET, the benefits of OTN are as follows: 

Strong scalability of the capacity: The cross-connect capacity can be expanded to dozens of T bit/s.

s e c r u o s e R



The customer signal transparency covers payload and clock information.



The asynchronous mapping eliminates restriction on the synchronization in the whole network, with stronger FEC. The simplified system design can decrease the networking costs.





r a e

Compared with the traditional WDM:

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Up to 6-level TCM monitoring management capability.

 

Effective monitoring capability: OAM&P and network survivability

Flexible optical/electrical grooming capability, carrier-class, manageable, and operable networking capability.


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P-7

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G.874, management features of optical transmission NE, describes the management feature of the OTN NE and transmission function of one or more network layers in the OTN. The management of the optical layer network is separated from the management of

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the customer layer network. Therefore, the same management method that is independent of the customer can be used. G.874 defines fault management, configuration management, billing management, and performance monitoring. G.874 describes the management network architecture model between the NE EMS and optical NE equipment management functions. 

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G.798, feature of equipment function block of the optical transport network, defines the function requirements of the optical transmission network in the NE equipment.

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G.709, OTN interface, defines OTM-n signal requirements of OTN, including OTH, support

of multi wavelength optical network overhead, frame structure, bit rate, and format of mapping customer signals. G.872, OTN architecture, defines the relation between OTN hierarchical architecture, feature information and customer/service layer, and the function description of the network topology and layer network.


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OTN Principle

P-8

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

Draw the frame structure of OTN;



Outline the function of each part in OTN frame;



Brief introduce the difference between OTM-n.m and OTM-0.m;



Describe how does a client signal are encapsulated to OTN frame.

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OTN Principle

P-9

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

OPUk: Optical channel Payload Unit-k



ODUk: Optical channel Data Unit-k



OTUk: completely standardized Optical channel Transport Unit-k



OTUkV: functionally standardized Optical channel Transport Unit-k



OCh: Optical Channel with full functionality



OChr: Optical Channel with reduced functionality



OMS: Optical Multiplex Section



OTS: Optical Transmission Section



OPS: Optical Physical Section



OTM: Optical Transport Module

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OTN Principle

P-10

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

Now we introduce the basic information contained in OTM-n.m, OTM-nr.m, and OTM-0.m. The rates and frame formats comply with ITU-T G.709 recommendations.



The figure on the right shows the composition of the OTM-n.m signals of the OTM interface with complete function. The OTM-n.m is composed of up to n multiplexing wavelengths and OTM overhead signals that support the non-associated overhead. Where, m can be 1, 2, 3, 12, 23, or 123.”m=1” indicates the bearer signals are OTU1/OTU1V. m=2: indicate the bearer signals are OTU2/OTU2V. “m=3” indicates the bearer signals are OTU3/OTU3V. “m=12” indicates partial bearer signals are OTU1/OTU1V and partial bearer signals are OTU2/OTU2V. “m=23” indicates partial bearer signals are OTU 2/OTU2V and partial bearer signals are OTU3/OTU3V. “m=123” indicates partial bearer signals are OTU 1/OTU1V, partial bearer signals are OTU2/OTU2V, and partial bearer signals are OTU3/OTU3V. The physical optical feature specifications of OTM-n.m signals are determined by the suppliers. The recommendations do not have specific specifications.

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The signal mapping or multiplexing of each layer is introduced in the above. Here, we will not repeat it.



Note: The optical layer signal OCh is composed of OCh payload and OCh overhead. After the OCh is modulated to the OCC, multiple OCC time division multiplexes (TDM) constitute the OCG-n.m unit. OMSn payload and OMSn overhead constitute the OMU-n.m. OTSn payload and OTSn overhead constitute the OTM-n.m unit.



The overhead and generic management information of the optical layer units constitute the OTM overhead signal (OOS), which is transmitted by 1-channel independent OSC in the non-associated overhead.



The overhead of electrical layer units such as OPUk, ODUk, and OTUk are the associated channel overheads, which are transmitted together with the payload.


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OTN Principle

P-11

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The OTM-nr.m signals are composed of up to n optical channel multiplexing, and does not support the non-associated overhead. At present, m of OTM-16r.m can be 1, 2, 3, 12, 23, or 123, where, the physical optical feature specifications of OTM-16r.1 and OTM-16r.2 are

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defined in G959.1 of ITU-T. The physical optical feature specifications of other four signals are in need of the further study. 

The electrical layer signal structures of OTM-nr.m and OTM-n.m are the same. The optical layer signals do not support the non-associated overhead OOS, without the optical monitor channel. Therefore, it is called the OTM interface with the reduced function.

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OTN Principle

P-12

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OTM-0.m is composed of the single optical channel. It does not support the associated overhead OOS and is without specific wavelength configuration. Only one optical channel is contained; therefore, m can be 1, 2, or 3 only. The physical optical feature specifications

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of OTM-0.1, OTM-0.2, and OTM-0.3 are defined in G.959.1 and G.693. 

The electrical layer signal structure of three OTM interfaces are the same, the electrical layer signals are monitored through the associated overhead. The difference is: The OTMn.m optial layer signals supports the transmission of the non-associated overhead through 1-channel OSC. The OTM-nr.m and OTM-0.m do not support the optical layer overhead.

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OTN Principle

P-13

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OTN Principle

P-14

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Now, we introduce the OTN network interface. As shown in the figure, the interface between user A and network operator B is the UNI, and the interface between different OTN networks is NNI. G.872 defines two OTN network interfaces: IrDI and IaDI. The IrDI

s e c r u o s e R

refers to the network interface between different operators, for example, the interface between operators B and C as shown in the figure. The IaDI refers to the network interface within the same operator. According to the suppliers, the IaDI includes the interface between different supplier equipment IrVI (for example, the interface between supplier equipment X and supplier equipment Y in operator B’s domain as shown in the figure) and the subnet interface of the same supplier equipment IaVI (for example, the interface between supplier equipment X subnet and supplier equipment Y subnet).

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The OTUk and OTUkV provide the transparent network connection between 3R

regenerator points. The OTUk is applicable to OTM IrDI and IaDI. The OTUkV is applicable to OTM IaDI only.


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OTN Principle

P-15

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

Draw the mapping route of OTM;



List the rate of all types of OTUk,ODUk and OPUk signals;



Describe how does a lower rate ODUk multiplex to a higher rate ODUk.

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OTN Principle

P-16

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OTN Principle

P-17

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OTN Principle

P-18

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OTN Principle

P-19

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OTN Principle

P-20

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OTN Principle

P-21

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Now we introduce the frame rate of OPU/ODU/OTU. The size of OTUk is fixed, that is, OTU1, OTU2, and OTU3 are 4-line and 4080-column. For OTU1 frames, from Column 1 to Column 16, there are OTU1, ODU1, and OPU1 overhead. From Column 17 to Column 3824 (with 3808 columns in total), there are customer signals. From column 3825 to column 4080 (with 256 columns in total), there are FEC areas. Assume the customer signals are STM-16 SDH signals, the rate is 2 488 320kbit/s, the calculations are as follows:

s e c r u o s e R



Customer signal size/OTU frame size = Customer signals rate / nominal OTU frame rate



3808/4080 = 2 488 320 / nominal OTU1 frame rate



That is, nominal OTU1 frame rate = 255/238 x 2 488 320 kbit/s



For OTU2 frames, four ODU1s are combined to ODTUG2 through the TDM. Four ODU1s operate as the OPU2 payload, occupying 3808 columns. In OPU2 payload, there are 16 columns of OTU1, ODU1, and OPU1 overhead. Therefore, the customer signals are 3792 columns. The calculation is as follows:

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3792/4080 = 2 488 320 x 4 / nominal OTU2 frame rate



That is, nominal OTU2 frame rate = 255/237 x 9 953 280 kbit/s



The nominal OTU3 frame rate = 255/236 x 39 813 120 kbit/s



For OTU1/2/3 frame rate, the conclusion is as follows:



OTUk rate = 255/(239-k) x STM-N frame rate



Where, k=1, 2, 3 correspond to the frame rate of STM-16, STM-64, and STM-256 respectively.



The OTU bit rate tolerance is ± 20 ppm.


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OTN Principle

P-22

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NOTE – The nominal ODUk rates are approximately: 2 498 775.126 kbit/s (ODU1), 10 037 273.924 kbit/s (ODU2), 40 319 218.983 kbit/s (ODU3), 104 794 445.815 kbit/s (ODU4) and 10 399 525.316 kbit/s (ODU2e).

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OTN Principle

P-23

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NOTE – The nominal OPUk payload rates are approximately: 1 238 954.310 kbit/s (OPU0 Payload), 2 488 320.000 kbit/s (OPU1 Payload), 9 995 276.962 kbit/s (OPU2 Payload), 40 150 519.322 kbit/s (OPU3 Payload), 104 355 975.330 (OPU4 Payload) and 10 356

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012.658 kbit/s (OPU2e Payload). The nominal OPUk-Xv Payload rates are approximately: X × 2 488 320.000 kbit/s (OPU1-Xv Payload), X × 9 995 276.962 kbit/s (OPU2-Xv Payload) and X × 40 150 519.322 kbit/s (OPU3-Xv Payload).

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OTN Principle

P-24

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OTN Principle

P-25

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OTN Principle

P-26

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First of all, we introduce how four ODU1 multiplex to one ODU2. Use the frame alignment overhead to expand one ODU1 signal, and use the JOH to map them asynchronously to the optical channel data tributary units 1 and 2 (ODTU12). Then, four ODTU12 is combined

s e c r u o s e R

to ODTUG2 in the TDM mode, and ODTUG2 is mapped to the OPU2. Finally, the OPU2 is mapped to the ODU2.

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OTN Principle

P-27

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

The second TDM: Multiplex the ODU1 signal or ODU2 to ODU3 signals, or ODU1 and ODU2 are multiplexed to ODU3 signals.



The multiplexing includes two steps:



Procedure 1: For the ODU1 signal, use the frame alignment overhead to expand one ODU1 signal, and asynchronously map to the ODTU13 by using the JOH.



Procedure 2: For the ODU2 signals, use the frame alignment overhead to expand one ODU2 signal, and use the JOH to asynchronously map them to the ODTU23; then, j ODTU23 (0  j  4) and (16-4j) ODTU13 signal are combined to ODTUG3 in the TDM mode. Then, ODTUG3 is mapped to the OPU3. Finally, the OPU3 is mapped to the ODU3. In this way, the TDM from ODU1 and ODU2 to ODU3 is completed.

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OTN Principle

P-28

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

List the overheads in OTN frame;



Describe the function of each overhead.

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OTN Principle

P-29

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

The OPUk is in the area from row 15 to row 3824, where, OPUk overhead area is from column 15 to column 16, OPUk payload area is from column 17 to column 3824, customer signals are in the OPUk payload area.



The ODUk is in the block structure with 4 lines and 3824 columns, which is composed of ODUk overhead and OPUk, where ODUk overhead area is from row 1 to row 4 and from

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column 1 to column 14. The frame alignment overhead area is from column 1 to column 7 in the first line. Column 8 to 14 in the first line are all-zero. 

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The OTUk overhead area is from column 8 to column 14 in the first line, and the FEC area is from column 3825 to column 4084 (256 columns in total) on the right of the frame. The frame alignment overhead area is from Column 1 to column 7 of the first line in the frame header.

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

The customer signal rate corresponding to OTU1/2/3 is respectively 2.5G/10G/40Gbits/s. The OTUk frame structure of each level is the same. The OTUk signals at the ONMI must have the sufficient bit timing information. Therefore, the OTUk provides the scramble function, to construct an appropriate bit pattern by using a scrambler, with the avoidance of long “1” or long “0” series. With the consideration of the framing, the OTUk overhead FAS should not be scrambled. The scrambling operation is performed after FEC calculation and insertion of OTUk signals.



The transmission sequences of the bytes in the OTUk frame is from left to right, from top down

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OTN Principle

P-30

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

The figure shows the overall electrical layer overhead, include frame alignment overhead, OTUk layer overhead, ODUk layer overhead, and OPUk layer overhead.



The frame alignment overhead is used for the framing. It is composed of 6-byte frame

s e c r u o s e R

alignment signal overhead FAS and 1-byte multi-frame alignment overhead MFAS. 

OTUk layer overhead supports the transmission operation function connected through one or more optical channel. It is composed of 3-byte SM, 2-byte GCC0, and 2-byte RES. It is terminated at the OTUk signal assembly and dissemble places.



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ODUk layer overhead is used to support the operation and maintenance of the optical channel. It is composed of 3-byte PM for end-to-end ODUk channel monitoring, 6-level TCM1-TCM6 with 3 bytes respectively, 1-byte TCMACT, 1-byte FTFL, 2-byte EXP, 2-byte GCC1, 2-byte GCC2, 4-byte APS/PCC, and 6-byte reservation overhead. The ODUk

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overhead is terminated at the ODUK assembly and disassemble places. TC overhead is added at the source, and is terminated at the sink. OPUk overhead is used to support the customer signal adaptation. It is composed of 1byte PSI, 3-byte JC, 1-byte NJO, and 3-byte reservation overhead. It is terminated at the OPUk assembly and disassemble places.


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OTN Principle

P-31

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Frame Alignment Signal (FAS) is used for the frame alignment and positioning, with the length of six bytes. It is located in Column 1 to Column 6 of Line 1. The contents are shown in the figure: three OA1 plus three OA2 series. The value of OA1 is 0xF6, and the

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value of OA2 is 0x28.

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OTN Principle

P-32

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Multi-Frame Alignment Signal (MFAS) follows the FAS. Some OTUk and ODUk overheads, for example, TTI, should cross multiple OTUk/ODUk frames. These overheads must implement the OTUk/ODUk frame alignment and multi-frame alignment processing. The

s e c r u o s e R

MFAS is used for the multi-frame alignment. 

The length of the overhead is one byte, and is located in Line 1 Column 7.



The value of the MFAS bytes increases with the increase of the OTUk/ODUk basic frame number, from 0 to 255 (with up to 256 basic frames). For the overhead of each multiframe structure, the length can be adjusted. For example, if an overhead uses the multiframe structure with 16 basic frames, bit1-bit4 are not calculated when the multi-frame signals are extracted.

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OTN Principle

P-33

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

The SM overhead is composed of three bytes.



The trail trace identifier (TTI), with the length of one byte, is located in the first byte of the SM overhead. It is used to transmit 64-byte OTUk-level trail trace identifier signals. The

s e c r u o s e R

content sequence of 64 bytes are: 

Byte 0 includes SAPI[0] character, with the fixed value of all zeroes.



Byte 1-byte5 include 15-character SAPI.



Byte 16 includes DAPI[0] character, with the fixed value of all zeroes.



Byte 17-byte 31 include 15-character DAPI.



Byte 32- byte 63 are the contents designated by the operator.

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The 64-byte TTI signal should align with the OTUk multi-frame. Transmit for four times in each multi-frame. Each multi-frame contains 256 frames.

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OTN Principle

P-34

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Bit Interleaved Parity-8 (BIP-8) byte is used for the detection of the OTUk-level bit error detection. The code is in the even parity inserted among bits. Its length is one byte, located in the second byte of the SM overhead. For BIP8 parity, calculate the bit in the whole

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OPUK frame area of the No.i OTUk frame to obtain the OTUk BIP-8. Insert the results to No.(i+2) OTUk frame OTUk BIP-8 overhead position. In No.(i+2) frame, as shown in the figure, compare this value with the DIP8 calculation results of the current frame. If both values mismatch, detect the bit error block of the near end.

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OTN Principle

P-35

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Backward Error Indication (BEI) and Backward Incoming Alignment Error (BIAE) are used to return the detected bit errors to the upstream of the OTUk-level and to introduce the IAE. The length is four bits. It is located in the most significant four bits of the third byte of the

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SM overhead. In the IAE status, the field is set to 1011. The bit error number and non IAE state is omitted, insert the bit error number (0-8). Other six values may be caused by some irrelevant status. It should be explained as 0 bit error and BIAE inactivation. 

The backward defect indication (BDI) is used for OTUk-level to return the signal invalidity status detected in the terminal sink function. The length is one bit. It is located in Bit5 of byte3 of the SM overhead. When the BDI is set to 1, it indicates OTUk backward defect. Otherwise, it is set to 0.

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The Incoming Alignment Error (IAE) is used for the OTUk-level S-CMEP at the ingress point

to notify the peer S-CMEP at the egress point that the alignment error is detected in the introduction signals. The S-CMEP egress point can use this information to stress the bit error number. These bit error may be caused by the ODUk frame phase change at the TC ingress point. The IAE length is one bit. It is located in bit6 of byte 3 of the SM overhead. The IAE bit is set to 1 to indicate the frame alignment error. Otherwise, it is set to 0.



The last two bits of the SM is reserved, and is set to “00”.



S-Connection Monitoring End Point (CMEP): Section-Connection monitoring end-points represent end points of trails and correspond as such with the trail termination functions.


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OTN Principle

P-36

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General Communication Channel 0 (GCC0) is used to support the general communication between OTUk terminals. The length is two bytes. It is located in Column 11 to Column 12 of line 1. The GCC0 is the transparent channel. The format specification is not discussed here in this course.



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Then, it is the 2-byte OTUk reserved overhead, for the international standardization. It is located in column 13-column 14 of line 1. The reserved overhead is set to all zeroes.

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OTN Principle

P-37

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

The PM is similar to the SM.



The PM overhead is composed of three bytes. It is located in column 10-column 12 of line 3. The PM is composed of 1-byte TTI, 1-byte BIP-8, 4-bit BDI, 1-bit BEI, and 3-bit STAT.

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The definitions of TTI / BIP-8 / BEI / BDI are similar to those in SM. These parts support the channel monitor. 

The PM overhead does not support IAE and BIAE function. In addition, BIP-8 of the PM overhead is parity of the whole OPUk frame (column 15- 3824). But, the parity position is in the PM overhead, which differs from the BIP regenerated node in the BIP8.The BEI field needs not to support the BIAE function. Therefore, one value is less that of the SM overhead to indicate the return of the IAE state. Four bits of BEI fields in the PM overhead have nine effective values in total. 0-8 indicates 0-8 bit errors respectively. The other seven

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values are caused by some irrelevant status, which can be interpreted as 0 bit error.

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OTN Principle

P-38

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

The STAT field is used for the maintenance signals of ODUk channel level. The length is 3 bits. It is located in the least significant 3 bits of Column 12 of Line 3.



The table describes the meaning of the STAT field.

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OTN Principle

P-39

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The ODUk overhead defines TCM1-TCM6 of six domains. The Tandem Connection Monitoring (TCM) overhead supports the monitoring of the ODUk connection. It is used to the scenarios such as one or more optical UNI to UNI, NNI to NNI serial line connection

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monitoring, linear and ring protection switch sub-layer monitoring, the fault location of the optical channel serial line connection, and the service delivery quality acceptance. TCM6TCM1 are located in Column 5-Column 13 of line 2, Column 1-Column 9 of Line 3. Its format is similar to the SM of the OTUk overhead and the PM of the ODUk overhead. 

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TTIi / BIP-8i / BEIi / BIAEi / BDIi support the TCMi sub-layer monitoring, where, i ranges from 1 to 6. The definitions and functions of these parts are the same as the corresponding parts in SM. But, only the monitoring levels are different.

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STAT is used for the maintenance signal of TCMi sub layer, whether the IAE error exists in the source TC-CMEP, whether the source TC-CMEP is activated. The length is 3 bits. It is located in the least significant 3 bits of the TCMi field.



It indicates the meaning of the STAT field.



TCMi overhead has more BIAE function than PM overhead. In the maintenance signals in

s e c r u o s e R

the STAT field, there are more two meanings: No source TC, and TC in use but with IAE error.

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Along one ODUk trail, the monitored connections range from 0 to 6. The monitored multilevel connections can be overlay, nesting, or cascading. At present, the overlay mode is applicable to the test only. Each TC-CMEP inserts or extracts the TCM overhead from six

s e c r u o s e R

TCMi overhead domains. The corresponding network operator, network management system or switching control platform provides the TCMi overhead domain contents. 

As shown in the figure, the monitored connects A1-A2, B1-B2, and C1-C2 are nested, A1A2 and B3-B4 are nested, B1-B2 and B3-B4 are cascaded.

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As shown in the figure, the monitored connects B1-B2 and C1-C2 are overlaid, A1-A2 and B1-B2 are nested, A1-A2 and C1-C2 are nested.

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GCC1 and GCC2 can be used to access to the ODUk frame structure (that is, located in 3R regeneration points) between any two NEs. The length is 2 bytes, respectively located in Column 1-2 and Column 3-4 of Line 1. It is the transparent channel. Its function is similar

s e c r u o s e R

to OTUk overhead GCC0. The ESC function can be applied to the product.

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TCM Activation/Deactivation (TCMACT) overhead is 1-byte long, and is located in Column 4 of Line 2. Its definition is not determined yet.



Automatic Protection Switching (APS)/Protection Communication Control (PCC) overhead is

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applicable to the protection protocol communication, with the length of four bytes. This field can appear in up to 8-level nested APS/PCC signals. It can be used by multiple protection mechanisms. In the multi-frame, the first eight basic frames (for MFAS, it is 0-7) APS/PCC are sequentially allocated to ODUk channel layer, ODUk TCM1-TCM6 sub layers, and OTUk section layer. 

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The ODUk overhead defines 2-byte EXP, which allows the equipment supplier or network operator to use the extra ODUk overhead on the subnet. The specific function of the EXP is not limited to the standard, which is not defined within G.709 range.

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The ODUk overhead is allocated with one byte to transmit total 256-byte Fault Type & Fault Location (FTFL). The FTFL message is composed of forward area and backward area, with 128 bytes in each area, respectively containing the forward and backward fault type, operator identifier, and operator designated domain.


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The OPUk overhead defines 1-byte payload structure identifier (PSI) overhead to transmit the 256-byte PSI to indicate the OPUk signal type. The PSI overhead is in Column 15 of Line 4. The 256-byte PSI signal aligns with the ODUk multi-frame. PSI[0] is a 1-byte

s e c r u o s e R

payload type (PT); PSI[1]-PSI[255] are used for the mapping and cascading; PSI[1] is reserved, and PSI[2]-PSI[17] is the multiplex structure identifier (MSI). The MSI includes the ODU type and transmitted ODU tributary port number information. For OPU2, there are only four ODU1 tributary port number. Therefore, only four bytes PSI[2]-PSI[5] are needed, and the last 12 bytes of the MSI are set to 0.

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The OOS is the non-associated overhead, which is transmitted through the OSC. The optical layer overhead function should comply with the standard. The recommendation defines overheads and corresponding functions contained in the optical layer, and does

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not define the frame rate or frame structure. The optical layer overhead include OTS, OMS, OCh overheads, and generic management information overhead defined by the supplier, where, 

The OTS overhead is used to support the maintenance and operation function of the optical transmission section, and is terminated at the OTM signal assembly and dissemble places, including:

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

TTI: Transmit the TTI consisting of 64-byte character string. The TTI includes the source access point indication, destination access point indication, and information

designated by the operator.







BDI-P: Transmit the OTSn payload signal invalidity status detected from the OTSn terminal sink function to the upstream. BDI-O: Transmit the OTSn overhead signal invalidity status detected from the OTSn terminal sink function to the upstream. PMI: It is used to transmit the status of payload that is not added at the upstream of the OTS signal source terminal to the downstream, to suppress subsequent reporting of loss of signal.



To be continued in the next page


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

List the maintenance signals type;



Describe the function and application of maintenance signals.

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OTS, OMS, OCh are all optical layer trails and OTUk, ODUk, Client are all electrical layer trails.



OSC trail is independent, which is related to supervisory signal.



OTUK use SM section to send maintenance signals.



ODUK use PM and TCM to send maintenance signals.



OTS,OMS,OCh ,OSC send different optical layer maintenance signals.

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OCh client trail sets the source/sink port at the client side of OTU. LQG, as an example, it is GE service trail of the client port.



OCh trail sets the source/sink port at the WDM side of OTU. LQG, as an example, it is the wavelength trail.



s e c r u o s e R

OMS trail sets the source/sink port at the OUT/IN port of MUX/DeMUX. It is a trail of the multiplex signal.



OTS trail is the fiber connection between adjacent OM/OD/OA in the main path.



OSC trail is independent, which is related to supervisory signals.

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The FDI is the signal sent to the downstream in OMS and OCh layers, to indicate the detected upstream defects. FDI-P indicates the payload forward defect, and FDI-O indicates the overhead forward defect.

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OMS-FDI-P indicates the OMS servcie layer dfect of the OTS network layer.



OMS-FDI-O indicates that the transmission of the OMS overhead transmitted through the

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OOS is interrupted owing to the signal invalidity status of the OOS. 

OCh-FDI-P indicates the OCh service layer defect in the OMS network layer. When the OTUk is terminated, OCh-FDI-P serves as the ODUk-AIS signal to continue.



OCh-FDI-O indicates that the transmission of the OCh overhead transmitted through the OOS is interrupted owing to the signal invalidity status of the OOS.

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The FDI signal is generated in the adaptation sink function. In the trail terminal sink function, it is generated to suppress the downstream defects and invalidities detected owing to the transmission interruption of the upstream signals. The FDI is similar to AIS. When the signal is in the optical domain, use the FDI. When the signal is in the digital domain, use the AIS. The FDI served as the non-associated overhead is transmitted in the OTM overhead signal (OOS)


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AIS is the electrical layer OTUk, ODUkP, ODUkT, and customer layer CBR sent to downstream to indicate the detected upstream defect, to suppress the downstream defects and invalidities detected due to the interruption of upstream signal transmission.

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The AIS of ODUkP and ODUkT layer uses the ASI with all-1 pattern. 

Note: 

OTUk-AIS supports the new service layer in future. At present, only the signal is required to be detected, instead of the generation of this signal. According to this recommendation, Huawei equipment only supports the detection of the OTUk-AIS, instead of inserting OTUk_AIS. CBR AIS is generated in the the ODUk/CBRx adaptation sink function. If the SDH receives this signal, it is detected as the LOF.

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The AIS of ODUkP and ODUkT level uses the all-1 pattern, as shown in the figure.



When we introduce the PM and TCMi overhead, we have learnt that the value 111 of STAT field of PM or TCMi indicates the detected ODUk_AIS signals. When ODUkP or

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ODUkT detects the AIS, it only concerns about the value of the STAT of the corresponding level. For example, to detect the AIS of the TCM1, check whether the STAT corresponding bit of the TCM1 is 111; To check the AIS of the PM, check whether the STAT corresponding bit of the PM is 111. 

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To insert the AIS, the ODUkP or ODUkT is not distinguished. For either of them, insert to PM or 6-level PCM overhead area or all payloads (excluding FTFL byte). Therefore, it is called the insertion of ODUk-AIS signals. The ODUk_AIS may be generated in the adaptation sink function from OTU to ODU or in the ODUkT termination sink function. For

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the adaptation sink function from OTU to ODT, insert the ODUk_AIS owing to the invalidity of the service layer. For the ODUkT termination sink function, when the TCM is in the operation mode, insert ODUk_AIS owing to the detection of the LCK, OCI, and TIM. Whether the TIM is inserted with the AIS can be set.



When the AIS is cleared, 111 of the STAT of the local area is cleared also. For example, for the TCM1 source function, change the STAT of the TCM1 from 111 to 001.

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The Backward Defect Indication (BDI) includes the OTS of the optical layer, the BDI of the OMS layer, OTUk and ODUkP of the electrical layer, and the BDI of the ODUkT layer.

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The BDI-P indicates the payload backward defect. The BDI-O indicates the overhead

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backward defect. If the remote defect of the BDI inserting the OOS detected consecutively in X ms, the BDI is generated. If the BDI-P upstream defect inserted by OOS detected within the consecutive Y ms is cleared, clear the BDI-P. The values of X and Y needs the further study. 

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For the electrical layer OTUk, ODUkP and ODUkT layer’s BDI, we have learnt the electrical layer overhead part. If the BDI bit of the SM/PM/TCMi overhead domain of the consecutive five frames (bit 5 of byte 3) is 1, generate the dBDI. If the BDI bit of the SM/PM/TCMi overhead domain of the consecutive five frames (bit 5 of byte 3) is 0, clear the dBDI.

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If the signal is invalid, the BDI should be cleared.

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The Open connection indication (OCI) is used for the optical layer OCh, electrical layer ODUkP, and ODUkT to indicate that the upstream signal does not connect to the trail terminal source signals. The OCI signal is generated in the connection function. Through

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the connection function, output at any output connection point that is not connected to any input connection point. The OCI signals are detected in the trail terminal sink function. 



For the OCh layer, if the input and output is detected in the consecutive X ms, generate the OCI. If the input and output connection is normal or the overhead signal is invalid in the consecutive Y ms, clear OCI. The values of X and Y are still under the research.

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As shown in the figure, it is the OCI pattern of the ODUkP and ODUkT layer. Detect the OCI, which is similar to the detection of the AIS. Check whether the corresponding bit of the STAT is 110. For example, check the OCI of the TCM1 to check whether the STAT

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corresponding bit of the TCM1 is 110. Detect the OCI of the PM, to check whether the STAT corresponding bit of the PM is 110. Insert the OCI, and insert to PM and 6-level TCM area and all payloads. Clear the OCI to clear 110 of this area STAT. For example, for TCM1, it means to change the STAT of the TCM1 from 110 to 001. If the data signal is invalid, the OCI should be cleared.


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

To support the operator's requirement of locking the user access point signal, ODUkP and PDUkT layer provide the LCK maintenance signals to indicate the upstream connection is the locked signal, without signals passing.



When the operator performs sets up the test, the customer signals are replaced by the locked (LCK) fixed digital signals. It is generated through the service layer adaptation sink

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and source function, and is sent to the downstream. The downstream termination sink function allows the report of the LCK alarm, indicating that the upstream connection is locked and no signals pass. 

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As shown in the figure, it is the LCK pattern of the ODUkP and ODUkT layer. Detect the LCK, and check whether the corresponding bit of the STAT is 101. For example, check the LCK of the TCM1 to check whether the STAT corresponding bit of the TCM1 is 101. Detect

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the LCK of the PM, to check whether the STAT corresponding bit of the PM is 101.

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Insert the LCK, and insert to PM and 6-level TCM area and all payloads. Clear the LCK to clear 101 of this area STAT. For example, for TCM1 source function, change the STAT of the TCM1 from 101 to 001.



The priority of inserting the LCK is higher than that of the AIS. That is, if a user sets the insertion of the LCK and meets the condition of automatic insertion of the ASI, the result is insertion of the LCK.


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Incoming Alignment Error (IAE) and Backward Incoming Alignment Error (BIAE). The electrical layer OTUk and ODUkT provide the maintenance signals of IAE and BIAE. IAE and BIAE are not the fault reasons. The IAE is used to suppress the near end performance of

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the OTUk and ODUkT (EBC and DS). The BIAE is used to suppress the remote performance of the OTUk and ODUkT. 

For the IAE of the OTUk, if the IAE bit in the consecutive 5-frame SM overhead domain (bit 6 of byte 3) is 1, generate the dIAE. If the IAE bit in the consecutive 5-frame SM overhead domain (bit 6 of byte 3) is 0, clear the dIAE. For the IAE of the ODUkT, if the received STAT information is 010, generate the dIAE. If the received STAT information is not 010, clear the dIAE.

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If the signal is invalid, the dIAE and dBIAE should be cleared.

For the signals sent to the upstream by the BIAE, if the BEI/BIAE bit of the consecutive 3frame SM/TCMi overhead domain (bit1-bit4 of byte 3) is 1011, generate dBIAE. If the BEI/BIAE bit of the consecutive 3-frame SM/TCMi overhead domain (bit1-bit4 of byte 3) is 1011, clear dBIAE.


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For the framing and monitoring, the OTUk and ODUkP support to obtaining the LOF and LOM through the detection of the FAS and MFAS. The ODUkP is applicable to the scenario from the low-level ODU multiplexing to the high-level ODU signals.



For the continuity monitoring, three layers support the TTI signals of the corresponding level.



For the information maintenance, three layers support AIS, BDI, and BEI signals. The ASI of the OTUk layer is the generic AIS signal. In ODUkP and ODUkT, there are all-1 AIS signals.



ODUkP and ODUkT layers support OCI and LCK signals.

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The ODUkT layer supports the LTC signals. Note: LTC indicates there is no TCM source.

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OTUk and ODUkT support the IAE/BIAE signals.

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For the monitoring of the signal quality, three layers support the performance detection based on the BIP-8 calculation. That is, check the OPUk frames. But the check location and layers are different.


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Classify the alarms into the corresponding layer;

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Outline the suppression mechanism of alarms.

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Firstly,about the OTN alarm of each electrical layer, for the alarms of OTUk layer, except the BEFFEC_EXC alarm related to the FEC, other alarm names start with “OTUk”. For the ODUkP layer, except ODUk_LOFLOM, other alarms start with “ODUk_PM”. For ODUkT

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layer alarms, the name starts with “ODUk_TCMi”. The OPUk layer alarm starts with “OPUk”.

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This table lists OTN performance events in the OTUk, ODUk_PM, and ODUk_TCMi layers. For definitions related to the performances, see ITU-T G.8201.



far end ES. 

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ES: Errored Second: When one or more bit error blocks are found in one second, it is called ES. FEES: SES: Severely Errored Second: In one second period, include ≥ 15% bit error blocks, or, there is at least one defect (OCI/AIS/LCK/IAE/LTC/TIM/PLM). FESES: far end severely errored second.



SESR: Severely Eroded Second Ratio: It indicates the ratio between the SES and total seconds in the

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available time within the fixed test interval. FESESR: far end Severely Eroded Second Ratio. 

BBE: Background Block Error: It indicates the bit error block beyond the severely eroded second.

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FEBBE: far end background block error.

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BBER: Background block error ratio. It indicates the ratio between the BBE and total blocks in the available time within the fixed test interval. The total number of the blocks excludes the number of the blocks in the SES. FEBBER: far end background block error ratio. UAS: Unavailable second: It starts from 10 consecutive SES events. The 10 seconds are considered as a part of the unavailable second. The new available time period starts from 10 consecutive nonSES events. Ten seconds can be considered as one part of the available time. FEUAS: Far end unavailable second.



IAES: Incoming Alignment Error Second: When the IAE error exists in one second, the second is the incoming alignment error second. BIAES: backward Incoming Alignment Error Second.



After the FEC is used, the definitions of all performance events are after the FEC. That is, the detection of the performance event (for example, BBE and SES) is after all error corrections.


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Which kinds of the components does the OTM-n.m have? 

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OTSn, OMSn, OCh, OTUk/OTUkV, ODUk, OPUk

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What’s the difference between SM and PM? 

SM is in the OTUk OH,PM is in the ODUk OH.



SM contains TTI/BIP-8/BEI/BIAE/BDI/IAE/RES,PM contains TTI/BIP-8/BEI/BDI/STAT.

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LAN Introduction……………………………………………………………………Page 4

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Ethernet Principles…………………………………………………………….……Page10 Ethernet Port Technology…………………………………………………….……Page29 EoS Introduction…………………………………………………………………..Page39 VLAN Basics and Port Attributes………………………………………….……….Page57

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QoS Introduction and Application……………………………………….………. Page76

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A network is a complex system interconnected formed by interconnected people or things. Networks exist everywhere in our life, for example, the telephony network and telegraph network. There are also many network systems in one's body, for example, the nerve

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system and the digestive system.



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The computer network is a large-scale and powerful system that connects computers and peripheral devices in different areas through communication lines. In the computer network, substantive computers can exchange information and share information resources. The computer network was developed to meet the requirement for exchanging information and sharing information resources.

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In the initial stage of the computer network, each computer is an independent device. Computers work independently and do not communicate with each another. Combination of the computing technology and communication technology brings a far-reaching influence to the organization of the computer system and makes possible the communication among computers. Computers of different types use the same protocol to communicate, and thus the computer network comes into being.


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The Internet is a large network formed by networks and devices. Based on the covered geographic scope, networks are classified into LAN, WAN, and



Metropolitan Area Network (MAN) whose size is between the LAN and WAN.



Local Area Network (LAN) 

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A LAN is formed by connected communication devices in a small area. A LAN covers a room, a building, or an industry garden. A LAN covers several kilometers. It is a combination of computers, printers, modems, and other devices interconnected through various mediums within several kilometers.

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Wide Area Network (WAN)

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A WAN covers a larger geographic scope, such as a state or a continent. It provides the data communication service in a large area and is used to connect LANs. The China Packet Network (CHINAPAC), China Data Digital Network (CHINADDN), China Education and Research network (CERnet), CHINANET, and China Next Generation Internet (CNGI) are all WANs. A WAN connects LANs that are far from each other.


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LAN is a network that connect all kinds of communication devices together, within a room, building or garden. The distance is usually only several miles. It has features such as short distance, low delay, high rate and reliability and so on.

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Standard is a set of rules or program that are widely used or defined by organization. It defines the protocols, and performance set. IEEE 802.X is the most common used standard.

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In China, the common local network is Ethernet, ATM (Asynchronous Transfer Mode). They are different in topology, transmission medium, signal rate, frame structure, and so on. Ethernet is widely used because it’s the most economical one and it develops very quickly.

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Common devices used in LAN：

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Cable：Enlarging the transmission distance, e.g. fiber, twisted pair, coax and so on。

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NIC，Network Interface Card: Seated in the main board of the computer，converting the

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user data into special forms that other network devices can read. 

HUB is a multiple ports device. When one of the cable is broken, others will not be affected.

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Switch is also a multiple ports device. Every two ports have private service bus, so switch has a higher ability to forward the signals.

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Router is an important device that can connect LAN, WAN and Internet together. The router can analyze route information and choose a best route for packets, and forwards them in order.

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ATM is a special switching device used in ATM network. It is only applied in back-bone network because of its special techniques.


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Carrier Sense Multiple Access / Collision Detect (CSMA/CD) is an effective method for multi-point communication under the condition of medium sharing.

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1) If the medium is idle, the transmission will be made; otherwise, it goes to step 2. 2) If the medium is busy, the channel will be monitored till it is idle and the transmission will be made at once. 3) If collision is detected during the transmission, a short and small jamming signal will be sent to let all the stations know that conflict occurs and stop the transmission.

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4) After sending the jamming signal and waiting for a random time, the transmission will be tried again and it will go to step 1 to start again.

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The CSMA/CD technology adopted by the Ethernet may reduce the waste of the channel caused by the conflict to the minimum extent. However, it cannot ensure the transmission

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efficiency in case of high network load.

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As limited by the CSMA/CD algorithm, an Ethernet frame cannot be shorter than 64 bytes, which is determined by the maximum transmission distance and the mechanism of collision detection.

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The limitation of the frame length can prevent the situation that a station finishes sending the last bit; however, the first bit does not reach the remote destination. The remote

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station believes the line is idle and continues to send data. The conflict, therefore, occurs. 

The upper layer must guarantee that the Data field contains a minimum of 46 bytes. If the Data field is shorter than 46 bytes, the upper layer must fill the filed. The 46-byte Data field, 14-byte Ethernet header, and 4-byte check code consist of a 64-byte frame, which is a frame of minimum length.

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The maximum length of the Data field is 1500 bytes.

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The maximum transmission distance is determined by factors such as line quality and signal attenuation.

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MAC: media access control 

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The MAC address is the physical address of each device connected to the network. MAC address assignments are administrated by IEEE and are be globally unique.

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Each address is composed of two parts, the OUI which is the Organization Unique Identifier which is the address space assigned to the provider, the remainder of the address space is assigned by each organization. 

The first 24 bits denotes the provider code and the last 24 bit is assigned at the provider’s discretion.

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MAC address includes 48 bits and it is shown as 12 dotted hexadecimal notations MAC address is exclusive globally which is allotted and managed by IEEE. Every MAC address is composed of two parts. The first 24 bits part is the vendor code

and the other 24 bits part is serial number

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All 1’s in the address otherwise written as FF-FF-FF-FF-FF-FF in hexadecimal denotes a broadcast address, which will be read by all attached stations.

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If 48 bits are all “1”, it means the address is used for broadcast

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If the 8th bit is “1”, it means the address is used for multicast

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The destination address in the Ethernet header can be one of three forms: 

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Unicast address: Only the specified host will process the frame e.g. a frame sent from PC to Server

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Broadcast address: This frame will be processed by every host (PC, Printer, server, etc) Multicast address: All hosts that are members of the specified multicast group will process this frame e.g. a router to other routers

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Preamble: 7 bytes of 10101010 to allow timing synchronisation between sender and receiver

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SFD: Start Frame Delimiter 10101011 to tell the receiver the next byte is the start of the frame DMAC: destination MAC address, 6bytes

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SMAC: source MAC address, 6bytes

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Length/Type: 2bytes, it has the following meanings:

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Ethernet Frame Fields

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if Length/Type > 1500 ,this field indicates the type of the upper protocol of an Ethernet_II frame

if Length/Type <=1500, the field indicates the length of the data, and it is a 802.3 frame.

DATA: 46~1500bytes , If the data field is less than 46 bytes padding is used to fill up the frame to make sure that the length of frame must be at least 64 bytes. FCS: Frame check sequence 4bytes

The whole length of the fame is 64~1518 bytes.


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From 10M Ethernet, the rate of Ethernet increases of 10 times.

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Currently FE/GE are the most common ones, in the coming future more and more NNI (Network Node Interface) will be upgrade to 10GE in Metro Ethernet network.

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Generally, 10Mbit/s Ethernet is only positioned at the access layer of the network. The new generation products of multimedia, video and database can easily overwhelm the Ethernet running at the rate of 10Mbit/s.

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The 10Mbit/s Ethernet can achieve the connection of 100m in distance.

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Ethernet networks providing 10 Mbps of bandwidth seemed very fast when it was first released, but developments in computer speed meant that by the early 1990’s computers were running faster and could provide a heavy load for a 10 Mbps network. The network

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became a bottleneck slowing down communications and business then it became clear that a faster speed technology would need to be developed. 

The development of fast Ethernet began in 1993 and became a standard in 1995. The foundations remained the same as for those for 10BASE-T: Ethernet frame format, multiport repeaters, bridges and structured wiring but with ten times the transmission speed. Some trade offs were required however. The telephone cable used would not support the transmission frequencies of fast Ethernet. Telephone quality cable has too much signal degradation for fast Ethernet and the level of electromagnetic radiation

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The 100BaseTX portion of the standards documents fast Ethernet over standard category 5 UTP. This is the dominant form of Fast Ethernet and has become the standard Ethernet installation.

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In the 100Base FX option, the F relates to operation over fiber optic cabling. Greater

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allowed by the FCC and European regulatory bodies is exceeded during transmission. So either a different form of cable was required or a different method of using the same form.

distances can be achieved with fiber. 100BASE-FX used in half duplex mode on a point to point link can achieve a distance of 412 meters, but this is limited due to the collision domain requirements. In full duplex mode distances of 2000 meters can be reached.


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The category 3 UTP scheme, called 100Base-T4, uses a signaling speed of 25 MHz, only 25 percent faster than standard Ethernet's 20 MHz. However, to achieve the necessary bandwidth, 100Base-T4 requires four twisted pairs.

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For category 5 wiring, the design, 100Base-TX, is simpler because the wires can handle clock rates of 125 MHz. Only two twisted pairs per station are used, one to the hub and

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one from it. 100Base-TX and 100Base-T4 are collectively referred to as 100Base-T. 

The last option, 100Base-FX, uses two strands of multimode fiber, one for each direction, so it, too, is full duplex with 100 Mbps in each direction. In addition, the distance between a station and the hub can be up to 2 km.

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The IEEE Gigabit Ethernet task force is responsible for standards development for this technology. The Gigabit standard was developed as the IEEE 802.3z supplement and the work assisted by the Gigabit Ethernet Alliance, which is a group of major product manufacturers that are assisting the task force with their development project.

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Like Fast Ethernet, this system uses an upgraded physical layer protocol and an upgraded MAC layer which is similar to both the 10Mbps and 100Mbps standards. There are however some differences to do with collision domain parameters to enable Ethernet to work at these speeds.

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Gigabit Ethernet can operate in both half and full duplex modes and has become increasing popular in both backbone, campus and general device connectivity as equipment prices fall.

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Although the standard for Gigabit Ethernet offers several changes to the traditional 10Mbps variant it is viewed as a natural extension to the technology. Products that combine Gigabit Ethernet , Fast Ethernet and 10Mbps Ethernet are readily available allowing for a seamless integration of the technology.

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The specification includes the following media types: 

1000BaseLX - Single mode fiber (3km plus)

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1000BaseSX - Multi-mode fiber (300 - 550 meters)

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1000BaseCX - Coaxial cable (25 meters plus)

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1000BaseT - UTP (multi-pair up to 100m)

Gigabit Ethernet is ideal for LAN backbone solutions. It scales well from existing Ethernet as the speed is the major technological change and the technology is obviously already widely utilized and understood.


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Gigabit Ethernet supports two different modes of operation: full-duplex mode and halfduplex mode. The ''normal'' mode is full-duplex mode, which allows traffic in both directions at the same time.

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Gigabit Ethernet supports both copper and fiber cabling.

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LAN PHY  The most common variety is referred to as LAN PHY, used for connecting between routers and switches. Although called LAN, this can be used with 10GBase-LR and ER up to 80 km. LAN PHY uses a line rate of 10.3 Gbit/s and a 64B/66B encoding.  10GBASE-SR (short range) has a range of 26 m to 82 m depending on multi-mode fiber cable type.  10GBASE-LRM, also known as 802.3aq, supports up to 220 m on FDDI-grade 62.5 µm multi-mode cable  10GBASE-LR is a Long Range technology over 1300 nm single-mode fiber between 10 Km to 25 Km.  10GBASE-ER (extended range) supports distances up to 40 km over single-mode fiber (using 1550 nm).  10GBASE-LX4 uses coarse wavelength division multiplexing to support ranges of between 240 m and 300 m over deployed multi-mode cabling. This is achieved through the use of four separate laser sources operating at 3.125 Gbit/s in the range of 1300nm on unique wavelengths. This standard also supports 10 km over single-mode fiber.  10GBASE-T, or IEEE 802.3an-2006, provides 10 gigabit/second connections over conventional unshielded or shielded twisted pair cables. 10GBASE-T works over shorter distances with Category 6 cabling (up to about 56 meters), with the possibility of up to 100 meters for new cable installations designed for 10GBase-T. The 802.3an standard defines the wire-level modulation for 10GBASE-T as a Tomlinson-Harashima Precoded (THP) version of pulse-amplitude modulation with 16 discrete levels (PAM-16), encoded in a two-dimensional checkerboard pattern known as DSQ128. The mathematics for this are 3.125bits encoded per symbol x 833Mbauds x 4 pairs = ~10Gbps.

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10GE Ethernet service, data rate is 10.31Gbit/s.

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Connect with 10GE Ethernet service.

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10GBase-SW/LW/EW WAN Interface

mapping of Ethernet frames into simplified SONET/SDH frames, data rate is 9.953 Gbit/s.

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Connect with 10G POS service.

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10GBase-SR/LR/ER WAN Interface

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10.3 Gbit/s for the serial (LAN).

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The half-duplex mode has the following features: 

Receiving data or sending data takes place only in one direction at a time.

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CSMA/CD is used.

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This mode has the limitation to the transmission distance.

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The full-duplex mode has the following features: 

Receiving data and sending data can take place simultaneously.

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The maximum throughput is double the transmission rate.

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This mode does not have the limitation to the transmission distance.

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Auto-negotiation was originally defined in the IEEE 802.3u standard in 1995. It was introduced into the fast Ethernet part of the standard but is also backwards compatible to 10BASE-T. This was later updated in 1999, the negotiation protocol was significantly

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extended by IEEE 802.3ab, which specified the protocol for Gigabit Ethernet, making autonegotiation mandatory for Gigabit Ethernet. 

Auto-negotiation is used by devices that are capable of different transmission rates (such as 10Mbit/sec and 100Mbit/sec), and different duplex modes (half duplex and full duplex). Every device will declare its possible modes of operation. The two devices then choose the best possible mode of operation that are shared by the two devices, where higher speed (100Mbit/sec) is preferred over lower speed (10Mbit/sec), and full duplex is preferred over half duplex at the same speed.

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Parallel detection is used when a device that is capable of auto-negotiation is connected to one that is not. This happens if one device does not support auto-negotiation or it is disabled via software. In this condition, the device that is capable of auto-negotiation can determine the speed of the other device. This procedure cannot determine the presence of full duplex, so half duplex is always assumed.


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A duplex mismatch will result if the other device is in full duplex mode, that is, one device is using full duplex while the other one is using half duplex. The typical effect of duplex mismatch is that the connection is working but at a very low speed.

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Many newer Ethernet NICs, switches and hubs automatically apply an internal crossover when necessary. This feature is known Auto-MDI/MDI-X, Universal Cable Recognition or Auto Sensing. This eliminates the need for crossover cables, uplink ports and manual

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selector switches found on many older hubs and switches. This also reduces installation errors. 

Crossover cables for 10/100 Ethernet have only pairs 2 and 3 swapped, a 1000BASE-T crossover cable also has pairs 1 and 4 swapped.

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The Ethernet standard includes an optional flow control operation known as "PAUSE" frames. PAUSE frames permit one end station to temporarily stop all traffic from the other end station.

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For example, if we have a full-duplex link that connects two devices called “Device A" and “Device B". If Device A transmits frames at a faster rate than Device B can process because

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there is no buffer space remaining to receive additional frames. Device B can transmit a PAUSE frame to Device A requesting that Device A stop transmitting frames for a specified period of time. 

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The format of a PAUSE frame conforms to the standard Ethernet frame format but includes a unique type field with additional parameters.

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The MAC Control Parameters field contains a 16-bit value that specifies the duration of the

PAUSE in units of 512-bit times. Valid values are 00-00 to FF-FF (hex). A 42-byte reserved field (transmitted as all zeros) is required to pad the length of the PAUSE frame to the minimum Ethernet frame size.


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When the data processing/transferring capability of the equipment fails to handle the flow received at the port, congestion occurs on the line. To reduce the number of discarded packets due to buffer overflowing, proper flow control measures must be taken.

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The half-duplex Ethernet port applies the back-pressure mechanism to control the flow. Currently, the half-duplex Ethernet function is not widely applied.

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Concatenation, which is one of the important SDH transmission features, specifies how to transmit service signals whose rate is greater than C-4 (149 760 kbit/s). The concatenation technology does not impair service signals.

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Concatenation is a process for combining multiple containers as one container that maintains the integrity of the bit sequences.

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Concatenation service transmission is based on ITU-T Recommendation G.707.

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Contiguous concatenation concatenates the contiguous C-4s in the same STM-N into an entire structure (C-n-Xc) to be transported. VC-4-Xc in contiguous concatenation has only one column of POH indication. Therefore, contiguous concatenation maintains the

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contiguous bandwidth throughout the whole transmission process. Contiguous concatenation requires the support of all the equipment that services travel by. Most existing equipment, however, does not have such capabilities.

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Virtual concatenation concatenates VC-n containers in different STM-Ns, which can be transferred in the same route or different routes, into a big virtual structure (VC-n-Xv) to transport. In virtual concatenation, each VC-n has a separate structure and POH to form a

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complete VC-n structure. Multiple concatenated VC-ns functions interleaving of several VCns. The equipment on both the source NE and sink NE requires only special hardware for concatenation.

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The concatenation indicator in the AU-4 pointer specifies that multiple C-4 payloads carried in a VC-4-Xc must remain together. The available capacity for mapping equals the C-4 capacity of multiple C-4s multiplied by X (for example, when the value of X is 4, the

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capacity is 599040 kbit/s; when the value of X is 16, the capacity is 2396160 kbit/s). 

Columns 2 to X of VC-4-Xc are the fixed stuffed bits, and column 1 of VC-4-Xc is used as the POH, which is allocated to the VC-4-Xc.

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The first AU-4 of AU-4-Xc must have a pointer value within the specified range. For all the subsequent AU-4s of AU-4-Xc, their pointers must be set to concatenation indication. That is, bits 1 to 4 are set to "1001", bits 5 to 6 are not specified, and bits 7 to 16 are set to ten 1s. Concatenation indication specifies that the pointer processor performs the same operations as the first AU-4 of AU-4-Xc.

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One VC-4-Xv provides the contiguous payload area (C-4-Xc) whose payload capacity is C-4 multiplied by X. The container can be mapped into X individual VC-4s, which form the VC4-Xv. Each VC-4 has its POH, which is the same as the POH in a common VC-4. The H4

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byte in POH is used as the sequence number specified in the virtual concatenation and multi-frame indicator. 

The MFI signal, which is generated in all VC-4s of VC-4-Xv, is transmitted through bits 5-8 in the H4 byte of all the VC-4s. The MFIs are numbered from 0 to 15.

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According to the requirements of SDH contiguous concatenation services, all the NEs through which the end-to-end services travel must be capable of processing VC-4-Xc services. The network conditions, however, are difficult to meet. Therefore, VC-4-Xc

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services are generally converted into VC-4-Xv services on the network boundary where contiguous concatenation services are received. In this case, the intermediate NEs on the network need to process VC-4 services but not VC-4-Xc services. The NEs on the network boundary convert VC-4-Xc services to VC-4-Xv services.

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The existing SDH service line board on the OptiX OSN 1500/2500/3500/7500/9500 can access and process contiguous concatenation services.

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Most EoS service data boards on the OptiX equipment form VC-TRUNKs in virtual concatenation mode, which facilitates flexible networking and supports multi-path

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transmission. The virtual concatenation technology can be used with the LCAS scheme for adjustment of link bandwidth.

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



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When a physical channel fails, all the concatenated channels fail. In other words, all services are interrupted. Severe impact of bandwidth adjustment on services: If you adjust the bandwidth after a service is created, the service is interrupted for certain period of time.

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Long service provisioning time: The duration from the time when a subscriber applies for a service to the time when the service is available lasts very long.

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Both contiguous concatenation and virtual concatenation have the following problems:



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// : p

Due to development of services transmitted on SDH/SONET networks and constantly increasing demands for access bandwidths, the previous fixed container (with the maximum granularity of VC4) no longer meets the relevant requirement. Therefore, the concatenation technology emerges. Compared with contiguous concatenation, virtual concatenation is more flexible and enjoys higher bandwidth utilization. 



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The LCAS is a supplement to the virtual concatenation technology. The LCAS supports the following functions: 





The LCAS dynamically adjusts (adds or deletes) the service bandwidth without affecting the availability of the existing services. If some physical channels fail in virtual concatenation, the LCAS suppresses these physical channels. Other physical channels in virtual concatenation can transfer services. Hence, this prevents a situation where the failure of a single physical channel causes interruption of services. The LCAS is applied on the basis of virtual concatenation and can improve the performance of virtual concatenation. The control packet is transported in the reserved SDH overhead byte (H4 byte for a higher order virtual concatenation, or K4 byte for lower order virtual concatenation). The LCAS can dynamically adjust the number of virtual containers for mapping required services to meet the bandwidth requirements of different services. As a result, the bandwidth utilization is improved.


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

The LCAS, which complies with ITU-T G.7042, is developed to solve the virtual concatenation problems.



In the LCAS scheme, the source NE and sink NE can dynamically adjust the required VCG

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capacity based on the traffic volume of the services to be mapped and the required bandwidth. When a link of the VC-TRUNK member where services are mapped is faulty, the LCAS can also cancel the link. As shown in the figure on page 15, in normal state, assume that 4xVC-4 virtual concatenation are mapped in VC-TRUNK. When two channels in the virtual concatenation fail, the LCAS automatically adjusts the VCG capacity. Although the service rate is decreased, the service data is protected. When the failed channels recover, the bandwidth of the virtual concatenation is automatically restored.

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On an MSP ring network, the transmission bandwidth of the protection MSP channel can

be fully utilized if the LCAS technology is adopted to dynamically adjust the virtual concatenation bandwidth. Specifically, the protection MSP channel transports extra services whose reliability is not assured because they are not protected. If virtual concatenation is adopted, some services are mapped into the working channel, and the other services are mapped into the protection channel. If the protection channel fails, the LCAS dynamically decreases the VCG members in a virtual concatenation group. As a result, the service transmission bandwidth automatically decreases, and the services are not interrupted. When the protection channel recovers, the service bandwidth is automatically restored.


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Synchronization of changes in the service traffic between the source NE and the sink NE is achieved by control packets. Each control packet describes the state of the link during the next control packet. In other words, the link state change information is sent in advance to

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facilitate the receiver to timely process or modify the relevant configuration. 

The LCAS is based on virtual concatenation. The control packet (K4 byte for lower order virtual concatenation) consists of consecutive 16 H4 bytes.



The CRC method for assurance of the control frame is used for the overhead in the control packet. When a control packet is received, the CRC method is used to immediately check the control packet and determine whether the contents are valid.



Definition (implementing method) of a control packet:

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or

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

In higher order (HO) mode: 16 frames form a multi-frame (note: 8000 frames are

transmitted each second). 



Consisting of H4 overhead byte: There are altogether consecutive 16 frames from frame 8 in multi-frame n (multi-frame 2) to frame 7 in multi-frame n+1. Bits 1-4 in the H4 byte of each frame have different meanings in different frames. For example, bits 1-4 in frames 0 and 1 represent the multi-frame number, and bits 1-4 in frames 8 and 9 represent the member status. For the interpretation and function of each field (for example, CTRL), see the subsequent definition and description of the overhead control field.


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Encapsulation format 

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MSTP defines three standard encapsulation formats: HDLC, LAPS, and GFP. Different vendors use different encapsulation formats. In practice, a vendor uses

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one or two formats. Although the same encapsulation format is used, certain differences also exist. 

The exchangeability of Ethernet encapsulation formats is important. If the encapsulation formats specified by different vendors are exchangeable, GE or FE services not only traverse an SDH network that consists of the equipment of different vendors, but also do not require the SDH equipment provided by the same vendor at both ends. The SDH network that consists of equipment of different vendors becomes a transparent channel of Ethernet service, and provides

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a basis for building wider Layer-2 networks.



The GFP format is highly standardized. It is used for mapping data services into SDH/OTN services and complies with ITU-T G.7041. The GFP format currently supports frame-mapped GFP and transparent GFP. It can perform statistical multiplexing for data signals to effectively prevent error frames caused by bit errors, therefore facilitating interconnection and interworking between the equipment of different vendors.


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Generic framing procedure (GFP), which is defined in ITU-T G.7041, can correct errors in data packet headers and multiplex channel identifiers on a port (it can combine multiple physical ports as a network path). The most important feature of GFP is that GFP supports

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frame mapping and transparent transmission, therefore supporting more applications. In frame mapping mode, the frames in framed data signals are encapsulated into GFP frames. Lower rates can be increased and multiplexed. In transparent transmission mode, data signals are received but are not changed. Digital encapsulation based on low overhead and low delay is performed for SDH frames. In principle, GFP can be used for encapsulating any protocol-compliant packets. It assures the packets in simple protocol format to be transmitted at the optical transmission layer. It also assures flexible encapsulation and smaller bandwidth granularities.

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P-49

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Generic framing procedure (GFP), which is defined in ITU-T G.7041, can correct errors in data packet headers and multiplex channel identifiers on a port (it can combine multiple physical ports as a network path). The most important feature of GFP is that GFP supports

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frame mapping and transparent transmission, therefore supporting more applications. In frame mapping mode, the frames in framed data signals are encapsulated into GFP frames. Lower rates can be increased and multiplexed. In transparent transmission mode, data signals are received but are not changed. Digital encapsulation based on low overhead and low delay is performed for SDH frames. In principle, GFP can be used for encapsulating any protocol-compliant packets. It assures the packets in simple protocol format to be transmitted at the optical transmission layer. It also assures flexible encapsulation and smaller bandwidth granularities.

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GFP supports the following working modes: 

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Frame-Mapped GFP (GFP-F), which is a PDU (such as IP and Ethernet) oriented processing mode, performs one-to-one mapping between the upper-layer PDUs of

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Ethernet MAC frames and the GFP PDUs. 

Transparent GFP (GFP-T), which is a data coding block (such as Fiber Channel and ESCON) oriented processing mode, transparently maps 8B/10B payload into GFP frames for low-delay transmission. The signals that can be transparently mapped include Fiber Channel signals, ESCON signals, FICON signals, and GE signals. In GFP-T mode, the entire frame need not be buffered. All the words in the signals are separately decoded, and are then mapped into fixed-length GFP frames, regardless of data words or control words. As a result, the 8B/10B control words in

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the signals are protected.

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P-51

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GFP core header 

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PDU length indicator (PLI)



PLI indicates the length of the GFP payload area. In a GFP client frame, the minimum value of PLI is 4. The values from 0 to 3 are used for GFP control frames.

GFP payload frame header 

The GFP payload frame header includes the PTI field and the Extension Header field.



Payload Type Identifier (PTI)



The PTI field indicates the type of the payload.





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The GFP core header consists of four bytes, including one 16-bit PDU length indicator field and one 16-bit core header error check (cHEC) field.

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

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Frame structure in GFP encapsulation format

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The GFP extension header, which is an extended field that contains 0 to 60 bytes, supports data link header such as virtual link identification, source/destination address, port number, class of service, and extension header error control.

Payload frame check sequence (FCS) field 

The CRC-0/16/32 sequence assures that the contents of the GFP payload information are correct.


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Encapsulating Ethernet MAC frames 

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The Ethernet MAC frames from the destination address through the frame check sequence, inclusive, are placed in the GFP-F payload field. The byte sequence and

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bit identification within a byte in a GFP-F frame remain unchanged. 

Deleting and restoring an inter-frame gap (IFG) 

When the Ethernet frames are not locally encapsulated in GFP-F format, their IFGs need to be deleted and restored based on the following rules:

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

The IFGs are deleted before GFP-F adaptation on the source NE, and are inserted after GFP-F deadaptation on the sink NE. When Ethernet MAC frames are extracted from the service data, the IFGs are deleted. After GFP-F adaptation is performed for the extracted Ethernet MAC frames on the source NE, the Ethernet MAC frames are encapsulated into GFP-F frames.



After Ethernet MAC frames are extracted from the received GFP-F frames, the IFGs are restored. The restoration of IFGs assures that sufficient bytes that contain 00 exist between consecutively received Ethernet MAC frames to meet the minimum IFG requirements (16 bytes).


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P-54

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



Source MAC address learning.



Forwarding based on the destination address.



Filtering based on the destination address



Flooding based on the destination address

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1. HUB is located in Physical Layer while LAN Switch is located in Data-Link Layer. 2. HUB: semi-duplex, data will broadcast to all the ports, lower efficiency. LAN Switch: full-duplex, through MAC self-learning get CAM table, avoid collision and enlarge the broadcast domain.

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Comparison between HUB and LAN Switch:



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An Ethernet switch or bridge has the following functions:





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Today, LAN switches are used to replace hubs in the wiring closet because user applications demand greater bandwidth.


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

Every LAN Switch has a MAC address table, which is the map of MAC address and port, and LAN Switch forwards the frames based on the MAC address table.



Source address learning is the process of obtaining the MAC address of devices. When a bridge is first turned on, it has no entries in its bridge table. As traffic passes through the bridge, the sender's MAC address is stored in a table along with the associated port on which the traffic was received.



As we see in the diagram - If PC A sends a frame to PC D, the Switch receives the frame on port 1, first, it looks at the destination MAC address, and checks the MAC address table, if the table has no entry which matches the destination MAC address the LAN Switch sends the frame to all the other ports, it will then write the source MAC address of the received frame into the table. This establishes the mapping relationship between the port 1 and the MAC address of PC A. Using this method, each switch will establish the mapping relationship and the MAC address table can be populated.

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

When a bridge does not have an entry in its bridge table for a specific address, it will transparently forward the traffic through all its ports except the source port. This is known as flooding. The source port is not "flooded" because the original traffic came in on this port and already exists on that segment. Flooding allows the bridge to learn, as well as stay transparent to the rest of the network, because no traffic is lost while the bridge is learning. After the bridge learns the MAC address and associate port of the devices to which it is connected, the benefits of transparent bridging can be seen by way of filtering. Filtering occurs when the source and destination are on the same side (same bridge port) of the bridge.


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When a frame arrives at a switch interface, the destination hardware address is compared to forward/filter MAC database. 

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If the destination hardware address is known and listed in the database, the frame is only sent to correct interface.



If the destination hardware address is not listed in the MAC database, then the frame is broadcasted out all active interfaces except the interface the frame was received on. While a device answers the broadcast, the MAC database is updated.



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Maximum Age:

Each CAM table has its capacity, it only can contain limited MAC database. So CAM table set a timer, the default value of the timer is 5 minutes. If the destination hardware address don’t use the database in CAM table for 5 minutes,

the timer will be initialized, and that database in the table will be deleted.



Ageing is required to keep the address table fresh.



Devices may be moved from port to port which could lead to traffic being sent out of the wrong port.


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Cut-Through Mode 

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Switches operating in cut-through mode receive and examine only the first 6 bytes of a frame. These first 6 bytes cover the destination MAC address, which has

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sufficient information to make a forwarding decision. Although cut-through switching offers the least latency when transmitting frames, it is may transmit fragments created during Ethernet collisions, corrupted frames. 

Fragment-Free Mode 

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Switches operating in fragment-free mode receive and examine the first 64 bytes of frame. Why examine 64 bytes? In a properly designed Ethernet network, collision fragments must be detected in the first 64 bytes.

Store-and-Forward Mode 

Switches operating in store-and-forward mode receive and examine the entire frame, resulting in the most error-free type of switching, however this is also the slowest type of switching.


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

Layer 2 switches separate the network in to collision domains, so if a hub is attached to each port there will be a collision domain on each port.



But the switch and the LANs connected to the switch form a Broadcast Domain. Any

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broadcast packets will be flooded across the whole domain, and all connected devices will receive the broadcast packet .if there are many broadcast packets in a domain, it may occupy a large part of the available network bandwidth and because these broadcasts may go to areas of the network where they are not needed this will reduce the efficiency of the network.

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





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The message of one VLAN will not be received by the hosts in other VLANs;

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When the network scale increases, the failure in part of the network will influence the whole network. After introducing the VLAN, some network failure can be limited within one;

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The VLAN can effectively solve the performance declining problem caused by the broadcast storm;

Strengthen the network robustness: 

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Enhance the communication security: 

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Improve the bandwidth utilization rate:

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

As the VLAN makes the segmentation on the network logically, the flexible networking solution and simple configuration management reduce the management and maintenance cost.

Broadcast Control: 

All ports in the same VLAN will filter the broadcast, different VLAN members can not received the broadcasts.


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

The four-byte 802.1q tag head contains a 2-byte Tag Protocol Identifier field (TPID) and a two-byte Tag Control Information (TCI) field.



TPID (Tag Protocol Identifier) is a new type field defined by the IEEE, indicating that the

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frame carries an 802. 1Q tag. The TPID contains a fixed value of 0x8100. 

The TCI contains the frame control information including the following elements: 

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Canonical Format Indicator (CFI): This is used to indicate the bit encoding format of the address in the frame. If the CFI value is 0, it indicates the standard format for Ethernet. If it is 1 it indicates a non-standard format which is used in token ring or FDDI.

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Priority: Three bits indicate the frame priority with a total of 8 priority levels ranging from 0 - 7. This is specified by the IEEE 802.1p standard.



VLAN Identifier (VLAN ID): This 12-digit field indicates the VLAN ID which can support a total of 4096 VLANs.

In switched networks Ethernet frames have two formats: 

Frames without the four-byte 802.1Q tag are called untagged frames;



Frames with the tag are called tagged frames.


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VLAN Based on port:

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

Normally VLAN 1 reserved for internal use.



In the figure, the port 1 and port 7 are designated to the VLAN 5, and the port 3

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and port 10 are designated to the VLAN 10. The host A and host C connect to the port 1 and port 7 respectively. Therefore they belong to the VLAN5. In this way, host B can not communicate with host A. 

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If there are several switches, you can designate that the ports 1~6 of the switch 1 and the ports 1~4 of the switch 2 belong to the same VLAN. That‘s to say, the same VLAN can cross several Ethernet switches. The port-based segmentation is the most commonly used method in defining the VLAN. The advantage of this segmentation method is that it is simple to define the VLAN members by only

defining all the ports. Its disadvantage is that the port should be defined again if the VLAN subscriber leaves the original port to a certain port of a new switch .


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The VLAN application has solved many problems occurred in the large-scale layer 2 switching network: 

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Improve the bandwidth utilization rate: The VLAN has effectively solved the performance declining problem caused by the broadcast storm;



Enhance the communication security: The message of one VLAN will not be received by the hosts in other VLANs;





Strengthen the network robustness: When the network scale increases, the failure in part of the network will influence the whole network. After introducing the VLAN, some network failure can be limited within one;

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L3 switch is needed if the hosts in different VLAN communicate with each other.

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UNI 

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UNI port in customer side, include tag, access and hybrid, UNI port can identify the VLAN tag of frame.

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

P1 refers to the original data, P2 refers to the processed data.



Receiving:



Input data without VLAN tag: Add Default VLAN;



Input data without VLAN tag: Discard.

Transmitting: 



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

Strip Default VLAN.

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In this case, set port attribute is Access, then the input data of VC trunk must with VLAN, so set the attribute of VC trunk is Tag aware.

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

Input data without VLAN tag: Discard;



Input data with VLAN tag: Transparent transport.

Transmitting: 



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Receiving:

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Transparent transport.

In this case, set port attribute is tag aware, then the input data of VC trunk must with VLAN, so set the attribute of VC trunk is Tag aware.

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P-68

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

Input data without VLAN tag: Add Default LAN;



Input data with VLAN tag: Transparent transport.

Transmitting:  



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Receiving:

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If the received VLAN ID is same as the Default VLAN ID: Strip Default VLAN; If the received VLAN ID is different with the Default VLAN ID: Transparent transport.

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In this case, set port attribute is Hybrid, then the input data of VC trunk must with VLAN, so set the attribute of VC trunk is Tag aware.

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Also can set the attribute of VC trunk is Hybrid in some occasion.

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

QinQ technology is a VLAN stacking technology, which conforms to the recommendation for S-VLAN in IEEE 802.1ad and is an expansion of VLAN technology.



Advantages of QinQ technology: 





Extends LAN service to WAN, connecting the client network to the carrier network and supporting transparent transmission.

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QinQ frame format:

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Expands VLAN and alleviates VLAN resource insufficiency. For example, a VLAN providing 4096 VLAN IDs can provide 4096 x 4096 VLANs after VLAN stacking;

DA

SA

TYPE(8100)

S-VLAN

TYPE(8100)

C-VLAN

Ethernet

(6B)

(6B)

(2B)

(2B)

(2B)

(2B)

Data

M



Customer VLAN label, defined as C-VLAN;



Server layer VLAN label, defined as S-VLAN.


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The transmission process of a QinQ packet in the above network model is as follows: 

When two service packets respectively containing C-VLAN1 and C-VLAN2 tags arrive at service provider network S1 through transmission equipment, the S-Aware

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port adds an S-VLAN tag defined by the service provider to the packets. Thus, the service packets contain two layers of VLAN tags during the transmission in the network. 

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When the service packets go from service provider network S1 into service provider network S2, the S-Aware port in service provider network S2 replaces the S-VLAN1 tag with a S-VLAN2 tag and the service packets are continuously transmitted in service provider network S2.



When the service packets arrive at the network at the side of the destination users,

the C-Aware port at the user side removes the S-VLAN2 tag and forwards the service packets to the destination users according to different C-VLAN tags.


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In a traditional IP network, all packets are treated in an undifferentiated way. Every router adopts the first in first out (FIFO) policy to process packets, and makes its best effort to transmit packets to the destination. In this case, the packet transmission performances such as the reliability and delay are not ensured. The constant development of networks and the emergence of new applications based on IP networks pose new requirements for the QoS of IP networks. Real-time services such as voice over IP (VoIP) services pose stringent requirements for the transmission delay of packets. An extremely long transmission delay is not acceptable to the user. Video conference and video on demand (VOD) services require ensured high bandwidth, low delay, and low delay jitter. Key tasks such as transactions and Telnet may not require a high bandwidth but require low delay, and thus these key tasks must be always handled first in the case of network congestion. Email and FTP services are not sensitive to time delay. To support voice, video, and data services that have different service requirements, a network must be able to differentiate communication types so as to provide relevant services.

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QoS: Quality of Service (QoS) refers to the ability of a communication network to ensure the expected service quality in the aspects of bandwidth, delay, delay jitter, and packet loss ratio, therefore ensuring that the request and response from the user or the request and response from the application meet the requirements of an expected service class. The following illustrates the sending of packets in an FIFO queue and a priority queue: 



FIFO queue: All packets to be transmitted through this interface enter the tail of the FIFO queue according to the sequence of their arrival at the interface. The interface transmits these packets from the head of the queue. The packets are not differentiated during the transmission, and the quality of packet transmission is not ensured. Priority queue: After packets arrive at the interface, the packets are classified first. Then, these packets enter the tail of their corresponding queues according to their types. In this manner, the higher-priority packets are always transmitted first and these packets have low delay jitter. In addition, the performance indexes of these packets, including the packet loss ratio and delay jitter, can be ensured even in the event of network congestion.


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Flow classification: A flow refers to a group of packets that have the same characteristics. By using the specified rules, flow classification identifies packets that meet different types of characteristics. It is the precondition and basis for providing differentiated services. Flow classification can be classified into two types, namely, complex flow classification and simple flow classification.

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Traffic policing: The typical function of traffic policing is to supervise the rate of traffic and to ensure that the rate of traffic does not exceed the committed rate. If the traffic of a connection exceeds the committed rate, some packets can be discarded or the packet priorities can be re-set through the traffic policing function.

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Traffic marking: Traffic marking lets another application system or device that processes a packet know the type of the packet and perform the predefined processing for the packet.

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Basic concepts of QoS:

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Queue scheduling: Queue scheduling is used for implementing congestion management. When a congestion happens on an outgoing port, a proper queue scheduling mechanism can ensure that a type of packets can first be sent. The queue scheduling mechanisms include FIFO, PQ, CQ, WFQ, CBWFQ, LLQ, and IP RTP. Traffic shaping: It can restrict the traffic and burst of a connection in a network, and enables the packet to be transmitted at an even rate.

Packet processing: 

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At the ingress port, the network equipment classifies the traffic, measures rates, and differentiates CoSs for packets. In this manner, the equipment labels the packets according to flow classification, CAR results, and CoS rules. Then, the equipment forwards the packets to the egress port, according to a forwarding algorithm. At the egress port, the packets are classified again for identifying the packets that require traffic shaping. According to the labels added at the ingress port, the packets enter the queues of relevant priorities and wait for scheduling.


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It is the default mode for all traffic. Internet was initially based on a best-effort packet delivery service. Its queuing algorithm is FIFO.

IntServ model 

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The Integrated Service (IntServ) model expects applications to signal their requirements to the network on demand. The bandwidth should be reserved according to application. The signal protocol is RSVP.

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DiffServ model

DiffServ provides the greatest scalability and flexibility in implementing QoS in a network. Network devices recognize traffic classes and provide different levels of QoS to different traffic classes.

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Integrated service is an integrated service model that meets various QoS requirements. Before sending packets, the service model should apply specific service to the network. This request is accomplished by signaling. The application program first notifies the network about its traffic parameters and the required specific service quality including bandwidth and delay etc. After the application program receives network confirmation (that is, the network confirms to reserve resources for packets of the application program), it begins sending packets. Meanwhile, packets sent by the application program should be controlled within the range of traffic parameter description.

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After the network receives the resource request from the application program, it executes the resource admission control to judge whether to assign resources for the application program according to the resource request and current network resource condition. Once the network determines to assign resource for packets of the application program, it will ensure the QoS requirements to the application program so long as the packets are controlled within the range of traffic parameter description. The network will maintain a state for each flow (decided by IP address of two ends, port number and protocol number), and execute packet classification, traffic policing, queuing and dispatching to accomplish its permission to the application program according to this state.

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In the differentiated service (DiffServ) model, services are described by the traffic classifier.

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The flows are classified and marked on the ingress router in the DiffServ domain.

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The internal NE perform corresponding PHB according to the classification marking of the packets and need not perform complex traffic classification. PHB stands for per-hop behavior. It is the action performed to the traffic by a NE, for example, expedited forwarding, re-marking, and dropping of packets. The traffic classification marking is contained in the packet header and transmitted in the network with the data. Therefore, the router need not maintain the status information for the flows. (In integrated service model, the router must maintain the status information for each flow.) The service that a packet can obtain is related to the marking of the packet. The ingress NE and egress NE of a DiffServ (DS) domain are connected to other DS domains or non-DS domains through links. Different administrative domains may apply different QoS policies, so the administrative domains must negotiate the Service Level Agreement (SLA) and establish the Traffic Conditioning Agreement (TCA). The inbound traffic to the ingress router and the outbound traffic to the egress router must comply with the TCA.

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The DiffServ (DS) domain consists of a group of network nodes (DS nodes) that provide the same service policy and realize the same per-hop behavior (PHB).

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The DS nodes are of two types, namely, DS edge nodes and internal DS nodes. The DS edge node classifies the traffic that enters the DS domain. The DS edge node marks different PHB service levels according to different types of service traffic. The internal DS node controls the flow based on the PHB service levels.


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Complex flow classification means fine packet classification by use of complex rules such as information (for example, source MAC address, destination MAC address, source IP address, destination IP address, user group number, protocol type, and TCP/UDP port of an

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application) about the link layer, network layer, and transport layer. 

Simple flow classification means coarse packet classification by use of simple rules such as Type of Service (ToS) field in IP packets, user priority, or EXP field in MPLS packets. Simple flow classification is used to identify flows with different priorities.

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Port flow: The packets from a certain port are classified as a type of flow. The Ethernet services associated with such a flow are Ethernet private line services whose service source is the port. The Layer 2 switch services from VB logic port can be classified as port flow.

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Port+VLAN flow: The packets that are from a certain port and have a specified VLAN ID are categorized as a type of flow. The Ethernet services associated with such a flow are Ethernet private line services whose service source is the port+VLAN.

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Port+S-VLAN flow: The packets that are from a certain port and have a specified S-VLAN are classified as a type of flow. The Ethernet services associated with such a flow are EVPL (QinQ) or EVPLAN (802.1ad bridge) services whose service source is the port+S-VLAN.

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Port+C-VLAN+S-VLAN flow: The packets that are from a certain port and have a specified C-VLAN+S-VLAN are classified as a type of flow. The Ethernet services associated with such a flow are EVPL (QinQ) or EVPLAN (802.1ad bridge) services whose service source is the port+C-VLAN+S-VLAN.

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srTCM algorithm:  Tokens enter the two token buckets at the CIR. Every token represents a number of bytes. If the packets that arrive at the buckets do not exceed the CBS, they are marked green. If the packets that arrive at the buckets exceed the CBS but do not exceed the EBS, they are marked yellow. If the packets that arrive at the buckets exceed the EBS, they are marked red. The red packets are directly discarded. In the case of network congestion, the green packets can always pass first and the yellow packets are discarded. trTCM algorithm:  Tokens enter the two token buckets respectively at the PIR and CIR. Each token represents a number of bytes. When the rate of the packet exceeds the PIR, the packet is marked red. When the rate of the packet is between the PIR and the CIR, the packet is marked yellow. When the rate of the packet does not exceed the CIR, the packet is marked green. The red packet is discarded directly. In the case of network congestion, the yellow packet is first discarded and the green packet is always transmitted first. Parameters:  CIR: Committed information rate  PIR: Peak information rate  EBS: Excess burst size  CBS: Committed burst size  PBS: Peak burst size

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Packets are classified according to the preset matching rules. The packets whose flow performance is not defined are directly transmitted without being processed in the token bucket. The packets that require traffic control enter the token bucket for processing.

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The token bucket can be considered as a container of tokens, and it has a certain capacity. Tokens are placed into the bucket at a rate specified by the user. The user can also set the

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capacity of the token bucket, so that no more tokens can be placed into the bucket when the number of tokens is greater than the capacity of the bucket. 

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When the packets are processed in the token bucket, the packets can pass and be transmitted if the token bucket have sufficient tokens to transmit the packets. In this case, the number of tokens in the bucket decreases according to the length of the transmitted packets. When the number of tokens in the bucket is so small that no more packets can be

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transmitted, the remaining packets are discarded or marked. In this manner, the traffic control is performed for a certain type of packets. When the token bucket is filled with tokens, the packets that are represented by these tokens can be transmitted, which allows the transmission of the burst data. When no tokens are available in the token bucket, packets cannot be transmitted until new tokens are generated in the bucket. This ensure that the traffic of packets is not more than the rate at which the tokens are generated. Hence, the traffic control is achieved.


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The token bucket contains tokens instead of packets. A token is generated and added to the token bucket every △t period. When the token bucket is full, the new token is dropped.

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A token permit to send a single (or, in some case, a byte) of packet. A packet can be forwarded when there are enough tokens in the token bucket. The number of tokens

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decreased accordingly, depending on the packet size. If there are not enough tokens, the packet is dropped and the number of token does not change. 

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The Ethernet processing board that supports the QoS assesses traffic by using the single rate three color marker (srTCM, which complies with RFC 2697) algorithm or the two rate three color marker (trTCM, which complies with RFC 2698) algorithm. Packets are marked in green, yellow, or red according to the assessment results. Based on the packet colors,

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the packets are marked with different priorities in the case of discarding. The srTCM algorithm is defined for the burst of packet size. The two rate three color marker (trTCM) algorithm, however, is defined for the burst of packet rate.


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CoS: Packets are scheduled into certain queues of different priorities and then transmitted depending on the priority of each queue. As a result, the packets in the queues of different priorities are transmitted according to their QoS policies, such as delay and bandwidth. 

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With the four types of CoSs configured, packets can be scheduled to egress queues of different priorities. Simple CoS: When a flow is configured with the simple CoS, all packets of the flow are scheduled to a specified egress queue, regardless of the packet type and contents of the flow.

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VLAN priority CoS: When a flow is configured with the VLAN priority CoS, the packets of the flow are scheduled to a specified egress queue according to the VLAN priority value carried in the packets. The classification of VLAN priorities is based on the Pri field defined by IEEE 802.1Q. If the user uses the same VLAN to carry services, and if the classification of priorities for the service flows is completed before the services access the network, the system is able to determine the CoS of the data packets according to the Pri-to-CoS mapping relations.

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IP TOS CoS: When a flow is configured with the IP TOS CoS, the packets of the flow are scheduled to a specified egress queue according to the IPv4 IP TOS value carried in the packets. This type of CoS is applicable to a data flow containing IP packets only. DSCP CoS: When a flow is configured with the DSCP CoS, the packets of the flow are scheduled to a specified egress queue according to the IPv6 IP DSCP (Differentiated Services Code Point) value carried in the packets. This type of CoS is applicable to a data flow containing IP packets only.


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The srTCM algorithm is adopted for traffic shaping. In addition, buffer queues are added before the token bucket. When service packets exceeds the capacity of the token bucket, they are buffered in the corresponding queues.

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When a packet does not obtain a Tp token, the packet is placed into the Tp buffer queue. When the Tp buffer queue overflows, the overflowed packet is directly discarded.

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Traffic shaping is usually realized by using a buffer and a token bucket. When the packet transmission rate is very high, the packets are stored in the buffer. Under the control of the token bucket, the buffered packets are then evenly transmitted. In this manner, the traffic shaping function prevents packet loss in case that the fluctuating traffic transiently exceeds the bandwidth, and prevents the impact of huge traffic on the downstream equipment.

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If a packet obtains a Tp token but no Tc token, the packet is placed into the Tc buffer queue. When the Tc queue overflows, the overflowed packet is marked in yellow and then placed into the egress queue so that the packet is first discarded in the case of a network congestion. If a packet obtains a Tc token, the packet is directly placed into the egress queue.

The optional parameters for traffic shaping include CIR and CBS. CIR is the committed bandwidth and CBS is the committed burst size.  

Committed bandwidth: Shaping bandwidth configured for a queue Extra bandwidth: Remaining bandwidth after all committed bandwidths that should be allocated are deducted from the total bandwidth of a port.


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The SP queue scheduling algorithm is designed for key service applications. A key service must be processed with the highest priority when congestion occurs so that the response delay can be shortened. For example, a port provides eight egress queues, which are

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allocated with priorities from 7 to 0 in a descending order. 

During the SP queue scheduling, packets are transmitted in a descending order of priorities. When a queue with a higher priority is empty, the packets in the queue with a lower priority can be transmitted. In this manner, packets of key services are placed into the queues with higher priorities and packets of non-key services (such as email services) are placed into queues with lower priorities. Therefore, the packets of key services can be always transmitted first, and the packets of non-key services are transmitted when the data of key services is not processed.

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For example, a port provides four queues. In an order of priorities, the WRR configures the w3, w2, w1, and w0 weights for the four queues. Each weight stands for the proportion of resources that the relevant queue can obtain from the total resources. If this port is a 100 Mbit/s port and the weights of its four queues are set to 50, 30, 10, and 10 (corresponding to w3, w2, w1, and w0) by the WRR scheduling algorithm, a minimum of 10 Mbit/s bandwidth is guaranteed for the queue with the lowest priority. This prevents the disadvantage that packets in the queues with lower priorities may fail to obtain services for a long time in the case

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The Weighted Round Robin (WRR) scheduling algorithm divides each port into several egress queues and schedules the packets in these queues in turn. This ensures that each queue obtains a certain service period. 

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Another advantage of the WRR scheduling is as follows: Although scheduling of multiple queues is performed in the polling manner, time segment allocated to each queue is not fixed. That is, when a queue is empty, the packets in the next queue are scheduled immediately. In this manner, the bandwidth resources can be fully utilized.


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The SP+WRR scheduling algorithm sets one of the egress queues as an SP queue, and therefore the packets in this queue are always first scheduled. This setting can ensure that the key services are always fist processed. The other egress queues adopt the WRR

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scheduling algorithm, and therefore each queue can obtain a certain period of service. 

For example, a port provides eight queues, among which queue 7 is an SP queue. In this case, the committed bandwidth for queue 7 is always fist provided. For queues 0 to 6, the WRR scheduling is performed according to the 1:2:4:8:16:32:64 weight allocation, and at each service time segment the packets in the corresponding queue are transmitted. If the queue that corresponds to a service time segment does not have packets, this service time segment is removed and the packets in the queue that corresponds to the following service time segment are

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To enable packets in low-priority queues to obtain the opportunity of fair scheduling and share network resources in a fair manner, and to optimize the delay and jitter of all flows as much as possible, the FQ scheduling technology emerges. According to the idea of the

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FQ scheduling, the equipment schedules different queues cyclically so that the queues obtain the opportunity of fair scheduling and the delays of different packet flows are balanced on a whole. Later, a bandwidth allocation weight is added on the basis of the FQ to form the WFQ (Weighted Fair Queuing) technology in which queues are scheduled according to the weights. 

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When WFQ scheme is used, queues are scheduled in a fair manner according to the weight allocated to each queue. Generally, larger weights and bandwidths are allocated to the higher-priorities queues, and smaller weights and bandwidths are allocated to lower-

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One output queue adopts the SP scheduling algorithm to guarantee that key services are first scheduled and processed. Other output queues adopt the WFQ scheduling algorithm to guarantee that each of them obtains a certain bandwidth. 

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For example, a port provides eight output queues. Queue 7 is an SP queue and the committed bandwidth of the queue is first guaranteed. Bandwidth is allocated to queue 0 to queue 6 according to the weight proportions of 1:2:4:8:16:32:64. Hence, all the packets in queue 0 to queue 6 can be transmitted according to the committed bandwidth of each queue.

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The combination of the SP and WFQ algorithms not only overcomes the defect that packets in low-priority queues cannot obtain a bandwidth in a long period of time, but also guarantees that time-sensitive services (for example, voice service) are first scheduled.

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For example, a port provides four output queues. Queue 4 is an SP queue and the packets in queue 4 are first scheduled. Bandwidths are allocated to queue 1 to queue 3 according to the weight proportions of 1:2:4.


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1. The priority of a queue with the traffic shaping function enabled is higher than the priority of a queue with the traffic shaping function disabled. 2. When the traffic shaping function is enabled (or disabled) for all eight queues, queue 8 has the absolute priority, and the remaining bandwidth is allocated to queues 1-7 in the proportion of 1:2:4:8:16:32:64.

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For example, you can enable the traffic shaping function for queues 6 and 7, and disable the traffic shaping function for the other queues. According to the first priority rule, the priorities of queues 6 and 7 are higher than the priorities of the other queues, and thus queues 6 and 7 are first allocated with the configured CIR bandwidth. Then, according to the second priority rule, the priority of queue 8 is higher than the priorities of queues 1-5. In this case, after the required bandwidth is allocated to queues 6 and 7, the remaining bandwidth is first allocated to queue 8, and then allocated to queues 1-5 according to the bandwidth proportion.

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For example, if a port supports eight queues, the egress port scheduling rules are as follows: 

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Packet Switch Principle

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1 Data Communication Network Overview...................................................Page3 2 IP Addressing..........................................................................................Page21

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3 QinQ Technology....................................................................................Page41

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4 MPLS Technology....................................................................................Page48 5 PWE3 Technology...................................................................................Page73

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A network is a complex system interconnected formed by interconnected people or things. Networks exist everywhere in our life, for example, the telephony network and telegraph network. There are also many network systems in one's body, for example,

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the nerve system and the digestive system.

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The computer network is a large-scale and powerful system that connects computers and peripheral devices in different areas through communication lines. In the

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computer network, substantive computers can exchange information and share information resources. The computer network was developed to meet the requirement

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In the initial stage of the computer network, each computer is an independent device. Computers work independently and do not communicate with each another. Combination of the computing technology and communication technology brings a far-reaching influence to the organization of the computer system and makes possible the communication among computers. Computers of different types use the same protocol to communicate, and thus the computer network comes into being.



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Element of Data Communication Network in Equipment：

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End Equipment(User Equipment)：End equipment is an interface equipment between users and communication network，which can transfer user’s

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message into electric signal . At the same time, end equipment also can transfer electric signal into user’s message. 

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Transfers System：Transfers system is the channel used to transfer electric signal，including wire,wireless,fiber etc. Switching Equipment：Switching equipment is used to carry out routing choice,switch control between end equipment and other equipment.

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In recent years, the computer network is developing rapidly. The computer communications network and the Internet have become the basic part of the society. The computer network is applied to many fields of industry and commerce, including e-bank, e-commerce, modernized enterprise management , and information service. Remote education, government routines, and community cannot work without the network technology. The saying "network exists everywhere in the world" is not an exaggerated statement.

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The computer network came into being in 1960s. At that time, the network was a host-based low-speed serial connection providing program running, remote printing, and data service. The System Network Architecture (SNA) of IBM and X.25 public data network are such kind of network. In 1960s, the defense department of US funded a packet switching network called ARPANET, which was the earliest rudiment of the Internet.

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In 1970s, the commercial computing mode, which featured personal computers, came forth. Initially, personal computers were used as independent devices. Because of the complexity of commercial computing, many terminal devices needed to cooperate, and thus the local area network (LAN) was developed. The LAN lowers the expense on printers and disks dramatically.

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In 1980s and 1990s, to deal with the increasing demand on remote computing, the computer industry developed many wide area network protocols (including TCP/IP and IPX/SPX). Then the Internet was expanded fast. Now TCP/IP is extensively used on the Internet.



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The Internet is a large network formed by networks and devices. Based on the covered geographic scope, networks are classified into LAN, WAN, and Metropolitan Area Network (MAN) whose size is between the LAN and WAN.

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Local Area Network (LAN)

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A LAN is formed by connected communication devices in a small area. A LAN covers a

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Wide Area Network (WAN)

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A WAN covers a larger geographic scope, such as a state or a continent. It provides the data communication service in a large area and is used to connect LANs. The China

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A LAN is formed by interconnected communication devices in a small area. In general, a LAN covers several kilometers. The LAN is featured by short distance, low delay, high data transmission speed, and high reliability. Common LANs are Ethernet and Asynchronous Transfer Mode (ATM). They are different in topology, transmission speed, and data format. Ethernet is the most widely used LAN. The following network devices are used in LAN construction:  Cables: A LAN is extended by cables. Various cables are used in LANs, for example, the fiber, twisted pair, and coaxial cable.  Network Interface Card (NIC): An NIC is inserted in the main board slot of a computer. It transforms the data to the format that other network devices can identify and transmits the data through the network medium.  Hub: A hub is a shared device that provides many network interfaces to connect computers in the network. The hub is called a shared device because all its interfaces share a bus. At a moment, only one user can transmit data, and so the data amount and speed of each user (interface) depends on the number of active users (interfaces).  Switch: also called a switched hub. A switch also provides many interfaces to connect network nodes but its performance is much higher than that of a shared hub. It can be considered to have many buses so that devices connected to each interface can independently transmit data without affecting other devices. For users, the interfaces are independent of each other and have fixed bandwidth. In addition, a switch has some functions that a hub lacks, such as data filtering, network segmentation, and broadcast control.  Router: A router is a computer device used to connect networks. A router works at the third layer (network layer) of the OSI model and is used to route, store, and forward packets between networks. Generally, a router supports two or more network protocols so that it can connect networks of different types. A router can also run dynamic routing protocols to dynamically route packets.  ATM switch: used to connect ATM networks. Confidential Information of Huawei. No Spreading Without Permission

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A WAN covers a larger geographic scope, such as a state or a continent. A WAN connects LANs that are far from each other. It consists of the end system (users on two ends) and the communication system (the link between two ends). The communication system is the key of the WAN and it falls into the following types:  Integrated Service Digital Network (ISDN): a dial-up connection mode.  Leased Line: called DDN in China. It is a point-to-point connection that transmits data at the speed of 64 kbps to 2.048 Mbps. The leased line guarantees data transmission and provides constant bandwidth, but the cost is high and the pointto-point structure is not very flexible.  X.25: a WAN type that appeared early and is still in extensive use at present.  Frame Relay: a new technology developed on the basis of X.25.  Asynchronous Transfer Mode (ATM): a cell exchange network that features high speed, low delay, and guaranteed transmission quality. Most of ATM network use fibers as the connection medium. The fiber provides a high speed of over 1 gigabit, but the cost is also high. ATM is also a WAN protocol. In the WAN, access is implemented through various serial connections. Generally, enterprise networks are connected to the local ISP through the WAN lines. The WAN provides fulltime and part-time connections. In the WAN, serial interfaces can work at different speeds. The following devices are used in the WAN:  Router: The process of looking for the transmission path is called routing. A router establishes routes between WANs and LANS according to the addresses and sends the data to the destination.  Modem: As the device used to transform signals between the end system and communication system, a modem is the indispensable device in a WAN.

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A complete IP network consists of the backbone network, MAN, and access network.  Backbone network: a network connecting networks of different countries and cities.  MAN: the network between the backbone network and access network. It connects networks of different areas in the same city. A MAN consists of the core layer, convergence layer, and access layer.  Access network: layer-2 network under the access control policy. The access network is responsible for access of end users. Users can connect to the Internet through xDSL and Ethernet.

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The target networks of the IP MAN are:  IP MAN  The IP MAN is a layer-3 routing network consisting of access control points (the BRAS and service router) and the upstream routers.  The IP MAN consists of the core layer, convergence layer, and service access control layer.  Broadband access network  The broadband access network is the layer-2 access network under the access control point.  The broadband access network consists of the layer-2 convergence network and the last-mile access network. The service plane logically falls into the access network plane for the public and the access network plane for key customers.

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Many international standardization organizations made great contributions to development of the computer network. They unify network standards so that devices of different vendors can communicate with each other. Till now, the following standardization organizations have made contributions to development of the computer network. International Organization for Standardization (ISO)：ISO stipulates standards for large-scale networks, including the Internet. The ISO brings forward the OSI model that describes the working mechanism of network. The OSI model is a comprehensible and clear hierarchical model of the computer network. Institute of Electrical and Electronics (IEEE)：IEEE defines standards for network hardware so that hardware devices of different vendors can communicate with each other. The IEEE LAN standard is the dominant standard for LANs. IEEE defines the 802.X protocol suite. 802.3 is the standard for the Ethernet; 802.4 is the standard for the token bus network; 802.5 is the standard for token ring; 802.11 the standard fro the wireless local area network (WLAN). American National Standards Institute (ANSI)：ANSI is an organization formed by companies, governments, and other members voluntarily. The ANSI defines the standard for the fiber distribution data interface. Electronic Industries Association/Telecomm Industries Association (EIA/TIA)：They define the standards for network cables, for example, RS232, CAT5, HSSI, and V.24. They also define the standard for cabling, for example, EIA/TIA 568B. International Telecomm Union (ITU)：They define the standard for the telecom network working as the WAN, for example, X.25 and Frame Relay. Internet Engineering Task Force (IETF)：Founded at the end of 1985, the IETF is responsible for researching and establishing technical specifications related to the Internet. Now IETF has become the most authoritative research institute in the global Internet field.

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Since 1960s, computer network has undergone a dramatic development. To take the leading position and have a larger share in the communication market, manufacturers competed in advertising their own network structures and standards which included IBM’s SNA, Novell’s IPX/SPX., Apple’s Apple Talk, DEC’s DECnet and TCP/IP, the most widely used nowadays. At the same time, these companies pushed software and hardware that use their protocols to the market enthusiastically. All these efforts promoted the fast development of network technology and the prosperity of the market of network devices. However, on the other hand, the network became more and more complicated due to the various protocols and communications became more and more difficult since networks using different protocols were not compatible with each other. To improve network compatibility, the International Organization for Standardization (ISO) in 1984 developed the Open System Interconnection Reference Model (OSI RM) which soon became the model of network communications. The ISO followed the following principles when they designed the OSI reference model:  Each layer of the model has its own responsibilities which should help it stand out as a distinct layer.  To avoid function overlapping, there should be enough layers. The OSI reference model has the following advantages:  It simplifies network related operations.  It provides compatibility and standard interfaces for systems designed by different institutions.  It enables all producers to be able to produce interoperationable network devices, which facilitates the standardization of networks.  It lays the complex concept of communications down into simpler and smaller problems, which facilitates our understanding and operations.  It separates the whole network into areas, which guarantees changes in one area will not affect other areas and networks in each area can be updated quickly and independently. Confidential Information of Huawei. No Spreading Without Permission

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The functions of each layer of the OSI reference model are listed as follows: Physical layer: providing a standardized interface to physical transmission media including power level, line speed and mechanical specification of electrical connectors and cables.

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Data link layer: provides a service to the network layer.It encapsulates the network Iayer information in a frame (the layer 2 PDU).

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Network layer:

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Provide logical addresses for transmission across networks.

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Routing: to forward packets from one network to another.

Transport layer: providing reliable or unreliable data transfer services and error check before retransmission. Session layer: establishing, managing and terminating the connections between the local and remote application. Service requests and responds of application programs in different devices form the communication of this layer RPC,NFS and SQL belong to this layer. Presentation layer: providing data encoding, encryption and ensuring that the data sent by the application layer of one system can be understood by the application layer of another system.

Application layer: providing network services as the closest layer to users among the seven layers. Confidential Information of Huawei. No Spreading Without Permission


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Since the OSI reference model and protocols are comparatively complicated, they do not spread widely. However, TCP/IP has been widely accepted for its openness and simplicity. The TCP/IP stack has already been the main stream protocols for the

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The TCP/IP model also takes a layered structure. Each layer of the model is independent from each other but they work together very closely. The difference

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Each layer of the TCP/IP model corresponds to different protocols. The TCP/IP protocol stack is a set of communication protocols. Its name, the TCP/IP protocol suite, is named after two of its most important protocols: the Transmission Control Protocol

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(TCP) and the Internet Protocol (IP) . The TCP/IP protocol stack ensures the communication between network devices. It is a set of rules that define how

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The router is a common network device that works at the network layer. Routers

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Each layer of the TCP/IP model uses protocol data unit (PDU) to exchange information and enable communication between network services. PDUs of different layers carry different information, and so they are named differently. For example, the transport layer adds TCP header to the PDU from the upper layer to form the layer 4’s PDU, which is called segment. And then segments are delivered to the network layer. And they become packets after the network layer puts the IP header into those PDUs. The packets are transmitted to the data link layer, where they are added data link layer headers to become frames. Finally, those frames are transformed into bit stream to be transmitted through network medium . This process in which data are delivered following the protocol suite from the top to the bottom and are added with headers and tails is called encapsulation.

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After encapsulation, data is sent to the receiving device after transmission. The receiving device will decode the data to extract the original service data unit and decides how to pass the data to an appropriate application program along the protocol stack. This reverse process is called decapsulation. The matching layer, or peer, of different devices communicates through encapsulation and decapsulation.

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As the figure above shows, Host A is communicating with Host B. Host A delivers data transformed from an upper layer protocol to the transport layer. The transport layer encapsulates its header in front of the data and passes it to the network layer. Then the network layer keeps the data it received as its own data and adds its header to it before delivers it to the data link layer. The data link layer encapsulates its header into the data and then passes it down to the physical layer. The physical layer then transforms the data into bit stream and sends it to Host B through the physical line.

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When Host B receives the bit stream, it sends it to its data link layer. The data link layer extracts the data link layer packet out and passes the left to the upper layer, the network layer. Then the network layer deletes the IP header from the packet and

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passes it to the transport layer. In the similar way, the transport layer extracts the original data and delivers it to the top layer, the application layer.

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The data link layer ensures that datagram are forwarded between devices on the same network, while the network layer is responsible for forwarding packets from source to destination across networks.

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In the above figure, Host A and Host B reside on different networks or links. When the router that resides on the same network as Host A receives frames from Host A, the router passes those frames to the network layer after it ensures that the frames should be sent to itself by analyzing the frame header. Then the network layer checks where those frames should go according to the destination address in the network layer header and later it forwards those frames to the next hop. The process repeats until the frames are sent to Host B.

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As the slide shows, this procedure is called encapsulation, in which data is transferred along the TCP/IP protocol stack, from the upper layer downward, meanwhile, relative header and tail are added. After the data encapsulation and transmission in the network, the receiving equipment will delete the information added, and decide how to deliver the data to proper application along the TCP/IP protocol stack, according to the information in the header.

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Among different layers of TCP/IP model, information is exchanged to ensure the communication between network equipment. The PDU is used for exchanging information. The PDU is different for different layers, and with different names. For instance, in the transport layer, the PDU with TCP layer is called segment; after the segment is transmitted to network layer, and added with IP header, the PDU is called packet. Then, the PDU with layer 2 header is called frame. Finally, the frame is changed into bits, and are transmitted through network media. Confidential Information of Huawei. No Spreading Without Permission


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The LAN is featured by short distance, low delay, high data transmission speed, and high reliability. A LAN is formed by interconnected communication devices in a small area.In general, a LAN covers several kilometers. A WAN covers a larger geographic scope. A WAN connects LANs that are far from each other. The WAN operates in a scope larger than that of the LAN. The functions of each layer of the OSI reference model are listed as follows:  Physical layer: providing a standardized interface to physical transmission media.  Data link layer: provides a service to the network layer.It encapsulates the network Iayer information in a frame (the layer 2 PDU).  Network layer: providing logical addresses for routers to decide routes.  Transport layer: providing reliable or unreliable data transfer services and error check before retransmission.  Session layer: establishing, managing and terminating the connections between the local and remote application.  Presentation layer: providing data encoding, encryption and ensuring that the data sent by the application layer of one system can be understood by the application layer of another system.  Application layer: providing network services as the closest layer to users among the seven layers. Each layer of the TCP/IP model is independent from each other but they work together very closely. Each layer of the TCP/IP model uses protocol data unit (PDU) to exchange information and enable communication between network services. PDUs of different layers carry different information, and so they are named differently. For example, the transport layer adds TCP header to the PDU from the upper layer to form the layer 4’s PDU, which is called segment. And then segments are delivered to the network layer. And they become packets after the network layer puts the IP header into those PDUs. The packets are transmitted to the data link layer, where they are added data link layer headers to become frames. Finally, those frames are transformed into bit stream to be transmitted through network medium . This process in which data are delivered following the protocol suite from the top to the bottom and are added with headers and tails is called encapsulation.After encapsulation, data is sent to the receiving device after transmission. The receiving device will decode the data to extract the original service data unit and decides how to pass the data to an appropriate application program along the protocol stack. This reverse process is called decapsulation. The matching layer, or peer, of different devices communicates through encapsulation and decapsulation.

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The network layer receives data from transport layer, and adds source address and destination address into the data.

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IP address is composed of 32 bits, which are divided into four octets, or four bytes.

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The IP address could be represented in the following methods:

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Dotted decimal format:10.110.128.111

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Binary format：00001010.01101110.10000000.01101111

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Hexadecimal format:0a.7e.80.7f

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The hierarchy scheme makes IP address is compose of two parts: network part and host part.

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IP address is a collection of 32 binary digits. Usually, it is represented by 4 bytes (each byte is composed of 8 binary digits). Every 8 binary digits correspond to a decimal number.

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Decimal counting system is based on the power of 10: 101 , 102 , etc. And binary counting system is based on the power of 2: 21 , 22 , etc.

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In a byte, from the right to the left bit, they are corresponding 20 , 21 , 22 … 27.

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As the slide shows, for this byte, from left to right, the decimal number represented

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The sum of them is 255. Thus, the byte (8 bits) with all “1” represents 255 in decimal.

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As this slide shows, for “11101001”, calculate every bit of it into corresponding decimal number. Then convert this binary to the decimal number.

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The network layer adds the IP header to TCP datagram which it receives from the transport layer. Usually, the IP header has a fixed length of 20 bytes which does not include the IP options.

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The IP header consists of the following fields:

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Version: indicates the version of the IP protocol. At present, the version is 4. The version is 6 for the next generation IP protocol.

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IP header length is the number of 32-bit words forming the header including options. Since it is a 4-bit field, its maximum length is 60 bytes.

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TOS: 8 bits. It consists of a 3-bit COS (Class of Service) field, a 4-bit TOS field and a 1-bit final bit. The 4 bits of the TOS field indicates the minimum delay, the maximum throughput, the highest reliability and the minimum cost respectively.

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Total length: indicates the length of the whole IP packet including the original data. This field is 16 bit long which means an IP packet can be 65535 bytes at most. Although an IP packet can be up to 65535 byte long, most data link layers segment them before transmission. Furthermore, hosts cannot receive a packet more than 576 bytes and UDP limits packets within 512 bytes. However, nowadays many applications allow IP datagram that are more than 8192 bytes to go through the links especially for applications that support NFS. Identification: identifies every datagram the host sends. The value increases with the number of datagram the host sends. Time to Live (TTL) : indicates the number of routers a packet can travel through. The value decreases one every time the packet passes a router. When the value turns to 0, the packet will be discarded. Protocol: indicates the next level protocol used in the data portion of the internet datagram. It is similar to the port number. IP protocols use protocol number to mark upper layer protocols. The protocol number of TCP is 6 and the protocol number of UDP is 17. Head checksum: calculates the checksum of the IP header to see if the header is complete. The source IP address field and the destination IP address filed point out the IP addresses of the source and the destination.



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An IP address contains a network ID, which identifies a network segment uniquely or identifies the aggregation of multiple network segments. The devices in the same network segment use the same network ID.

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An IP address also contains a host ID, which identifies a device in the network segment uniquely.

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How to distinguish the network ID and the host ID? The Internet designer classifies the IP addresses into five classes according to the size of the network, namely, class A, class B, class C, class D, and class E.

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The network ID of the IP address of class A is the first octet, and the first digit of the first octet is 0. Therefore, the number of valid bits for network address in class A address is 8–1=7. The first octet of class A address ranges from 1 to 126 (127 is reserved). For example, 10.1.1.1 and 126.2.4.78 are class A addresses. The host ID of the class A address is the last three octets, namely, the last 24 bits. The IP address of class A ranges from 1.0.0.0 to 126.255.255.255. Each class A network can have 2 24 IP addresses.

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The network ID of the class B address is the first two octets. The first digit of the first octet is 1 and the second digit is 0. Therefore, the number of valid digits of the class B network address is 16–2=14. The first octet of class B address ranges from 128 to 191. For example, 128.1.1.1 and 168.2.4.78 are class B addresses . The host ID of the class B address is the last two octets, namely, the last 16 bits. The class B address ranges from 128.0.0.0 to 191.255.255.255. Each class B network can have 2 16 IP addresses.

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The network ID of the class C address is the first three octets. The first two digits of the first octet are 11, and the third digit is 0. Therefore, the number of valid digits of class C network address is 24–3=21. The first digit of the class C address ranges from 192 to 223. For example, 192.1.1.1 and 220.2.4.78 are class C addresses. The host ID of the class C address is the last octet. The class C address range from 192.0.0.0 to 223.255.255.255. Each class C network can have 28 =256 IP addresses.

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The first three digits of the first octet of class D address is 111, and the fourth digit is 0. Therefore, the first octet of the class D address ranges from 224 to 239. The class D address is used as the multicast address. The first octet of class E address ranges from 240 to 255. It is reserved for research.

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The IP address usually used are of class A, class B and class C. The IP addresses are allocated by the International Network Information Center (InterNIC) according to the scale of the company. Basically, the class A addresses are allocated to governments, the class B addresses are allocated to medium-sized companies, and class C addresses are allocated to small-sized companies. With the fast development of the Internet and also the waste of IP addresses, the IP address is becoming insufficient.



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When planning IP addresses, usually, private IP addresses are used within the same company. Private IP addresses, reserved by the InterNIC, can be freely used by the companies. The private IP addresses cannot be used to access the Internet. The reason

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class B: 172.16.0.0-172.31.255.255

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class C: 192.168.0.0-192.168.255.255

By using the private IP addresses, the enterprises reduce the cost on buying public addresses and the IP addresses are saved.



By default 

the nature mask of class A network ：255.0.0.0 or /8



the nature mask of class B network ：255.255.0.0 or /16



the nature mask of class C network ：255.255.255.0 or /24 Confidential Information of Huawei. No Spreading Without Permission


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For IP address network without subnet, it is regarded as a single network externally. For example, all the route to address 172.16.X.X is regarded as the same direction, without consideration of third and fourth byte. This reduces the route items in the

: s e

c r ou

routing table. 

However, in the way, different subnets cannot be distinguished in the same big

s e R

network. Thus, all the hosts in the network can receive the broadcast of the big network, which reduces the network performance, and not convenient for network

g n i n

management. 

o M

For example, a class B network can contain 65000 hosts. If the user applied for the

r a e

class B address only needs 100 IP address, it is a huge waste since the addresses left cannot be used by others. Hence, a method is needed to divide this kind of network into several segment, and to manage it according to different subnets.

L e r 

From the view of address allocation, subnet is the extension of network address. The network administration can decide the size of the subnet according to the need of development of organization.



Using Subnet Mask, the network equipment could decide in the IP address which part is network part and which is host part. By using subnet, the network addresses are used more efficiently. Externally, it is still a single network; and internally, it is divided into several different subnets. Confidential Information of Huawei. No Spreading Without Permission


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Subnet mask is used to distinguish the network part and host part. In a subnet mask, the “1” represents network part, and “0” for host part. By default, the subnet mask of class A network is 255.0.0.0, the subnet mask of class B network is 255.255.0.0, and the subnet mask of class C network is 255.255.255.0. Addressing without Subnet means using nature mask, no subdivision of network segment. Class B segment 172.16.0.0 with mask 255.255.0.0 Subnet Mask Representation After learning the transform between binary and decimal number, it is easy to understand the corresponding relationship for that of IP address and network mask. For example, subnet mask is 255.255.255.240(11111111 11111111 11111111 11110000),the number of bits of network must is 8+8+8+4=28, which indicates the number of consecutive “1” in the network must is 28, i.e., the network part is of 28bit length. The subnet can be represented in another method: “/28” indicate that the first 28 bits are the network ID. Calculation of Network address As shown in the slide, the IP address and subnet mask are already known. Then, the network address is obtained from the AND operation between the IP address and the subnet mask. The AND operation is 1&1=1, 1&0=0, and 0&0=0. Therefore, the calculation of the AND operation of the example in this slide is as follows: 11000000, 10101000, 00000001, 00000001 &11111111, 11111111, 11111111, 00000000 11000000, 10101000, 00000001, 00000000 The calculation result is the network address.

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Calculation of Host Number The number of hosts is calculated through the subnet mask. First, we should know that how many 0s there are in the subnet mask. As shown in the above figure, if there are m-bit 0s, then, the number of hosts is 2m. The number of IP addresses that can be allocated to the host is 2m -2 (deducting the network address containing all 0s and the broadcast address containing all 1s).

: s e

c r ou

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

Host Number ： 2m



Valid Host Number : 2m – 2



For example,IP Address：192.168.1.100/28, /28=255.255.255.240 The binary representation of subnet mask:11111111．11111111．11111111．11110000



o M

t t h

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g n i n

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network portion is 28bits,Host portion is 4bits,The total number of host: 24 ,The valid number of host: 24 -2.  This example shows the calculation of host quantity.  The subnet mask of class A address is 255.0.0.0, namely, 24-bit host ID. The subnet mask of class B address is 255.255.0.0, namely, 16-bit host ID. The subnet mask of class C address is 255.255.255.0, namely, 8-bit host ID.  This example is a class C address. The standard subnet mask has an 8-bit host ID, and in this case, the first 4 bits of it are also used as the subnet mask. Then, the maximum number of hosts is 28-4.



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In this example, the network address is of class C: 201.222.5.0. Suppose 20 subnets are needed, and 5 hosts in very subnet. Thus, it is needed to divide the last byte into subnet part and host part.



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The bits of subnet part decide the number of subnets. In this example, because it is a class C address, there are 8 bits for subnet and hosts. And since 24<20<25 , there are 5

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bits for subnets, and the maximum subnets which could be provided are 32(2 5). And the 3 bits left are for host, and 23=8, deducting the network address and broadcast

g n i n

address in this network, which is 8-2=6. It is can meet the network requirements. 

And each network segment is as follows:

or M

eL

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201.222.5.0~201.222.5.7



201.222.5.8~201.222.5.15



201.222.5.16~201.222.5.23



………



201.222.5.232~201.222.5.239



201.222.5.240~201.222.5.247



201.222.5.248~201.222.5.255



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Upgrade IPv4 to IPv6: The Internet with IPv4 as its core has so far made great success . The shortage of IPv4 address resources directly limits the application of IP technologies on a larger scale. The development of mobile (3G) and broadband technologies gives rise to the need for more IP address . Technologies like CIDR, NAT and DHCP, though temporarily ease the shortage of IPv4 addresses, cannot solve the problem fundamentally . IETF raised the idea about the next generation Internet protocol, IPv6, in the 1990’s.Its fundamental improvement to IPv4 is the almost unlimited address space (the length of address increases from 32 bits to 128 bits). The fast expansion of the Internet is beyond the imagination of its designers. In particular, the past decade has seen a proliferation of the Internet, which has become a necessity for tens of thousands of families and individuals. It is such proliferation that leads to depletion of IP addresses. The application of new technologies deteriorates the shortage of IP addresses. As technologies develop, the PDA, wireless equipment, 3G mobile telephone and even automobile and refrigerator require a global unicast address to get access to the Internet . In addition to address shortage, demand for functions like security, QoS and easy configuration gives rise to a common ground: a new protocol to fundamentally solve all problems IPv4 is now confronted. The IP address depletion process has shown to us that we need and be able to design a new protocol in place of the current IPv4, and the new protocol should provide more than extended address space. We are now facing a good opportunity to revise the IPv4 addressing scheme.

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What is new in IPv6? Brand-new packet format IPv6 uses new header format, instead of simply extending the address in an IPv4 header to 128 bits. An IPv6 header consists of IPv6 header and extension header. The latter includes non-fundamental and optional fields. All this streamlines header processing by intermediate routers. Plenty of address An IPv6 address is 128-bit long, four times an IPv4 address. As you know, in principle there can be 232 IPv4 addresses, namely 4,294,967,296, or two addresses for every three people in the whole (based on current population). Then what does 128-bit mean? 3.4*1038! This means each people in the world can have 5.7*1028 IPv6 addresses (the actual available addresses are less but still huge). There is even a saying goes: You can allocate an IP address to every grain of sand on the earth. Brand-new address configuration As technologies develop, nodes on the Internet are no longer limited to the computer, they can be a PDA, mobile phone, terminal of any kind, and even refrigerator and TV set. This calls for easier IPv6 host address configuration .To this end, IPv6 supports Stateless Address Autoconfiguration as well as manual address configuration and Stated Address Autoconfiguration (by a special address allocation server). Stateless Address Autoconfiguration enables a host to configure IPv6 address for itself. All hosts on a link can communicate with others without human interference. Better QoS A new Flow Label field is defined in the IPv6 header. This field enables a router to identify and process packets belonging to the same flow. With this flag , a router can identify a flow without even accessing its inner packet, thus ensuring the QoS in the case of payload encryption. Built-in security IPv6 supports IPSec with extension headers like AH and ESP. This provides a standard-based solution to network security, enabling compatibility among different IPv6 solutions. Built-in mobility The Routing Header and Destination Options Header provide built-in mobility. A complete IPv6 address is expressed by IPv6 address plus prefix length . As you know, IPv4 address is in dotted decimal format plus the mask or prefix length, such as 192.168.1.1/24. An IPv6 address is 128-bit long, so the decimal expression does no apply any longer. RFC2373 defines a different text presentation. Confidential Information of Huawei. No Spreading Without Permission

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Similar to IPv4 addresses, an IPv6 address consists of prefix and ID (host ID in IPv4, interface ID in IPv6).



IPv6 prefix As the name suggests, address prefix is the digital sequence prepended to an address. Of course, it belongs to the 128 bits. This part is either a fixed value or the routing/subnet ID, similar to the network ID of an IPv4 address. The prefix is expressed as follows (similar to IPv4 CIDR): address/prefix length.



: s e

c r ou



ar 

e L e

Automatically generated in accordance with IEEE EUI-64

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



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An IPv6 address also includes an interface ID. Then how is the interface ID generated? Currently three methods are available. Generated at random by the device The device can generate an interface ID at random, which is supported by Windows XP currently. Manual configuration As the name suggests, manual configuration is to specify an interface ID manually.

IEEE EUI-64

or M







ID

A typical interface ID is 64 bits. IEEE EUI-64 defines how to generate a 64-bit interface ID based on an IEEE 48-bit MAC address. In a MAC address, c bit stands for vendor ID, d bit stands for vendor code ID, “0” bit is global/local bit, meaning global effectiveness. g specifies an individual host or a group. To convert: Change 0 to 1, and insert FFFE between c and d. The result is IPv6interface ID. This method streamlines configuration especially in the case of Stateless Address Auto configuration (to be covered later), where what you need is merely an IPv6 prefix. An obvious weakness of this method is the possibility for a malicious user to calculate the L3 IPv6 address based on the L2 MAC address.

Change 48-bit MAC address to 64-bit interface ID  

Automatically generated by the device MAC address is unique, so interface ID is unique too Confidential Information of Huawei. No Spreading Without Permission


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Hexadecimal expression . “:” separated 4-digit (16 bits) pieces . Address prefix is expressed as “/xx”. For example：2001:0410:0000:0001:0000:0000:0000:45ff/64 The 128-bit IPv6 address is divided into 16-bit pieces, each expressed by a 4-bit hexadecimal value, and separated by a ”:”. This form is called colon separated hexadecimal expression. The preferred form plus the prefix length forms a complete IPv6 address.

c r ou

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Compression form (RFC2373)  The leading zeros of an address can be omitted, and multiple groups of 16-bit of zeros can be expressed by “::”. The "::" can only appear once in an address . The prefix length is expressed by “/xx”.  For example: 2001:410:0:1::45ff/64,2001:410::1::45ff/64 is a wrong expression. The preferred form includes eight 16-bit pieces. There are many zeros in the expression that are obvious unnecessary. In order to make writing addresses containing zero bits easier, a special syntax is available to compress the zeros. According to RFC2373, "::" is used to indicate multiple groups of 16-bit of zeros, but the "::" can only appear once in an address (or the system cannot judge how many all-0 groups are omitted). Unnecessary zeros can be omitted. The address of preferred form, 2001:0410:0000:0001:0000:0000:0000:45ff can also be expressed as 2001:410:0:1::45ff,The following addresses are invalid (using “::” for several times): ::AAAA::1and3ffe::1010:2A2A::1

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According to RFC2373 (IPv6 Addressing Architecture), three expressions of IPv6 addresses are available. Preferred form, compression form and alternative form. Preferred form (RFC2373) 

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Note: You cannot compress valid zeros in a group. For example, you cannot compress FF02:30:0:0:0:0:0:5 to FF02:3::5, but to FF02:30::5.The compression form plus the prefix length is a complete IPv6 address: 2001:410:0:1::45ff/64 Alternative form (RFC2373)  In some special cases, the IPv6 address must include an IPv4 address, such as address for IPv6 tunnel compatible with IPv4.Such IPv6 address can be expressed in preferred or compression form except the IPv4 address part . The built-in IPv4 is still in dotted decimal format . The address prefix is expressed as “/xx”.  For example：0:0:0:0:0:0:166.168.1.2/64 and ::166.168.1.2/64 In some special cases, the IPv6 address must include an IPv4 address. To highlight the IPv4 address, RFC2373 defines an alternative form of IPv6 address . The alternative form is detailed in other IPv6 related trainings . An IPv6 address of this form consists of hexadecimal values and a standard presentation of IPv4 address. Two types are available.Here is an example: 0:0:0:0:0:0:192.168.1.2 or ::192.168.1.2 , 0:0:0:0:0:FFFF:192.168.1.2 or ::FFFF:192.168.1.2  The alternative form plus the prefix length is a complete IPv6 address: 0:0:0:0:0:0:192.168.1.2 / 64 or ::192.168.1.2/64 Note that RFC2373 is replaced by RFC3513, but the definitions about text presentation of addresses basically remain unchanged.



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192.168.1.1/30

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192.168.1.5/30

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Question : What’s NAT?

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Due to lack of IP address, the Network Address Translation (NAT) technology is widely applied to existing IPv4 networks, and is considered an effective (even permanent) solution to IP address shortage. However, NAT comes with certain inherent deficiencies that make it merely a temporary solution. It may prolong the lifecycle of IPv4, but cannot solve the address shortage fundamentally:  NAT breaks the point-to-point model of IP. IP is initially designed to enable connection processing only on end points (host and server). The application NAT greatly affects peer communication. In a peer communication model, a peer can serve as either a server or a client. Peers communicate with each other by sending packets directly to the other. If one peer is behind the NAT, additional processing is needed.  Need for keeping connectivity. The NAT technology requires the NAT to keep connectivity. It must remember the address and port it translates. Address and port translation all require additional processing, which decreases network performance. In addition, an organization who need to record its end users’ behaviors for security must also maintain a NAT state table.  Breaking end-to-end network security. Some encryption algorithms are used to ensure integrity of the IP header that must remain unchanged when traveling from source to destination. The source is responsible for header integrity, while the destination checks the integrity. Any change to the header on the way will cause problem to integrity check.

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Introduction to QinQ



The QinQ technology provides a cheap and easy Layer 2 (L2) virtual private network (VPN) solution. With the VLAN stacking and nesting technology, the data packets carry

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two VLAN tags at two different layers to identify different data packets. This method clears the limit of the original solution in which only one VLAN tag at one layer is used

s e R

to identify different data packets. As a result, the VLAN IDs are extended. 

The network services are becoming more complex and the number of service

g n i n

subscribers continuously increases. Hence, the original VLAN IDs no longer meet the actual demands. In addition, the Layer 3 (L3) switch is becoming mature in technology

r a e

and is more widely used. As a result, many users of intranets and small metropolitan area networks (MANs) encounter the following problems:

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The network is complex, and configuration and maintenance is difficult.



Many manufacturers' L3 switch does not support the multi-protocol label switch (MPLS) function. If the user constructs a VPN based on MPLS, the existing switch equipment has to be knocked out, which results in a severe waste of resources.

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The boards that support the MPLS function are expensive. The small-sized users cannot afford to buy them.



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The QinQ technology brings about the following benefits:

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Extends the VLAN ID resources. By VLAN stacking, the number of VLAN IDs can be increased to 4096 x 4096.



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Simplifies the network configuration and maintenance because the users and the operator can independently and flexibly plan the VLAN resources.



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Unties the users from depending on the MPLS function. As a result, the expenditure on equipment upgrade is reduced.

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Realizes a situation in which various boards that support the QinQ function are available and cheaper, compared with the boards that support the MPLS function. Extends the network service scale from the local area network (LAN) to the wide area network (WAN).



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VLAN stacking refers to a technique in which one more VLAN tag is added in front of the existing VLAN tag in a data frame structure. That is, one data frame carries two VLAN tags at two layers in VLAN stacking.

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As shown in Figure, C-VLAN indicates the customer-side VLAN; S-VLAN indicates the supplier-side VLAN.



Types of VLAN Tags



VLAN tags are used to identify customer-side packets and supplier-side packets.



IEEE 802.1ad defines two types of VLAN tags, as shown in Figure.

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Customer-side VLAN tag, which is referred to as C-VLAN.



Supplier-side VLAN tag, which is referred to as S-VLAN.

Where, the length of the data text is variable. The maximum length of the data text is related to the maximum frame length that the ports of the equipment support.



Structures of the S-VLAN and C-VLAN Tags



The 4-byte S-VLAN or C-VLAN text is divided into two subtexts: the tag protocol ID (TPID) and the tag control information (TCI).Both the TPID and TCI consist of two bytes.



TPID structure,TPID consists of two bytes to indicate the VLAN tag type. The TPID of the C-VLAN is always 0x8100; the TPID of the S-VLAN can be set.



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Networking and Application

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Learning the common QinQ application scenarios and referring to them in the case of similar scenarios help correctly configure the QinQ function.



As shown in Figure, Internet users, IPTV users, and key clients require access to the broadband network of the community where they live. They are assigned with different C-VLAN IDs for identification. A switch aggregates the services of different requirements. When the services are accessed to the supplier-side network, they are added with different S-VLAN tags for identification and indication to meet the different requirements of user access.



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You can configure the QinQ function on the OptiX NE to realize the following purposes:

eL

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The external S-VLAN ID of the department A data packet whose C-VLAN ID is100 is 30. The external S-VLAN ID of the department B data packet whose C-VLAN ID is100 is 31.

In this manner, different client services with different two-tag combinations are classified and transmitted to different destinations. A specific two-tag combination for each client clears the limit of identifying services based on only one VLAN ID to a great extent and facilitates the grooming in and between the customer- and supplier-side networks. Confidential Information of Huawei. No Spreading Without Permission


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The QinQ technology provides a cheap and easy Layer 2 (L2) virtual private network (VPN) solution. With the VLAN stacking and nesting technology, the data packets carry two VLAN tags at two different layers to identify different data packets. This method

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clears the limit of the original solution in which only one VLAN tag at one layer is used to identify different data packets. As a result, the VLAN IDs are extended. 



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Extends the VLAN ID resources

g n i n



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The QinQ technology brings about the following benefits: The users and the operator can independently and flexibly plan the VLAN resources



The expenditure on equipment upgrade is reduced



The QinQ technology provides a cheap and easy Layer 2 (L2) virtual private network (VPN) solution



Extends the network service scale from the local area network (LAN) to the wide area network (WAN)



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The Internet based on the IP technology prevailed in the middle 1990s. The IP technology, however, performs poorly in forwarding packets because of inevitable software dependence on searching routes through the longest match algorithm. As a

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result, the forwarding capability of IP technology becomes a bottleneck to the network development. 

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In the traditional IP forwarding, physical layer receives a packet from a port on the router, then sends to data link layer. Data link layer removes link layer encapsulation,

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then sends to corresponding network layer according to protocol field of the packet. The network layer will check whether the packet is sent to this device, if it is, it will

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remove network layer encapsulation, and send to its up-level protocol. If it is not, it will lookup routing table according to packet’s destination IP address, if the route is matched, the packet will be sent to data link layer of the corresponding port, after encapsulated by data link layer, it will be transmitted. If it is not matched, the packet will be discarded.

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The traditional IP forwarding adopts hop-by-hop forwarding, each router that packet passed through should implement the process (as the figure shows, RTA receives a data packet whose destination IP address is ×. ×. ×. ×, RTA will lookup routing table and forward according to matched route item, RTB, RTC will also do like this), So the efficiency is low. And all the routers need to know all routes in the entire network or default route . Besides, the traditional IP forwarding is connectionless oriented, so it is hard to deploy Qos.Confidential Information of Huawei. No Spreading Without Permission


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With the evolvement of network technologies, the Asynchronous Transfer Mode (ATM) technology comes out. It uses labels (namely, cells) of fixed length and maintains a label table that is much smaller than a routing table. Therefore, compared with the IP

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technology, the ATM technology performs much better in forwarding packets. The ATM technology, however, is difficult to popularize because of its complex protocol

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The traditional IP technology is simple and costs little in deployment. People then are eager to making a technical breakthrough to combine advantages of IP and ATM technologies. Thus, the MPLS technology comes forth. Initially, MPLS emerges to increase the forwarding rate of devices. Different from IP routing in forwarding packets, MPLS analyzes a packet header only on the network edge but not at each hop. In this manner, the time to process packets is shortened . The application specific integrated circuit (ASIC) technology is developed and the routing rate is no longer a bottleneck of the network development. As a result, MPLS does not have advantages in high-speed forwarding any more. MPLS supports multi-layer labels, and its forwarding plane is connection-oriented. Thus, MPLS is widely used in Virtual Private Network (VPN), traffic engineering (TE), and Quality of Service (QoS). MPLS works between the data link layer and the network layer in the TCP/IP protocol stack. It provides the IP layer with connection services and obtains services from the data link layer. MPLS replaces IP forwarding with label switching. A label is a short connection identifier of fixed length that is meaningful for the local end. The label is similar to the ATM virtual path identifier (VPI)/virtual channel identifier (VCI) and the Frame Relay data link connection identifier (DLCI). The label is encapsulated between the data link layer and the network layer . MPLS is not limited by any specific protocol of the data link layer and is enabled to use any Layer 2 media to transfer packets. The origin of MPLS is the Internet Protocol version 4 (IPv4). The core MPLS technology can be extended to multiple network protocols, such as the Internet Protocol version 6 (IPv6), Internet Packet Exchange (IPX), Appletalk, DECnet, and Connectionless Network Protocol (CLNP). Multiprotocol in MPLS means that the protocol supports multiple network protocols. In fact, the MPLS technology is a tunneling technology rather than a service or an application. It supports multiple protocols and services. Moreover, it can ensure the security for data transmission. Confidential Information of Huawei. No

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The typical structure of MPLS network is shown in this slide: the router and ATM switch located inside of MPLS domain are called LSR, router and ATM switch located at the edge of MPLS domain that used to connect IP network or other kinds of network are called LER . In IP network, it implements traditional IP forwarding; in MPLS domain, it implements label forwarding. The fundamental element of an MPLS network is Label Switching Router (LSR). Many LSRs on a network form an MPLS domain. LSRs that reside at the edge of an MPLS domain and connect to other networks are Label Edge Routers (LERs). LSRs within an MPLS domain are core LSRs. If an LSR connects to one or more adjacent nodes that do not run MPLS, the LSR is the LER. If all the adjacent nodes of an LSR run MPLS, the LSR is the core LSR. The transfer of packets in the MPLS domain is based on labels. When IP packets enter an MPLS network, the LER at the entrance analyzes IP packets and then adds proper labels to them. All nodes on the MPLS network forward data according to labels. When IP packets leave the MPLS network, the labels are deleted on the LER that is the exit. The path that packet passes through in MPLS domain is called Label Switch Path (LSP), this path is already confirmed and established by kinds of protocols before packet forwarding, packet will be transmitted along the specified LSP . An LSP is a unidirectional path in the same direction with the data flow. Both of LER and LSR have the ability of label forwarding, but they are located in different position, the packet processing is different. LER’s charge is to receive IP packet from IP network and insert label into the packet, then transmit it to LSR, whereas, its charge is also to receive labeled packet from LSR and remove label, transmit it to IP network; LSR’s charge is to forward according to the label.

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MPLS Forwarding－Ingress LER (RTA) When a IP packet enters MPLS domain, ingress LER (RTA) will analyze packet, determine which label to encapsulate packet according to packet characteristic (generally by prefix analysis of destination IP address), and determine to transmit to which next hop from which interface. FEC represents the same kind of packets, NHLFE contains next hop, label operation and other information. Only associating FEC with NHLFE, it can implement particular label forwarding for same kind of packets, FTN can implement this function, FTN (FECto-NHLFE) indicates the mapping for an FEC to NHLFE, if there are multiple cost-equal paths, one FEC maybe map to multiple NHLFE. MPLS Forwarding－LSR (RTB) RTB receives message with MPLS label 1024 from RTA, and forwards it according to MPLS label.first , it will find the next hop (RTC), use outgoing label to swap incoming label, and then continue forwarding. (this case is special, outgoing label and incoming label are the same.) ILM maps each incoming label to a set of NHLFE, It is used when forwarding packets that arrive as labeled packets. If there are multiple equal-cost paths, one incoming label maps to multiple NHLFE. MPLS Forwarding－LSR (RTC) Similar to RTB, when RTC receives message with label 1029, it forwards packet by label, and uses new outgoing label to swap original label, then transmits packet from outgoing interface , the next hop is RTD. MPLS Forwarding－Egress LER (RTD) Egress LSR RTD receives message with label 1039, Pops the label, lookups IP routing table and forwards it.

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Multiprotocol Label Switching (MPLS) is a technology combining the routing function of Layer 3 and the forwarding function of Layer 2. MPLS was first developed to help increase the forwarding speed. Its architecture consists of:

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It is connectionless and implemented through the current IP network.

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Forwarding plane

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Also known as data plane, it is connection-oriented and can make use of the Layer 2 network such as ATM or Frame Relay network.

MPLS uses a short label of fixed length to encapsulate packets. Data with the label is fast forwarded on the data plane. The powerful, flexible routing function of the IP network is used on the control plane to meet the demands of new applications for the

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MPLS originates from the Internet Protocol version 4 (IPv4). Its core technique can be applied to a variety of network layer protocols. These include Internet Protocol version 6 (IPv6), Internet Packet Exchange (IPX), Appletalk, DECnet, Connectionless Network Protocol (CLNP), and so on. That is what multiprotocol means.



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There are two MPLS encapsulation modes: frame mode and cell mode.  Frame encapsulation mode inserts a MPLS label header between layer 2 header and layer 3 header. Ethernet and PPP protocol adopt this mode.  ATM adopts cell mode MPLS encapsulation, VPI/VCI fields in ATM cell header are used for label switching. If there is a MPLS Header in the packet, this MPLS Header will be reserved, but not used for forwarding, and only the first cell reserves MPLS Header. A label is a short identifier of a fixed length that is only meaningful for the local end. It is used to uniquely identify an FEC to which a packet belongs. In some cases such as load balancing, an FEC can represent multiple incoming labels, but one label only represents one FEC on a device. The label is a connection identifier, similar to the ATM VPI/VCI and the Frame Relay DLCI. A label contains the following fields:  Label: indicates the value field of a label. The length is 20 bits.  Exp: indicates the bits used for extension. The length is 3 bits. Generally, this field is used for the Class of Service (CoS) that serves similarly to Ethernet 802.1p.  S: identifies the bottom of a label stack. The length is 1 bit. MPLS supports multiple labels, namely, the label nesting. When the S field is 1, it means that the label is at the bottom of the label stack.  TTL: indicates the time to live. The length is 8 bits. This field is the same as the TTL in IP packets. Labels are encapsulated between the data link layer and the network layer. Thus, labels can be supported by all protocols of the data link layer . Figure shows the position of the label in a packet and the encapsulation structure of the label.

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The protocol filed PID in layer 2 header specifies that payload starts with packet with label encapsulated or IP header. For example, in Ethernet protocol, PID=0x8847 identifies that the frame payload is a multicast MPLS packet. PID=0x8848 identifies that the frame payload is a unicast MPLS packet. PID=0x0800 identifies that the frame payload is a unicast IP packet. In PPP protocol, PID=0x8281 identifies that the frame payload is a unicast MPLS packet. PID=0x8283 identifies that the frame payload is a multicast MPLS packet.

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S bit in MPLS header indicates whether the next header is another label or a layer 3 IP header.

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Usually MPLS only allocates one label for a packet. But some advanced applications of MPLS use multiple labels. For example, MPLS VPN will use 2 layers of labels (in complex situation, it even uses 3 layers of labels), out-label is used for public network forwarding, in-label is used to indicate that which VPN the packet belongs to; MPLS TE also uses two or more labels, the outmost label is used to indicate TE tunneling, inlabel indicates the destination of packet.

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Note: The Label1, Label2, Label3 all mean 4 Bytes MPLS header in last slide, it includes 20-bit label information.

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A label stack is a set of arranged labels. An MPLS packet can carry multiple labels at the same time. The label next to the Layer 2 header is called the top label or the outer label. The label next to the Layer 3 header is called the bottom label or inner label. Theoretically, MPLS labels can be nested limitlessly.

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The label stack organizes labels according to the rule of Last-in, First-Out. The labels are processed from the top of the stack. Confidential Information of Huawei. No Spreading Without Permission


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FEC (Forwarding equivalence class) means a group of IP packets which are forwarded in the equipollence method, for example, a group of IP packets with same destination IP prefix will be allocated a unique label.

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NHLFE (Next Hop Label Forwarding Entry ) is used when forwarding a labeled packet, It contains the following information: the packet's next hop;

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the operation to perform on the packet's label stack (it contains pushing new

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label, popping label, replacing the original label with new label). It may also contain other information, such as the data link encapsulation to use when

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Label Switching Router

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A Label Switching Router (LSR) refers to devices that can swap labels and forward MPLS packets. It is also called the MPLS node. The LSR is a fundamental element on an

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LER

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An LER is the LSR that resides on the edge of an MPLS domain. When an LSR connects to one node that does not run MPLS, the LSR acts as the LER.

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The LER classifies the packets entering an MPLS domain by FECs and pushes labels into FECs. Then, the LER forwards MPLS packets based on labels. When packets leave the

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Label Switched Path

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The path that an FEC passes through in the MPLS network is called the LSP . An LSP functions similarly to virtual circuits of ATM and Frame Relay. The LSP is a unidirectional path from the ingress to the egress.

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Ingress, Transit, and Egress LSRs

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The LSP is a unidirectional path. LSRs along an LSP can be classified as follows:

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Transit LSR: indicates the middle node of an LSP. Namely, the nodes between both ends along the LSP are transits. Multiple transit LSRs may exist on an LSP . The transit LSR mainly searches routes in the label forwarding table. Then, it swaps labels to complete the forwarding of MPLS packets.

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Ingress LSR: indicates the beginning of an LSP. Only one ingress exists on an LSP . The ingress pushes a new label to the packet and encapsulates the IP packet as an MPLS packet to forward.

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Egress LSR: indicates the end node of an LSP. Only one egress exists on an LSP . The egress mainly pops labels out of MPLS packets and forwards the packets that restore the original encapsulation.

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The ingress LSR and egress LSR serve as LSRs and LERs. The transit LSR serves as the LSR.

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An LSP may have none, one, or several transit(s), but only one ingress and one egress.

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Procedure of Establishing LSPs

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Usually, MPLS allocates labels for packets and establish an LSP. Then, MPLS can forward packets.

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Labels are allocated and distributed by a downstream LSR to an upstream LSR. The downstream LSR classifies FECs according to an IP routing table and then allocates labels to specific FECs. Then, the downstream LSR notifies the upstream LSR through label advertisement protocols to set up a label forwarding table and an LSP.

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The classification of LSPs is as follows: 

Static LSP: It is set up by the administrator.

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Dynamic LSP: It is set up by the routing protocol and label distribution protocol.



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Information about the basic label operations is a part of the label forwarding table. The operations are described as follows:  Push: When an IP packet enters an MPLS domain, the ingress adds a new label to the packet between the Layer 2 header and the IP header; or, an LSR adds a new label to the top of the label stack, namely, the label nesting.  Swap: When a packet is transferred within an MPLS domain, the local node swaps the label at the top of the label stack in the MPLS packet for the label allocated by the next hop according to the label forwarding table.  Pop: When a packet leaves an MPLS domain, the label is popped out from the MPLS packet; or, the top label of the label stack is popped out at the penultimate hop on an MPLS network to decrease the number of labels in the stack. Penultimate Hop Popping In fact, the label is useless at the last hop of an MPLS domain. In this case, the feature of penultimate hop popping (PHP) is applied. On the penultimate node, the label is popped out of the packet to reduce the size of the packet that is forwarded to the last hop. Then, the last hop directly forwards the IP packet or the VPN packet. PHP is configured on the egress. In addition, the egress only allocates the following label to the PHP:  Label 3: indicates the implicit-null label. This label is not listed in the label stack. When an LSR receives an implicit-null label, the LSR pops out the label in the packet rather than uses this implicit-null label to replace the label at the top of the label stack. The egress directly forwards the packet through an IP link or according to the next layer label.

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Establishing Static LSPs

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You can allocate labels manually to set up static LSPs. The principle is that the value of the outgoing label of the upstream node is equal to the value of the incoming label of

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The availability of a static LSP makes sense only for the local node that cannot sense the entire LSP.

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On the ingress: A static LSP is set up, and the outgoing interface of the ingress is

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On the transit: A static LSP is set up, and the incoming and outgoing interfaces of the transit are enabled with MPLS. If the incoming and outgoing interfaces are Up on the physical layer and protocol layer, the static LSP is Up, regardless the existence of the ingress, egress, or other transits.

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On the egress: A static LSP is configured, the incoming interface of the egress is enabled with MPLS. If the incoming interface is Up on the physical layer and protocol layer, the static LSP is Up, regardless the existence of the ingress or the transit.

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A reachable route is required on the ingress only for setting up a static LSP, but not on the transit or egress. Confidential Information of Huawei. No Spreading Without Permission


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A static LSP is set up without label distribution protocols or exchanging control packets. Thus, the static LSP costs little and it is applicable to small-scale networks with simple and stable topology. The static LSP cannot vary with the network topology

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Static LSPs are configured by the administrator. Dynamic LSPs are set up by label

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Processing MPLS TTL

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An MPLS label has a TTL field in the length of 8 bits. The TTL field is the same as that in an IP packet header. MPLS processes the TTL to prevent loops and implement

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RFC 3443 defines two modes in which MPLS processes the TTL, that is, uniform mode

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The Hybrid MSTP equipment supports both types.

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Uniform Mode

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When IP packets enter an MPLS network, on the ingress, the IP TTL decreases by one

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one and is mapped to the IP TTL field . Namely, when an egress node pops the label, it renews the packet scheduling priority according to the EXP field in the label.



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Pipe Mode

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As shown in Figure , on the ingress, the IP TTL decreases by one and the MPLS TTL is constant. Then, MPLS TTL is processed in the standard mode. On the egress, IP TTL

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Establishing Dynamic LSPs

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Dynamic LSPs are set up automatically by the label distribution protocol. The following label distribution protocols are applicable to an MPLS network.

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Label Distribution Protocols

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Label distribution protocols are MPLS control protocols, namely, signaling protocols. They are used to classify FECs, distribute labels, and create and maintain LSPs.

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MPLS utilizes multiple label distribution protocols, such as Label Distribution Protocol (LDP), Resource Reservation Protocol Traffic Engineering (RSVP-TE), and Multiprotocol

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Border Gateway Protocol (MP-BGP).

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LDP

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The Label Distribution Protocol (LDP) is specially defined for distributing labels. When LDP sets up an LSP in hop-by-hop mode, LDP identifies the next hop along the LSP according to the routing forwarding table on each LSR. Information contained in the routing forwarding table is collected by IGP and BGP. LDP is not directly associated with routing protocols, but indirectly uses routing information.

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LDP is not the only label distribution protocol. BGP and RSVP can also be extended to distribute MPLS labels.

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RSVP-TE

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The Resource Reservation Protocol (RSVP) is designed for the integrated service module and is used to reserve resources on nodes along a path. RSVP works on the transport layer and does not transmit application data. RSVP is a network control protocol, similar to the Internet Control Message Protocol (ICMP).

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RSVP is extended to support the setting up of a Constraint-based Routed LSP (CR-LSP). The extended RSVP is called the RSVP-TE signaling protocol. It is used to set up TE tunnels.

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Different from LDP LSPs, RSVP-TE tunnels are characteristic as follows: 

Bandwidth reservation requests

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Bandwidth constraint

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Link colors

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Explicit paths

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MP-BGP

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The Multiprotocol Extensions for BGP (MP-BGP) is an extended protocol of BGP. MP-BGP imports the community attribute. MP-BGP supports label distribution for routes over MPLS VPN and the Inter-AS VPN. Confidential Information of Huawei. No Spreading Without Permission


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However, with the development of ASIC technology, routing lookup speed is not bottleneck of network development any more. Improving forwarding speed is no longer the obvious advantage of MPLS.

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MPLS integrates the advantage of the two forwarding technologies, powerful layer 3 routing function of IP network and high efficiency forwarding mechanism of traditional layer 2 network, its forwarding plane adopts connection oriented, it is very similar to layer 2 network forwarding method in existence.

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It makes MPLS easy to implement seamless combination of IP and ATM, frame relay and other layer 2 network, and provide better solution for TE (Traffic Engineering),

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VPN based on MPLS can combine different embranchment of private network, form a uniform network, VPN based on MPLS also supports communication control between different VPN. As the figure shows, CE is user edge device; PE is service provider edge router, which is located in backbone network. P is backbone router in the service provider network, it does not directly connect with CE. VPN data is transmitted along LSP (label switch path) encapsulated with MPLS label.



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This figure shows the networking topology of MPLS L2 VPN and MPLS L3 VPN.

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Both MPLS L2 VPN and L3 VPN model contain the following parts:

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CE is Customer Edge. It indicates an edge device in the customer network, which has one or more interfaces directly connected to the service provider network. A CE can be a router, a switch or a host. Mostly, the CE cannot "sense" the existence of the VPN, and does not need to support MPLS.

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PE is Provider Edge. It indicates an edge device of the provider network, which is directly connected to the CE. In the MPLS network, the PE device performs all the VPN-related processing.

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P is Provider. It indicates a backbone device in the provider network, which is not directly connected to the CE. The P device need only provide basic MPLS forwarding capability. Site indicates a group of IP systems. Sites have IP connectivity between each other and this connectivity is independent of the service provider network. A site is connected to the provider network through the CE. A site may contain many CEs, but a CE belongs only to a single site.

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Both MPLS L2 VPN and MPLS L3 VPN Services are offered from the edge of a network.  

MPLS L3 VPN passes IP traffic over IP Backbone.

MPLS L2 VPN passes Ethernet, ATM, Frame Relay, PPP, HDLC traffic over IP Backbone. Confidential Information of Huawei. No Spreading Without Permission


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This table lists some major difference between MPLS Layer 3 VPN and MPLS L2 VPN.

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This figure shows a typical Metropolitan Ethernet Network. In this network, Triple Player service (HIS service, VOIP Service and BTV Service ) and Enterprise Interconnection are provided to customers.

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HIS Service, VOIP service, BTV Service are transmitted over separate MPLS L2 VPNs.

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The branch offices of the enterprise communicate with each other through MPLS L2 VPN.

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The speed of traditional IP forwarding is low, and all the routers should maintain the routes of the entire network, so it is hard to deploy QoS.

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MPLS completes data forwarding by label.

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MPLS VPN，MPLS QoS，MPLS TE.

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the development of the IP data network, the scalability, upgrade, and

compatible interworking of the IP network become powerful. The traditional network is poor in upgrading, scaling, and interworking. It is confined by the transmission

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mode and service type, and the newly established network is difficult to share and manage. Therefore, in upgrading and expanding the traditional network, you must

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decide to establish a repetitious network or fully utilize the current or public network resources. PWE3 is a solution to combine the traditional network and the current

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packet-based network. PWE3

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is a technology that bears Layer 2 services. PWE3 emulates the basic behaviors

and characteristics of the services such as Asynchronous Transfer Mode (ATM) , Frame Relay (FR) , Ethernet, low-speed Time Division Multiplex (TDM) circuit, and Synchronous Optical Network (SONET) or Synchronous Digital Hierarchy (SDH) in a PSN.

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PWE3 technology can interconnect the traditional network and the PSN to share the resources and expand the network. PWE3 is an extension to the Martini protocol. PWE3 extends new signaling, reduces the cost of signaling, prescribes the inter-AS multi-hop mode, and makes the networking more flexible.



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Functions of PW

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Carry the encapsulated packets to the transmit tunnel.



Set up PW at the tunnel end, including the exchanging and distribution of PW labels.

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Encapsulate the emulated service from the logical or physical port on the PE side.

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Perform the traffic monitoring in the ingress direction and traffic shaping in the egress direction. Manage signalling, timing and sequence at the PW edge. Manage the status specified by the service and alarms.



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PWE3: pseudo-wire emulation edge to edge. It is an end-to-end technology that bears Layer 2 services. PWE3 is an extension to the VPWS, especially the Martini VPWS.

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In the PWE3 network reference model, a PW connects two provider edges (PEs), and an attachment circuit (AC) connects a PE device and a customer edge (CE) device.



: s e

One or more PWs are created between PE1 and PE2 based on the service access

c r ou

requirements at the CEs. Several PWs can be carried in one or more PSN tunnels. In this manner, native services can be transmitted over a PSN.

s e R



PWE3 Basic Working Procedure



The following takes the flow direction of Virtual Private Network (VPN) packets from

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CE2 to CE4 as an example to show how PWE3 works:

ar 

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Le





CE2 sends the service flow to be Emulated to PE1 through an AC. After PE1 receives the packets, the forwarder selects a PW for forwarding the packets. PE1 generates double MPLS labels according to the forwarding entry of the PW (the private network label is used to identify the PW; the public network label is used to forward packets to PE2 through the tunnel).



After emulated service packets arrive at PE2 through the public network tunnel, the system removes the label.



The forwarder of PE2 selects an AC for forwarding the original service flow to CE4. Confidential Information of Huawei. No Spreading Without Permission


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AC: attachment circuit. It is the physical or virtual circuit that connects a CE to a PE. If the physical AC and the virtual AC adopt the same technology such as ATM, Ethernet, or FR, PWs can provide homogeneity transmission; otherwise, PWs provide heterogeneity transmission.



Forwarder : A PE sub-system that selects a PW to transmit the payload received on the AC.



Tunnel : A mechanism to transparently bear the information on the network. It is used to bear PWs. A tunnel can bear multiple PWs. In most cases, a tunnel is an MPLS tunnel. The tunnel is a channel that directly connects a local PE to a peer PE. In the tunnel, the data is transmitted transparently between PEs. PSN tunnels are available in several types, but the Hybrid MSTP equipment supports only MPLS tunnels. In this document, PWE3 is generally based on the MPLS tunnel (LSP), unless otherwise specified.

: s e

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

Encapsulation : The packets transmitted on PWs use the standard PW encapsulation type and technology. The RFC 4446 defines multiple encapsulation types of PWE3 packets on PWs.



PW signaling : The basis on which PWE3 is implemented. It is used for creating and maintaining PWs. Currently, the primary PW signaling is LDP.

r a e

or M

eL 

PW: pseudo wire . It is a mechanism that carries the essential elements of an emulated circuit between PEs over a PSN. The Hybrid MSTP equipment supports only static PWs.



CE: Customer Edge . It is a device that originates or terminates a service. The CE cannot be aware whether an emulated service or a local service is in use.



PE: Provider Edge.It is a device that provides PWE3 to a CE. It is usually the edge router that is connected to a CE on a backbone network. A PE is responsible for processing the VPN service. A PE performs the mapping and forwarding of the packets from the private network to the publicnetwork tunnels and that in the reverse order. 





U-PE: ultimate PE. It is an edge device that is directly connected to a user edge device on a backbone network. S-PE: switching PE. It is a device that is responsible for PW switching and PW label forwarding within a backbone network.

CW: control word. A control word is a 4-byte encapsulated packet header. It is used to transmit packets in an MPLS PSN.



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PWs can be classified into the following types:

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According to the implementation scheme, PWs can be classified into Static PWs and Dynamic PWs.

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According to the networking type, PWs can be classified into Single-Hop PWs and Multi-Hop PWs.

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

Static PWs specify the parameters through command rather than negotiate parameters by using signaling. Data is transmitted between PEs through tunnels.



Dynamic PWs are PWs that are set up through signaling. U-PEs switch VC labels through LDP and bind the corresponding CE through the virtual circuit (VC) ID. After

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the tunnel that connects two PEs is set up and the switching and binding of labels are complete, a VC is set up if the AC of these two PEs are Up.

o M

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The single-hop PW indicates that only one PW exists between U-PEs. The label switching at the PW label level is not needed.



The multi-hop PW indicates that multiple PWs exist between U-PEs, The forwarding mechanisms of U-PEs in multi-hop PWs and in single-hop PWs are the same. The only difference is the multi-hop PW requires to switch labels at the PW label level on the SPE.



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The single-hop PW indicates that only one PW exists between U-PEs. The label switching at the PW label level is not needed. The figure shows the networking of single-hop PWE3 and the encapsulation of packets.

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To carry out multi-hop PWs, the S-PE needs to connect the single-hop PWs at both endpoints of the PW and switch the labels at the PW level on the S-PE.



: s e

PWs can be switched in the following modes:

c r ou

Dynamic-to-dynamic: indicates that the PWs at both ends of the S-PE are set up through signaling. In dynamic-to-dynamic PWs, the remote label is sent



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from two neighboring endpoints (U-PE or S-PE) through signaling to this S-PE. The CW and the VCCV are sent to this S-PE through signaling by two U-PEs.

g n i n



ar 

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Static-to-static: indicates that PWs on both sides of the S-PE are static PWs. Dynamic-and-static: indicates that the PW on one side of the S-PE is set up through signaling, and the PW on the other side of the S-PE is set up through static configurations.



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The ETH PWE3 technology emulates the basic behaviors and characteristics of Ethernet services on a packet switched network (PSN) by using the PWE3 mechanism, so that the Ethernet services can be transmitted on a PSN.

: s e

c r ou



The outer label is used to identify a PSN tunnel; the inner label is used to identify a PW.



The tunnel label can be distributed by signaling protocol (Dynamic tunnel . It refers to

s e R

an LSP established by running the label distribution protocol (LDP).) or configured manually(Static tunnel . It refers to an LSP for which a static label is configured by

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using the management plane.). The Hybrid MSTP equipment supports static tunnels.

o M

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

The PW label can be distributed by signaling protocol or configured manually.



CW is optional. If strict sequence is required, CW should be used.

L e r



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In terms of OptiX Hybrid MSTP equipment , the Control Word parameter specifies the PW control word usage policy.



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The control word is the 4-byte encapsulation packet header. The control word is used

c r ou

to identify the packet sequence or function as stuffing bits. 

The following describes the meaning of each field in the CW: 



g n i n

r a e 

o M

L e r

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The first four bits must be 0, which indicates that the data is the PW data. The packet must be ignored by the PE that receives the packet. Reserved: It is of 12 bits. It is the reserved field and is often set to 0. Sequence Number: It is of 16 bits. It is used to guarantee the packet order. This field is optional. If the Sequence Number is 0, it means the packet order check is disabled.



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The TDM PWE3 technology emulates the basic behaviors and characteristics of TDM services on a packet switched network (PSN) by using the PWE3 mechanism, so that the emulated TDM services can be transmitted on a PSN.

: s e

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

TDM PWE3 services are also called CES services carried by PWE3. In this document, all the CES services are carried by PWE3.



TDM: Time Division Multiplex 



s e R

Transmission channel is divided into different time slots.

g n i n

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Each time slot can be used to transmit service for different users.

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E1: A type of TDM service . Transmission resource divided into 32 time slots . One time slot transmit 8 bits each time.8000 E1 frames will be transmitted per-second . So bandwidth for E1 transmission is :

L e r

32(time slots/frame)*8(bits/time slot)*8000(frames/s)=2048000(bits/s)=2.048(Mbps)=32*64(Kbps) 

Unframed E1 



Using all the 31 time slots as a whole to transmit user data.So, the total bandwidth for one unframed E1 connection is 2.048Mbps, just like the bandwidth provided by a serial interface.

Framed E1 

Time slot 0 used for signaling or other purpose . Time slot 1-31 can be used for transmit service data for different users. Confidential Information of Huawei. No Spreading Without Permission


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Elements of TDM emulation service

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To use a PW to emulate the transmission of TDM service over a PSN, the following elements must be carried to the other end of the PW : TDM data , Frame format of

: s e

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TDM data , TDM alarm and signaling at the AC side , Synchronous timing information of TDM. 

s e R

To implement TDM circuit emulation, TDM data is encapsulated with a special circuit emulation packet header, which carries frame format, alarm, signaling and

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synchronous timing of the TDM data. The encapsulated packets are called PW packets, which are carried by a protocol such as IP, MPLS or L2TP to traverse the PSN. After

r a e

arrival at the egress of the PW tunnel, they are decapsulated to reconstruct data streams of TDM CS service.

o M

L e r 

OptiX Hybrid MSTP equipment supports TDM E1 PWE3 , namely CES(Circuit Emulation Service) E1.



As shown in Figure , CES service between BTS and BSC is transfered by Hybrid MSTP equipment.BTS uses E1 interface which is connected to PE. BSC uses channelized STM1 interface which is connected to PE.



Structure Agnostic TDM over Packet Switched Network (SAToP) and Circuit Emulation Service over Packet Switched Network (CESoPSN) are two methods for encapsulating TDM serial bit streams as pseudo wires. Confidential Information of Huawei. No Spreading Without Permission


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In the SAToP mode:

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The equipment regards TDM signals as constant rate bit flows, instead of sensing structures in the TDM signals. The entire bandwidth of TDM signals is emulated.

: s e



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The overhead and payload in the TDM signal are transparently transmitted.



SAToP provides the emulation and transport functions for unchannelized TDM services. That is, it addresses only structure-agnostic transport. Therefore, SAToP can meet the transport needs when a user needs services based on E1s.



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SAToP segments and encapsulates TDM services as serial bit streams, and then transmits the bit streams in PW tunnels. Although it disregards the TDM frame structure, it supports transmission of synchronous information.



MPLS labels include tunnel labels and PW labels, which are used to identify tunnels and PWs respectively. The format of the tunnel label is the same as that of the PW label.



Control Word: optional, can choose use CW or not, if not, CW header is not required.



RTP Header/ Time Stamp/ SSRC Identifier: if RTP used, these encapsulations are required; if not, not required.



We can encapsulate one E1 frame into one PW encapsulation, or we can encapsulate more E1 frames into one PW header.

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If one E1 frame encapsulated into one PW header, more bandwidth will be used but the encapsulation time is short. If more E1 frames encapsulated into one PW header, can improve the bandwidth efficiency but need more time to encapsulate all the frames. Confidential Information of Huawei. No Spreading Without Permission


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In the CESoPSN mode:  The MSTP equipment senses frame structures, frame alignment modes and timeslots in the TDM circuit.  The MSTP equipment processes the overhead and extracts the payload in TDM frames. Then, the MSTP equipment delivers the timeslot of each channel to the packet payload according to certain sequence. As a result, the service in each channel in the packet is fixed and visible.  Each Ethernet frame that carries the CES service loads TDM frames of a fixed number.  CESoPSN provides the emulation and transport functions for channelized TDM services. That is, it identifies the TDM frame format and signaling in the frame. Therefore, CESoPSN can meet the transport needs when a user needs services based on timeslots.  With the frame format of the TDM service identified, CESoPSN does not transmit idle timeslot channels; instead, CESoPSN extracts only the usable timeslots from the service flow and then encapsulates these timeslots as PW packets for transmission. MPLS labels include tunnel labels and PW labels, which are used to identify tunnels and PWs respectively. The format of the tunnel label is the same as that of the PW label. Control Word: optional, can choose use CW or not, if not, CW header is not required. RTP Header/ Time Stamp/ SSRC Identifier: if RTP used, these encapsulations are required; if not, not required. The CESoPSN different from SAToP is:  The CESoPSN protocol can identify frame structure of TDM service. It may not transmit idle timeslot channels, but only extracts useful timeslots of CE devices from the E1 traffic stream and then encapsulates them into PW packets for transmission.  For example: only time slot 1-5 have data, all the other time slots are idle, CESoPSN can choose only transmit time slot 1-5’s data to another PE, the opposite PE can reconstruct the original E1 frame, and then send it to appropriate CE.  NOTE: CESoPSN does not support the automatic detection of idle timeslots. Therefore, idle timeslots must be manually specified.

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  



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Data Jitter Buffer

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After CES packets are transmitted over a PSN, the intervals between packet arrivals may be different and the packets may be misordered. To ensure that the TDM bit streams can be reconstructed on the egress PE, a jitter buffer is required to smooth the intervals between packet arrivals and to reorder the misordered packets.The data jitter buffer works as follows:

: s e





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The data jitter buffer enables the packets to enter the queue in the order that the packets arrive at the interface. At the same time, data jitter buffer enables the packets to leave the queue in the order that the packets enter the queue.

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When the packets are received with consecutive sequence numbers, the write pointer writes data into the queue, beginning at the tail of the queue; the read pointer reads data from the queue, beginning at the head of the queue.

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

When the received packets are misordered, the read pointer automatically accommodates to reading packets in the correct order.



The size of the data jitter buffer can be set as required. A low-capacity jitter buffer easily overflows, and as a result data may be lost at different degrees; a high-capacity jitter buffer can absorb jitters resulting from larger packet transmission intervals on the network, but a large delay may be generated when the TDM bit streams are reconstructed. Therefore, during service deployment, you need to properly configure the data jitter buffer based on the actual network delay and jitter conditions.



CES Alarm Transparent Transmission



The Hybrid MSTP equipment uses the L/M and R fields in the control word to transparently transmit alarms.CES alarm transparent transmission involves transmitting local CES alarms to the remote end, and inserting corresponding alarms to notify the remote end of faults in the local end. Depending on the position where the alarm is generated, CES alarm transparent transmission can be between AC sides, and from the NNI side to the AC side. Confidential Information of Huawei. No Spreading Without Permission


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Clock Recovery Schemes of TDM PWE3

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When clocks need to be transmitted with CES services, you can adopt CES retiming or CES adaptive clock recovery (ACR) as required.



CES Retiming CES retiming is an approach to reduce signal jitter after CES services traverse a transmission network. It combines the timing reference signal and CES service signal for transmission. Therefore, the transmitted CES service signal carries the timing information that is synchronized with the timing reference signal. CES retiming is applicable when the following conditions are met:



: s e

c r ou

s e R



All the clocks on the PSN are synchronous.



All the clocks on the PSN are synchronized with the clock of the incoming service.

g n i n

CES ACR CES ACR is a technology wherein the CES service is used to restore the clock of the source end in an adaptive manner. The sink end recovers the clock based on the packet received on its NNI side.

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All the clocks on the PSN are not synchronous. All the clocks on the PSN are synchronous, but the clocks on the PSN are not synchronized with the clock of the incoming service.



QoS of TDM PWE3



The QoS of TDM services features low delay, low jitter, and fixed bandwidth. Therefore, a high enough per-hop behavior (PHB) level needs to be assigned to CES packets.



The Hybrid MSTP equipment performs QoS for TDM PWE3 packets as follows.



Ingress node



The PHB service class of a TDM PWE3 packet can be manually specified (the PHB service class is set to EF, by default). When a packet leaves an ingress node, the EXP value of the packet is determined according to the mapping (between PHB service classes and EXP values) defined by the DiffServ domain of the egress port.



Transit node



When a packet enters a transit node, the PHB service class of the packet is determined according to the mapping (between EXP values and PHB service classes) defined by the DiffServ domain of the ingress port. When a packet leaves a transit node, the EXP value of the packet is determined according to the mapping (between PHB service classes and EXP values) defined by the DiffServ domain of the egress port.



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The ATM PWE3 technology emulates the basic behaviors and characteristics of ATM services on a packet switched network (PSN) by using the PWE3 mechanism, so that the emulated ATM services can be transmitted on a PSN.

: s e

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

The outer label is used to identify a PSN tunnel; the inner label is used to identify a PW.



ATM transparent cell transport bears the following services though the PSN:

g n i n





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The PW payload is the ATM cell.



The PW payload is the AAL5 SDU/PDU.

ATM transparent cell transport can be used to move the original ATM network through a PSN, with no new ATM device and no change of ATM CE configuration.

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ATM CEs regard ATM transparent cell transport as a TDM leased line to interconnect ATM networks by transparently transporting cells through the PSN.

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VCC cell transport

Virtual circuit connection. It is a basic unit in an ATM network.



It is applicable to transmit various ATM network services.

It is applicable for transmission of various ATM network services. If users have multiple service connections of the same destination, the VPC cell is a better

g n i n

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Virtual path connection. It is a group of VCCs with the same destination.

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VPC cell transport

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solution compared with the VCC cell. VPC cell transport is swifter than VCC cell transport and is easy to manage and configure.

One-to-one (1-to-1) 

A VCC or VPC is mapped to one PW, supports all the AAL types.



The VPI/VCI is not encapsulated.

N-to-one (N-to-1) 

Multiple VCCs or VPCs are mapped to one PW.



N >= 1. Supports all the AAL types.



The VPI/VCI is encapsulated.



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The first four bits must be 0, which indicates that the data is the PW data. The packet must be ignored by the PE that receives the packet.

g n i n

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

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The following describes the meaning of each field in the CW: 

o M

// : p

The CW, which is optional, is inserted before the ATM payload. If the MPLS PSN supports the equal-cost multiple path (ECMP), the packets may not reach the destination in the sending order. The Sequence Number field in the CW can be used to restore the correct order of the packets. If the MPLS PSN does not support the ECMP, or the network has no strict requirement for the packet order, the CW is optional.

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Flags: It is of four bits. In some cases, the network strips off the Layer 2 header at the ingress and re-adds the header at the egress. Res: It is of two bits. It is the reserved field and is often set to 0. Length: It is of six bits. The Length field is not used in N-to-1 cell transport mode. It is set to 0. Sequence Number: It is of 16 bits. It is used to guarantee the packet order. This field is optional. If the Sequence Number is 0, it means the packet order check is disabled.

An ATM Service Payload is of 52 bytes: 4-byte ATM Header and 48-byte ATM Cell Payload. A common ATM Cell is of 53 bytes. Compared with the common ATM cell, the ATM Service Payload discards a 1-byte Header Error Check (HEC) contained in the common ATM header, that is, 53 -1 = 52 bytes. Confidential Information of Huawei. No Spreading Without Permission


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The CW, which is optional, is inserted before the Pseudo wire Header. The ATM Specific Header is inserted before the ATM Cell Payload.



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The following describes the meaning of each field in the ATM Specific Header:

c r ou

M: It is of one bit. It indicates the transmission mode. That is, a packet contains an ATM cell or a frame payload. The value of 0 indicates that the packet



s e R

contains an ATM cell; the value of 1 indicates that the packet contains a frame payload.

g n i n

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

V: It refers to the VCI flag, which is of one bit. It indicates whether a packet contains the VCI field or not. The value of 0 indicates that the packet does not

contain the VCI; the value of 1 indicates that the packet contains the VCI. The VCC is an ATM connection that is switched by the VCI value in the ATM cell header. Therefore, the VCI is not needed for a VCC. Resvd: It refers to the reserved field, which is of two bits. This field is set to 0 when it is transmitted and is ignored when it is received.



The number of ATM cells to be encapsulated is negotiated between the ingress device and the egress device. Each encapsulated ATM cell has the 1-byte ATM Specific Header. Therefore, the ATM cell information of 53 bytes can be regarded as being encapsulated in 49 bytes.



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The CW, which is mandatory, is inserted before the Pseudowire Header. The ATM Specific Header is inserted before the ATM Cell Payload.



For a common ATM VPC, the egress PE cannot change the VCI field in a packet. In VPC cell transport, the egress PE can set a VCI value that is different from the VCI value on the ingress. The VCI set by the egress PE is determined only by the PW Header.



The following describes the meaning of each field in the ATM Specific Header:

: s e

c r ou

g n i n



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or M

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M: It is of one bit. It indicates the transmission mode. That is, a packet contains an ATM cell or a frame payload. The value of 0 indicates that the packet contains an ATM cell; the value of 1 indicates that the packet contains a frame payload. V: It refers to the VCI flag, which is of one bit. It indicates whether a packet contains the VCI field or not. The value of 0 indicates that the packet does not contain the VCI; the value of 1 indicates that the packet contains the VCI. The VPC is an ATM connection that is switched by the VPI value in the ATM cell header. Therefore, the VCI is needed for a VPC, and is transmitted in each cell. VCI: It is of 16 bits. This filed indicates that VCI value after the ATM cell is encapsulated.

The number of ATM cells to be encapsulated is negotiated between the ingress device and the egress device. Each encapsulated ATM cell has the 1-byte ATM Specific Header. Therefore, the ATM cell information of 53 bytes can be regarded as being encapsulated in 51 bytes. Confidential Information of Huawei. No Spreading Without Permission


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Number of ATM Cells Encapsulated in PWE3 Packets

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The number of ATM cells encapsulated in PWE3 packets is determined by the parameters Maximum Number of Concatenated Cells and Loading Time.



The number of ATM cells in a ATM service is determined by the parameters Maximum Number of Concatenated Cells and ATM Cell Concatenation Waiting Time. 



: s e

c r ou

When Maximum Number of Concatenated Cells is set to 1, each PWE3 packet contains only one ATM cell. Specifically, an ATM cell is directly encapsulated into a PWE3 packet after the PE receives an ATM cell from the AC.

s e R

When Maximum Number of Concatenated Cells is set to a value greater than 1, the PE uses the timer ATM Cell Concatenation Waiting Time. If the PE receives the maximum number of ATM cells from the AC before the timer expires, the PE encapsulates all the received ATM cells into a PWE3 packet and resets the timer. If the timer expires, the PE encapsulates all the received ATM cells into a PWE3 packet and resets the timer, even if the maximum number of ATM cells is not reached.

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QoS of ATM PWE3



The QoS requirements depend on the category of the ATM service. As such, set the PHB service level of an ATM PWE3 packet based on the category of the emulated ATM service to ensure specific QoS objectives.



Specify an appropriate PHB service level for an ATM service based on its category. The following table provides the default mapping relationships between ATM service categories and PHB service levels.



The OptiX OSN equipments perform QoS for ATM PWE3 packets as follows.



Ingress node The PHB service class of an ATM PWE3 packet can be manually specified. When a packet leaves an ingress node, the EXP value of the packet is determined according to the mapping (between PHB service classes and EXP values) defined by the DiffServ domain of the egress port.



Transit node When a packet enters a transit node, the PHB service class of the packet is determined according to the mapping (between EXP values and PHB service classes) defined by the DiffServ domain of the ingress port. When a packet leaves a transit node, the EXP value of the packet is determined according to the mapping (between PHB service classes and EXP values) defined by the DiffServ domain of the egress port.



P-98

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P-99

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The MSTP products supports various Ethernet services and provides ideal L2VPN solutions.



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A virtual private network (VPN) is a private network constructed on the basis of the

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public network. The L2VPN is the VPN based on technologies of the link layer. The VPN constructed on the public network can provide the same security, reliability and

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manageability as the existing private networks.

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

Service providers can provide the VPN value-added service for enterprises to

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

fully use the existing network resources and to increase the service volume. In addition, service providers can consolidate long-term partnership with

enterprises. For VPN users, the cost to lease the network is saved. The flexibility of the VPN networking makes the network management easier for enterprises. As the network security and encryption technology develops, the private data can be transmitted over the public network with security.



For the MSTP products, the Ethernet service has the following forms. 

Point-to-point service: E-Line service



Multipoint-to-multipoint service: E-LAN service



Multipoint-to-point converging service: E-Aggr service Confidential Information of Huawei. No Spreading Without Permission


P-100

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Company A and Company B have departments in City 1 and City 2, which need to communicate with each other respectively. The communication of Company A should be isolated from that of Company B. For such an application, the E-Line service carried

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by the PW should be created.

Create two PWs carrying the services of Company A and Company B



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respectively.

The two PWs can use one tunnel, and share bandwidth of the same tunnel.

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P-101

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The three user side networks respectively access the carrier networks through the PE. Each user side network has its own VLAN tag. The user side networks require access between each other. The user side networks can communicate with each other

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through the configuration of the E-LAN service. 

On each PE node, the accessed data is forwarded through the target MAC address or

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target MAC address + VLAN. At the network side, the data is transparently transmitted to the opposite PE equipment through the created MPLS tunnel. 

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In this case, the entire transport network, which exchanges different data at the user sides, equals a Layer 2 switch. In other words, the transport network is transparent to

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the user network.

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P-102

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Node B connected to NE1 and Node B connected to NE2 need communicate with the RNC connected to NE3. In this case, NE1 and NE2 can aggregate the services accessed from Node B to two MPLS tunnels respectively. The two MPLS tunnel then transports

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the services to NE3, which then aggregates the services to the RNC. All services of Node B have VLAN, whose value is 100. 

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Node B is connected to the equipment through the FE interface. RNC is connected to the equipment through the GE interface. The NEs are connected through the STM-4

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POS interfaces for networking.

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P-103

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Between BTS and BSC, the CES service is transported through the MSTP equipment. A CES service is available between BTS and BSC that are connected to PE1. Two CES services are available between BTS and BSC that are connected to PE2.

: s e

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

BTS1 uses one E1 connection connected to PE1, BTS2 uses two E1 connections connected to PE2. PE3 uses one channelized STM-1 connection connected to BSC.



So, we need create one PW between PE1 and PE3, and two PWs between PE2 and PE3.

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P-104

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In N-to-1 VPC ATM cell transport, a PW bears cells of multiple ATM VPCs. This mode supports all the AAL types. The tunnel packets carry the VPI/VCI value.



: s e

In this mode, multiple VPs can be set up between a PE and a CE. The data transmission

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on VPs is independent of each other. 

In N-to-1 VPC ATM cell transport, multiple VPs of an ATM sub-interface can be

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mapped to a PW. Multiple VPs of different ATM sub-interfaces cannot be mapped to a PW. In addition, multiple VPs of different service boards cannot be mapped to a PW. 

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N-to-1 VPC ATM cell transport has two types: remote N-to-1 VPC ATM cell transport and local N-to-1 VPC ATM cell transport.

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

Remote N-to-1 VPC ATM cell transport 

ATM cells are transparently transmitted across the entire PSN and each PW bears cells of multiple ATM VPCs , as shown in Figure .



Local N-to-1 VPC ATM cell transport. 

ATM cells are forwarded through the PE rather than transparently transmitted across the entire PSN.



P-105

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In 1-to-1 VCC ATM cell transport, a PW bears cells of an ATM VCC. This mode supports all the AAL types. The tunnel packets do not carry the VPI/VCI value.



: s e

In this mode, the VPI/VCI switching is supported without any switching configuration

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on the PE because the MPLS PW is considered as an ATM switch. 

1-to-1 VCC ATM cell transport has two types: remote 1-to-1 VCC ATM cell transport

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and local 1-to-1 VCC ATM cell transport.

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Remote 1-to-1 VCC ATM cell transport

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



ATM cells are transparently transmitted across the entire PSN and each PW bears cells of only one ATM VCC , as shown in Figure .

Local 1-to-1 VCC ATM cell transport. 

ATM cells are forwarded through the PE rather than transparently transmitted across the entire PSN.



P-106

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PWE3 is a technology that bears Layer 2 services. PWE3 emulates the basic behaviors and characteristics of the services such as ATM , Frame Relay (FR) , Ethernet, lowspeed TDM circuit, and SONET or SDH in a PSN.



: s e

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List the difference between SAToP and CESoPSN. In the SAToP mode:





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The equipment regards TDM signals as constant rate bit flows, instead of sensing structures in the TDM signals. The entire bandwidth of TDM

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signals is emulated.

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Le

ar 



The overhead and payload in the TDM signal are transparently transmitted.

In the CESoPSN mode: 



The MSTP equipment senses frame structures, frame alignment modes and timeslots in the TDM circuit. The MSTP equipment processes the overhead and extracts the payload in TDM frames. Then, the MSTP equipment delivers the timeslot of each channel to the packet payload according to certain sequence. As a result, the service in each channel in the packet is fixed and visible.



Typical applications of PWE3 have the following types：Ethernet Service to PWE3,TDM E1 Service to PWE3 and ATM Service to PWE3. Confidential Information of Huawei. No Spreading Without Permission


P-107

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P-108

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

VPN ：Virtual Private Network



LDP ：Label Distribution Protocol



PDU ： Protocol Data Unit



STB ： Set Top Box



HG ：Home Gate



DSLAM ：Digital Subscriber Line Access Multiplexer



BRAS ：Broadband Remote Access Server



ISP ：Internet Service Provider



VoIP ：Voice over IP



HSI ：High Speed Internet



BTV ：Broadband TV



BTS：Base Transceiver Station



BSC：Base Station Controller



RNC： Radio Network Controller



CIDR：Classless Inter-Domain Routing



DHCP：Dynamic Host Configuration Protocol

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P-109

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OptiX SDH Equipment Hardware

P-1

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Content

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1. Product Introduction ....................................................................................Page 3

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2. Cabinet, Sub-rack .........................................................................................Page 6 3. Boards ...................................................................................................... Page 16 4. Common Network Elements and Configuration ......................................... Page 52 5. Features .....................................................................................................Page 57

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P-2

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References

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

OptiX OSN 3500 Hardware Description manual



OptiX OSN 3500 Product Description manual

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P-3

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P-4

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

OptiX OSN 1500/2500 mainly used in Optical convergence or access switching system.



OptiX OSN 3500 mainly used in Optical convergence and core switching system.



OptiX OSN 7500 mainly used in Optical core switching system.

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P-5

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Tributary unit (TU): access low rate signal (PDH, Ethernet, ATM, and so on) & process it.

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Line unit (LU): access optical high rate signal (STM-1/4/16/64 SDH signal) & process it.



Cross-connect Unit: change VC-4,VC-3,VC-12 level signal’s direction & channel.



Timing Unit: provide timing signal for the system.



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Auxiliary Unit: provide kinds of Auxiliary interfaces to monitor the equipment & signals’ status.

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Totally six main units:

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

SCC Unit: collect alarm and performance events & communicate with another HUAWEI’S SDH equipment in the same network.

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P-6

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P-7

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

The OptiX OSN series sub-rack can be installed in a 300-mm or 600-mm deep ETSI cabinet.



The external case-shaped devices can be installed in the cabinet as required.  



COA

s e c r u o s e R

Fiber management spool, which is used to spool the redundant fibers inside the cabinet.

For 600MM depth cabinet two sub-racks can not be installed as back to back. It is just to say the same height cabinet installed the same kind equipment’s sub-rack number are the same.

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P-8

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The indicators on the ETSI cabinet are power supply indicators and alarm severity indicators.

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

If alarm occurs, indicators will be on, not flashing.



If alarm indicator is on, alarm occurs on one or more sub-racks inside the cabinet.



The cabinet indicators are driven by the sub-rack. The cabinet indicators can be lit only after the cables are correctly connected and the sub-rack is powered on.

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P-9

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

The PDU, TN81PDU, is installed at the top of the cabinet, and is divided into two parts, namely, part A and part B that back up each other.



The TN81PDU provides eight power output interfaces, supplying power to the subracks inside the cabinet.



s e c r u o s e R

Power output area: On both sides of the DC PDU, there are respectively four output terminal blocks that are used to connect to the power cables of subracks.



Power input area: The TN81PDU supports corresponding power input capability based on the power supply capacity of the telecommunications room.

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When the telecommunications room provides four power inputs not less than 32 A, part A and part B can respectively be connected to four -48 V DC power cables and four power ground cables, that is, eight -48 V DC power cables and eight power ground cables in total  When the telecommunications room provides two power inputs not less than 63 A, part A and part B can respectively be connected to two -48 V DC power cables and two power ground cables, that is, four-48 V DC power cables and four power ground cables in total Power switch area: On both sides of the DC PDU, there are respectively four power output switches that correspond to the output terminal blocks. The power output switches control power supply to the corresponding subracks. 

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P-10

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On the top of the ETSI cabinet, there are cabinet indicators and a DC power distribution unit (PDU). The OptiX OSN series supports the input of –48 V or –60 V DC power supply.



The Voltage range of input power supply should be –38.4 V to –57.6 V or –48 V to –72 V.

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P-11

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The sub-rack of the OptiX OSN 3500 adopts a two-tier structure. The structure is divided into board area, fan area, and fiber routing area.



Interface board area: for various OptiX OSN 3500 interface boards.



Fan area: for three fan modules, enabling heat dissipation function.



Processing board area: for all processing boards of the OptiX OSN 3500.



Fiber routing area: for fiber routing.

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P-12

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The sub-rack of the OptiX OSN 3500 has two tiers. The upper tier gives 16 slots for interface boards. The lower tier gives 18 slots, 15 slots of them for processing boards.



Slots for Interface Boards: slots 19–26, slots 29–36.



Slots for Processing Boards: slots 1–8 and slots 11–17.



Slots for Other Boards.

or



XCS boards: slots 9–10



GSCC boards: slots 17–18 (Slot 17 can also hold a service processing board)



Power interface boards: slots 27–28



Auxiliary interface boards: slot 37

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Dual slot can pass though the DCC byte and orderwire byte by hardware if the SCC board is offline.

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The OptiX OSN 3500 offers a 200 Gbit/s, 80 Gbit/s or 40 Gbit/s cross-connect capacity according to the type of cross-connect boards. 

s e c r u o s e R

622M x 8+2.5G x 4+10G x 2=35G

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P-14

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1.25G x 7+2.5G x 4+10G x 4=58.75G

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P-15

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5G x 7+10 G x 4+ 20 G x 4=155G

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P-16

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P-17

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P-18

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

We can not use the processing board solely. Because on processing board there are no interface to access the signal, so we should use the corresponding interface board together to provide specific interface to access the signal.



CAUTIONS: 



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

Wear the anti-static wrist strap when holding the board with hands. Make sure that the anti-static wrist strap is well grounded. Otherwise, the static discharge may cause damage to the board.

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Do not directly insert the attenuators into the level optical modules. If the attenuators are required, use the attenuators at the ODF side. If a board requires an attenuator, insert the attenuator in the IN interface instead of the OUT interface. When performing the loopback, use attenuators to prevent damage to the optical modules.

Laser Safety Class  



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The safety class of the laser on the board is CLASS 1. The maximum launched optical power of the optical interfaces is lower than 10 dBm (10 mW).

DANGER 

Avoid direct eye exposure to laser beams launched from the optical interface board or optical interfaces. Otherwise, damage may be caused to the eyes.


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P-19

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P-20

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

LC: Lucent connector.



A: support SFP module



F: support FEC (Forward Error Correction) function



I-64.2: I: Internal



L: Long distance



S: Short distance



64: STM-64 16:STM-16



1: Wavelength is 1310nm, used for G.652 fiber



2: Wavelength is 1550nm used for G.652 fiber



3: Wavelength is 1550nm used for G.653 fiber

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

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P-21

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SL64/SF64 cannot support SFP module



SFP: Small Form-Factor Pluggable

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P-22

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SLH1 is a 16 x STM-1 electrical signal processing board.



SEP1 is a 2 x STM-1 electrical signal processing board, with two STM-1 electrical interfaces on the front panel.



SEP1 is an 8 x STM-1 electrical signal processing board with interface board, in this case, the SEP1 we should create it on NMS as SEP.



EU08, EU04 and OU08 are interface boards of the SEP&SLH1. The TSB8 and TSB4 are electrical interface switching and bridging boards.



When used with different interface boards and electrical interface switching and bridging boards, the SEP1 and SLH1 have different access ability.

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P-23

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The optical interface of the N1OU08 uses the LC connector. The optical interface of the N2OU08 uses the SC connector. The N1OU08 uses the pluggable optical module. The N2OU08 does not use the pluggable optical module.

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P-24

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

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The O/E conversion module includes E/O (O/E) conversion and MUX/DEMUX part. The O/E conversion converts the received 2.666 Gbit/s FEC optical signals into electrical signals and detects R_LOS alarms.

s e c r u o s e R

The DEMUX part demultiplexes the high rate electrical signals into multiple parallel electrical signals, and recovery the clock signal at the same time. The multiple electrical signals demultiplexed are transferred to the digital packet encapsulation and FEC processing module to have FEC packets decapsulated and SDH overheads processed.

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The SDH overhead processing module extracts overhead byte from the received multiple electrical signals, performs pointer processing, and then sends the signals to the crossconnect unit through backplane bus. R_LOF, R_OOF, AU_LOP and AU_AIS alarms are detected in this module.

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

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Receiving direction:

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Transmitting direction 





After being inserted with overhead bytes in the SDH overhead processing module, the parallel electrical signals from the cross-connect unit are then sent to the digital packet encapsulation and FEC processing module. The digital packet encapsulation and FEC processing module performs FEC coding and SDH overhead inserting to the multiple signals, and then sends it to the O/E conversion module. The O/E conversion module multiplexes the received parallel electrical signals into high rate electrical signals through the MUX part, converts the signals into SDH optical signals. Signals are then sent to fibres for transmission.


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P-25

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

Different boards have different appearance and dimensions.



The barcode on the front panel of the board indicates the board version, name and board features.



Two types of barcodes are used for the boards of the OSN series. 

16-character manufacturing code + board version + board name + board feature code





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20-character manufacturing code + board version + board name + board feature code

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For details on the board feature code, please refer to the section that describes the board feature code for each board on equipment hardware manuals.

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P-26

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P-27

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P-28

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P-29

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

PDH service processing boards include the boards which can process E1/T1, E3/DS3, E4/STM-1 services.



Naming rules of PDH service processing boards: 

S - SDH



P - PDH



M - MIX

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

PL3A has three pairs of 75-ohm unbalanced SMB interfaces, and can work without interface board; PL3 must work with C34S.



D75S - 75 means the interface impedance is 75Ω; D12S – 12 means 120 Ω.

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The difference between D12S and D12B is: D12S supports TPS configuration, while D12B does not.

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P-30

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Indicators of SPQ4： 

STAT: Board hardware status indicator



ACT: Board activation status indicator



PROG: Board software status indicator



SRV: Service status indicator

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

MU04 is the interface board for SPQ4 with SMB connector, for E4/STM-1 signal.



There is no indicator on MU04.

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P-31

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Functions of PQ1: 

Receiving Direction 

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The E1 signal enters through the interface module, the decoder where HDB3 or B8ZS data signal and clock signal are recovered. Then, the signal is sent to the mapping module.



In the mapping module, the E1 signal is mapped asynchronously to C-12, and formed as VC-12 after channel overhead processing, as TU-12 after pointer processing, and finally as VC-4 through multiplexing. Then, the signal is sent to the cross-connect unit.

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

Transmitting Direction 

The de-mapping module extracts binary data and clock signals from the VC-4 signal from the cross-connect unit, and sends the signal to the encoder, where E1 signals are output.


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P-32

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

There are two types of PQ1: PQ1A (75Ω) and PQ1B (100Ω/120Ω).



Warm reset will not affect the running service, while cold reset may affect the service.



TPS: Tributary Protection Switching. It is intended to protect several (N) tributary

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processing boards through a standby tributary processing board . 

PRBS: Pseudo-Random Binary Sequence. The PRBS function is mainly used for network selftest and maintenance. An NE that provides the PRBS function can work as a simple device used to analyze if a service path is faulty. Such analysis can be performed for the NE and the entire network. During deployment or troubleshooting, the PRBS function realizes the test without a real test device.

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P-33

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If there is no interface port on the board, then the board must work with an interface board.

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P-34

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P-35

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P-36

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





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Collect alarm and performance events.



GFP: Generic Framing Procedure.

Receiving Direction

The interface module accesses 100BASE-SX/LX/ZX signals from external Ethernet equipment (such as LAN switch and router) and performs decoding and serial or parallel conversion to the signals. Then it sends signals to the service processing module for frame delimitation, preamble field code stripping, cyclic redundancy code (CRC) termination and Ethernet performance statistics. At the encapsulation module, HDLC, LAPS or GFP-F encapsulation is done to the Ethernet frame. After that, the services are mapped into VC-3 or VC-4 at the mapping module and then sent to the cross-connect unit.

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Convert Ethernet signal to VC-4 or VC-4 concatenated signal and convert VC-4 or VC-4 concatenate signal back to standard Ethernet signal.



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Function of EFS4

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Transmitting Direction 

De-map the VC-3 or VC-4 signals from the cross-connect unit and send them to the encapsulation module for decapsulation. The service processing module determines the route according to the level of the equipment; it also provides frame delimitation, adding preamble field code, CRC calculation and performance statistics. Finally, the interface module performs parallel or serial conversion and encoding to the signals and then sends them out from the Ethernet interface.


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P-37

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

LCAS: Link Capacity Adjustment Scheme.



Testing frame only for GFP protocol.



EPL: Ethernet Private Line.



EPLAN: Ethernet Private Local Area Network.



EVPL: Ethernet Virtual Private Line.



EVPLAN: Ethernet Virtual Private Local Area Network.

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P-38

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XCE can be used in extended sub-rack only.

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P-39

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Note: When OptiX OSN 3500 is configured as an extended sub-rack, the EXT port of AUX board should be connected to the one of main sub-rack.

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P-40

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Standard SSM mode: A mechanism for synchronization management in SDH network, is loaded in the lower four bits of S1 byte in SDH overhead. It allows the exchange of the quality information of clock source among nodes. Thus, the Timing Unit can automatically

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choose the clock source of the highest quality and priority to prevent clock mutual tracing. 

Extended SSM mode: Huawei raises the concept of clock source ID, which is defined using the higher four bits of S1 byte and is transmitted with SSM together. When a node receives the S1 byte, it checks the clock source ID to determine if it is originated from this station. If so, the clock source is unavailable, thus the clock loop can be avoided when the clock tracing trail is configured as a ring.



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Stop SSM mode: The Timing Unit selects and switches the clock source based on the priority table. The available clock source with highest priority is selected as the tracing

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P-41

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P-42

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Control Module

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The control module configures and manages boards and NEs, collect alarms and performance events, and backs up important data.

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Communication Module 

The communication module provides 10 Mbit/s and 100 Mbit/s compatible Ethernet interface for the connection between the NE and the T2000, F&f interface for managing external devices such as COA, and the OAM interface.

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Overhead Processing Module The overhead processing module receives overhead signals from the line slot and processes such bytes as E1, E2, F1 and serials 1-4. The overhead processing module also sends overhead signals to the line board, and externally provides one orderwire interface, two SDH NNI audio interfaces, interface F1, and the broadcast data interfaces serials 1-4.


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P-43

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The power monitoring module comprises –48 V power monitoring and working power.

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The working power provides the GSCC with working voltage and detects and switches the active and standby 3.3 V power supply (which is provided through AUX).

The –48 V power monitoring module monitors the +3.3 V power alarm of AUX, monitors fan alarms, monitors and manages the PIU, and processes sixteen housekeeping alarm inputs and four housekeeping alarm outputs as well as the cabinet alarm indicator signal, monitors the over-voltage of -48v and produces corresponding power alarm.

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Power Monitoring Module

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P-44

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P-45

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If there are two subnets which are not connected by fibers, ethernet cables can be applied to establish the extended ECC communication. In this way, the U2000 can manage these equipment in a centralized manner. One NE will work as a server and anther one is a client.

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P-46

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The mdb is in the dynamic random-access memory (RAM), saving the current databases. The drdb is saved in flash RAM and D RAM. When power failure occurs to NE, the databases will be recovered in the order of drdb® fdb0® fdb1. The drdb will be checked

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first for configuration data. If the configuration data are safe in drdb, they will be recovered to mdb from drdb; if they are damaged, data will be recovered from fdb0 or fdb1, depending on which saves the latest data. If data in fdb0 are also damaged, fdb1 is used for data recovery. Therefore, it is important to back up data to fdb0 and fdb1 and compare the data in them.

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P-47

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

The AUX, EOW, SAP and SEI are the system auxiliary interface board, providing the system with various auxiliary interfaces, management interfaces, central backup of the +3.3 V board power supply, orderwire interface and broadcast data interface.



The BA2 is a 2-port booster amplifier board. The BPA is a booster amplifier & pre-amplifier board.



The COA, a case-shape optical amplifier, integrates the EDFA module, drive circuit and communication circuit in an aluminium case. Three types of COA are available: 61COA, N1COA and 62COA.



The DCU is the dispersion compensation board. It can compensate for the optical signal dispersion accumulated during transmission in the 10 Gbit/s system. In addition, it compresses the optical signal and works with the booster amplifier to achieve long distance optical transmission.

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The PIU is a power interface board. It functions power access, lightening protection and filtering.



The uninterruptible power module (UPM), numbered GIE4805S, is a special power supply system. It can convert 110 V/220 V AC power supply directly to –48 V DC needed by transmission equipment, such as OptiX OSN 2500. It is suitable for telecom carriers who do not have –48 V DC power supply equipment or who require storage batteries.



The OptiX OSN equipment uses the modularized fan. The FAN is a fan control board, responsible for fan speed adjustment, fan failure detection and failure report, as well as report of the fan not-in-position alarm.


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P-48

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



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Provide the U2000 interface for active/standby SCCs, OAM interface for remote maintenance, and interfaces for inter-board communication.

Interface Module

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

Provide various auxiliary interfaces, such as F&f, OAM, F1 and clock input/output.



The N1 AUX and R1/R2 AUX provide different auxiliary interfaces.

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The AUX consists of communication module, interface module and power module.

Communication Module 

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Principle Of AUX

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

Provide the AUX with working power, and other boards on the subrack with +3.3 V centralised backup power.

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P-49

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P-50

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

The DCU is used to compensate the accumulated dispersion during the transmission of the 10 Gbit/s system, suppress optical pulse signals, recover optical signals, and realize the long-haul transmission with optical regeneration when used with optical amplifier board.



During the long-haul transmission (more than 80 km) of 10 Gbit/s signals, the pulse width of optical signals is expanded and signals are distorted because of dispersion. As a result,

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the optical signals cannot be normally received by the optical receiver. Thus, the DCU should be used to compensate the dispersion.

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P-51

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P-52

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P-53

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P-54

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P-55

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P-56

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P-57

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P-58

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P-59

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

TPS of E1/T1 service does not need TSB4/TSB8 board.



1:8 TPS of E1/T1 board: slot1 is for protection board，while slot2 - slot5 and slot13 slot16 are for working boards.

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P-60

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P-61

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P-62

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OptiX SDH Networking and Self-Healing Protection

P-1

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Content

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

SDH Network Topologies...............................................……………….....................Page 2



Survivable networks and their protection mechanisms…………………….…………Page 14

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P-2

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Through this course, trainees should be able to: 

List the SDH different topologies structures, features and applications.



Have idea about the basic concept of the SDH network protection. And understand

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the network objectives, application architecture, switching initialization and restoration criteria, characteristics, network capacity of different types of network protection. 

References 

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ITU-T Recommendation G.841 (Oct, 1998) Types and characteristics of SDH network protection architectures





ITU-T Recommendation G.810 (Aug, 1996) Definitions and terminology for synchronization networks ITU-T Recommendation G.803 ITU-T Recommendation G.803 (Aug, 2003) Architecture of transport networks based on the synchronous digital hierarchy (SDH)


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P-4

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P-5

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The network topology, the geometrical layout of SDH network nodes and transmission lines, reflects the physical connection of the network. The network topology is important in the sense that it determines the performance, reliability and cost-effectiveness of an SDH network.

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P-6

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P-7

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The chain network is simple and economical at the initial application stage of SDH equipment. For a chain network, it’s more difficult and more expensive to protect the traffic, compared with a ring network. The chain network is used in cases where the traffic

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is unimportant or where the traffic load is small so that we don’t have to care about the traffic protection.

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P-8

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In the star network, the hub node selects routes and passes through the traffic signals for all the other nodes. As a result, the hub node is able to manage the bandwidth resources thoroughly and flexibly. On the other hand, there is the possibility of a potential bottleneck

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of bandwidth resources. Besides, the equipment failure of the hub node may result in the breakdown of the entire network.

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P-9

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A tree structure can be considered as the combination of chain and star structures. It is suitable for broadcast service. However, due to the bottleneck problem and the optical power budget limit, it is not suitable for bidirectional traffic.

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P-10

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

The ring network is the most widely used network for SDH transmission networks.



In such a structure, any traffic between two adjacent nodes can be directly add/drop between them. For traffic between two non-adjacent nodes, we have to configure the

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add/drop traffic at the source node and the sink node. And the pass-through traffic in between those two nodes must be created as well. 

The ring network is highly survivable. The most obvious advantage of a ring network is its high survivability that is essential to modern optical networks with large capacity. Thus, the ring network enjoys very broad applications in SDH networks.

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P-11

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Mesh networks are such communications networks in which many nodes are interconnected with each other via direct routes. In such topological structure, if direct routes are used in the interconnection of all the nodes, this structure is considered as an

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ideal mesh topology. In a non-ideal mesh topological structure, the service connection between nodes that are not connected directly is established through route selection and transiting via other nodes. 

In a mesh network, no bottle neck problem exists. Since more than one route can be selected between any nodes, when any equipment fails, services can still be transmitted smoothly through other routes. Thus, the reliability of service transmission is increased. However, such networks are more complicated, costly and difficult to manage. Mesh networks are very suitable for those regions with large traffic.

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P-12

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

Tangent ring networks / Intersectant ring networks/ Not protection chain.



In selecting a topological structure, many factors should be considered. For example, the network should be highly survivable, easy to configure, suitable to add new services, and

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simple to mange. In a practical communications network, different layers adopt different topological structures.

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P-13

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The advantage of sub-network can simplify the big network, make it easy to maintenance.

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P-14

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

The concept of sub-network is introduced in Huawei OptiX series equipment and network management systems in order to facilitate network topology management, security management, tributary interface expansion, and traffic management.



In practical applications, it simplifies the topology structure of complicated networks and thus enables hierarchical management.

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P-15

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P-16

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P-17

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Modern society is getting more and more dependent on communications with the development of science and technologies, and so higher requirements to network security are being brought forward. Thus the concept of survivable network comes into being. The

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following will deal with the concepts of survivable network.

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P-18

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

Please pay attention to that the network can only restore services here. It cannot repair the failure in the network, which cannot do without human intervention.



So there should have protection channels to carry over the services in the working

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channels. The first requirement for survivability of network is there should have protection routes or standby routes. 



A survivability also need something else. Nodes in the network must have the intelligence to check out the failure occurred and inform corresponding units of doing relative protection operation. And the nodes also should have powerful cross-connect capability to implement the protection operation.

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For the survivable network, the protection object can be the physical or electronic.

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P-19

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P-20

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Unidirectional traffic and bidirectional traffic are named regarding the traffic flow directions in the ring. A unidirectional ring means that traffic travel in just one direction, e.g. clockwise or counter-clockwise. While in a bidirectional ring, traffic signals go in two

s e c r u o s e R

directions, one opposite to another. 

t t :h

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Protection modes can be divided into two kinds: 1+1 and 1:N. In 1+1 protection mode, every working system is protected by a dedicated protection system. But in 1:N protection mode, N systems share one protection system; and when the system is in normal operation, the protection system can also transmit extra traffic. Thus a higher efficiency can be obtained than that of 1+1 system.



g n ni

r a e

For multiplex section protection ring, traffic protection is based on multiplex section. Switching or not is determined by signal qualities of the multiplex section between each

L e

or

span of nodes.

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P-21

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

The network has two channels (two pairs of fibers): working (active) channel and protection (standby) channel.



When the network is normal (i.e. no failure on working channel), working channel is used

s e c r u o s e R

to transport the traffics. 

When the working channel is failed, use the protection channel.



Linear Multiplex Section (MS) protection is one of multiplex section protections. Linear multiplex section protection switching can be a dedicated or shared protection mechanism. It protects the multiplex section layer, and applies to point-to-point physical networks. One protection multiplex section can be used to protect the normal traffic from a number (N) of working multiplex sections. It cannot protect against node failures. It can operate in a unidirectional or bidirectional manner, and it can carry extra traffic on the protection

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multiplex section in bidirectional operation.

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P-22

/e m o i.c

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

Source node: concurrent sending



Sink node: selective receiving

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P-23

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Out of 1+1 linear multiplex section protections, some modes require APS protocol during the switching process, some don’t require. For 1  1 unidirectional switching, the signal selection is based on the local conditions and requests. Therefore each end operates

s e c r u o s e R

independently of the other end, and bytes K1 and K2 are not needed to coordinate switch action.

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P-24

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

When the network has no failure, N working channels can transmit the normal traffic while the protection channel transmits extra (unimportant) traffic or it transmits no traffic.



Suppose the fiber from NE A to NE B of the working channel 1 is broken. NE B detects

s e c r u o s e R

R_LOS alarm and sends a request to NE A to switch the services on the failed channel to the protection channel. 

Upon receiving the request, NE A bridges the service on the failed channel to the protection channel.



NE B get the information from NE A and switch to select the service from the protection channel.



NE A switches to select the service from the protection channel. This step completes the switching of the service on the faulty channel to the protection channel for both directions.

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P-25

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// : p

When the working channel 1 repaired, the _RLOS alarm disappears. NE B sets the K1 byte to “Wait-To-Restore (WTR)” state. If WTR state lasts for a special time (10 minutes by default), it switches to select the signal from the working channel and sends “No Request”

s e c r u o s e R

signal to the NE A using K1 byte. 

t t :h

r a le

g n ni

NE A releases the bridge and replies with the same indication on K1 byte. The selector at the NE A is also released.



Receiving this K1 byte causes the NE B to release the bridge. This step completes the protection recovery.

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P-26

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

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In 1+1 protection mode, every working system is protected by a dedicated protection system. But in 1:N protection mode, N systems share one protection system; and when the system is in normal operation, the protection system can also transmit extra traffic. Thus a

s e c r u o s e R

higher efficiency can be obtained than that of 1+1 system, but a more complicated APS protocol is needed. This protection mode mainly protects the normal traffic in case optical cable of the working multiplex section is cut off or multiplex section performance degrades.

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P-27

/e m o i.c

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

t t :h

Answer 

Linear 1+1 MS



Linear M:N (M=1)

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P-28

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

In OSN networking application, there is no PP ring. But when we need to create a protection sub-net when using the NMS T2000.



The protection switching principle of two-fiber bidirectional path protection ring is

s e c r u o s e R

basically the same as that of unidirectional path protection ring, except that in two-fiber bidirectional path protection ring, the route of receiving signals is consistent with that of sending signals 

Two-fiber unidirectional MS dedicated protection ring is composed of two fibers. Working channels and protection channels are carried over different optical fibers. Of course, fiber P1 can be used to carry extra traffic when not used for protection. The two-fiber unidirectional Multiplex Section dedicated protection ring is seldom used in actual applications since it has no advantages over either the two-fiber unidirectional path

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protection ring or two-fiber bidirectional multiplex section shared protection.

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P-29

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

The orderwires can be passed through used the backboard in the dual slots



When we are facing the sub-rack, the left hand side is the West line board, the right hand side is the East line board



The W was used for the source node



The E was used for the sink node

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P-30

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On each fiber, half the channels are defined as working channels and half are defined as protection channels. The normal traffic carried on working channels in one fiber are protected by the protection channels in another fiber traveling in the opposite direction

s e c r u o s e R

around the ring. This permits the bidirectional transport of normal traffic. Only one set of overhead channels is used on each fiber.

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P-31

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For example, a STM-16 system shall assign #1--- #8VC4 as the working channels, #9---#16 as the protection channels. One fiber of #9---#16 are to protect #1---#8 of another fiber.

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P-32

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For two-fiber bidirectional multiplex section protection rings, as their traffic have uniform routes and are sent bidirectional, time slots in the ring can be shared by all nodes, so the total capacity is closely related to the traffic distribution mode and quantity of nodes on the ring.

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P-33

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

When a node determines that a switch is required, it sources the appropriate bridge request in the K-bytes in both directions, i.e. the short path and long path.



The destination node is the node that is adjacent to the source node across the failed span.

s e c r u o s e R

When a node that is not the destination nodes receives a higher priority bridge request, it enters the appropriate pass-through state. In this way, the switching nodes can maintain direct K-byte communication on the long path. Note that in the case of a bidirectional failure such as a cable cut, the destination node would have detected the failure itself and sourced a bridge request in the opposite direction around the ring. 

g n ni

When the destination node receives the bridge request, it performs the bridge and bridges the channels that were entering the failed span onto the protection channels in the opposite direction. In addition, for signal fail-ring switches, the node also performs the

r a e

L e

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switch to protection channels.

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P-34

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t t :h

WTR: wait to restore

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P-35

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APS requests are also initiated based on multiplex section and equipment performance criteria detected by the NE. All the working and protection channels are monitored regardless of the failure or degradation conditions (i.e. after a switch has been completed,

s e c r u o s e R

all appropriate performance monitoring is continued). The NE initiates the following bridge requests automatically: Signal Failure (SF), Signal Degrade (SD), Reverse Request (RR), and Wait to Restore (WTR). The bridge requests are transmitted from NE to NE (not from NMS to NE).

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P-36

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The APS controller is responsible for generating and terminating the APS information carried in the K1K2 bytes and implementing the APS algorithm. With the switching state of each NE, the APS controller status is also changed.

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P-37

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

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For two-fiber bidirectional multiplex section protection rings, as their traffic have uniform routes and are sent bidirectional, time slots in the ring can be shared by all nodes, so the total capacity is closely related to the traffic distribution mode and quantity of nodes on

s e c r u o s e R

the ring. The network capacity for two-fiber bidirectional multiplex section ring is ½ *M*STM-N (M is the number of nodes on the ring, STM-N is the STM level). If we count the protection channels as well, the maximum traffic load that a two-fiber bidirectional MS shared protection ring can carry is M*STM-N. Nevertheless, half of the traffic would not be protected in case of fiber failures.

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P-38

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Four-fiber MS shared protection rings require four fibers for each span of the ring. Working and protection channels are carried over different fibers: two multiplex sections transmitting in opposite directions carry the working channels while two multiplex sections,

s e c r u o s e R

also transmitting in opposite directions, carry the protection channels. This permits the bidirectional transport of normal traffic. The multiplex section overhead is dedicated to either working or protection channels since working and protection channels are not transported over the same fibers.

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P-39

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In the normal situation, the services will be transmitted on the working fibers

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P-40

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

When the fibers between two nodes broken, the switching will happen between these two nodes



In the other sections, the services will be transmit on the original routes

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P-41

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

When all the fibers between two NEs broken, the ring switch happens



All the services will go to the protection fibers

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P-42

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APS requests are also initiated based on multiplex section and equipment performance criteria detected by the NE. All the working and protection channels are monitored regardless of the failure or degradation conditions (i.e. after a switch has been completed,

s e c r u o s e R

all appropriate performance monitoring is continued). The NE initiates the following bridge requests automatically: Signal Failure (SF), Signal Degrade (SD), Reverse Request (RR), and Wait to Restore (WTR). The bridge requests are transmitted from NE to NE (not from NMS to NE).

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P-43

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P-44

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For four-fiber bidirectional multiplex section protection rings, as their traffic have uniform routes and are sent bidirectional, time slots in the ring can be shared by all nodes, so the total capacity is closely related to the traffic distribution mode and quantity of nodes on

s e c r u o s e R

the ring. The network capacity for four-fiber bidirectional multiplex section ring is M*STMN (M is the number of nodes on the ring; STM-N is the STM level). If we count the protection channels as well, the maximum traffic load that a four-fiber bidirectional MS shared protection ring can carry is 2*M*STM-N. Nevertheless, half of the traffic would not be protected in case of fiber failures.

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P-45

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K1 bits 1-4 carry bridge request codes. K1 bits 5-8 carry the destination node ID for the bridge request code indicated in K1 bits 1-4.

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P-46

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

As network structures are becoming more and more complicated, the sub-network connection protection (SNCP) is the only traffic protection mode that can be adapted to various network topological structures with a fast switching time.



The protection mechanism of SNCP is similar to the PP ring. But for SNCP, the protection function will be completed in the cross-connect unit not PDH unit.

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P-47

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As shown in the figure , SNCP uses the 1+1 protection mode. Traffics are simultaneously sent on both the working and protection sub-network connection. When the working subnetwork connection fails, or when its performance deteriorates to a certain level, at the

s e c r u o s e R

receiving end of the sub-network connection, the signal from the protection sub-network connection is selected according to the preference selection rule. Switching usually takes the unidirectional switching mode, thus it needs no APS protocol.

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P-48

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P-49

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

The protection mechanism of SNCP ring is concurrent sending in the transmitting end and selective receiving in the receiving end.



Here is a ring chain combination network with 5 nodes. The ring network is SNCP ring.



Suppose that there have E1 services from node A to the end node of the chain. The services will concurrently sent to both working SNC and protection SNC. After passing

s e c r u o s e R

through subnetwork1 and subnetwork2 separately, they both reach node C. there is a selector in node C, the SNC termination node. Normally, node C will receive the service from the working SNC, then pass through to the line unit in the chain.

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P-50

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

TU-LOM (HP-LOM): tributary unit – loss of multi-frame, a consecutive of 2-10 frames of H4 are not in the order of the multi-frame or have invalid H4 values.



TU-LOP: tributary unit loss of pointer, a consecutive of 8 frames receives invalid pointers or NDF.



s e c r u o s e R

HP-TIM: higher order path trace identifier mismatch, what J1 should receive is not consistent with it actually receives, generating this alarm in this terminal.



HP-SLM: higher order path signal label mismatch, what C2 should receive is not consistent with it actually receives, generating this alarm in this terminal.

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

If the signal failure recovers in any way, node C would switch back to receive services from working SNC after 10 minutes.



10 minutes is the default restoration time. It can be set from 5 to 12 minutes.

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P-55

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P-1

iManager NMS system introduction

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

1. Architecture and Main Features of U2000 …………………..……………………….… 3



2. Directory Structure of U2000……………………………………………………….….…19



2.Main Functions of U2000 ……..…………………………………………………….….…22

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Upon completion of this chapter, you will be able to: 

List 8 pieces of main functions of U2000.



Describe the realization means of U2000



Perform some basic operations of U2000.

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This is the position figure of the U2000 in telecommunication management network (TMN). There are 5 layers of TMN as follows:

s e c r u o s e R



Network element layer, whose management software is local craft terminal (LCT)



Element management layer, which manages and configures individual NE as a whole.



Network management layer, which is used to manage a large scale or distributed network.



Service management layer, which supports integrated service operation management including service lease, bandwidth wholesale, VPN etc.



Business management layer, which provides the customer relationship capabilities that include billing, customer care, and service-level agreements. This layer is also primarily where internal business management applications share information with external applications.

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Traditional Operations Support Systems (OSS) contain three layers of management: (i) a Business Management Layer, (ii) a Service Management Layer, and (iii) a Network Management Layer. OSS is a part of business and operation support systems (BOSS).


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

The U2000 provides a unified platform for managing transport equipment, Access equipment, and datacom equipment (routers, switches, and security equipment), thus realizing integrated management on cross-domain equipment. In addition, the U2000 breaks the restrictions of the vertical management mode and realizes integrated management on the equipment at the network layer and NE layer.



The U2000 meets the network integration trend and can provide management schemes for multiple types of networking scenarios. With unified and consistent GUIs, simple and convenient service deployment, and effective service monitoring and assurance, the U2000 brings good user experience and greatly reduces network operation and maintenance costs.

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The features of the U2000 are as follows:

r a le

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

The U2000 is blessed by the good cooperation relationships between Huawei and many mainstream OSS vendors. The U2000 can provide abundant NBIs and

powerful NBI customization support, protecting user investment to the largest extent.


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The Characteristic of New Architecture：

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

Core modules split from single Process to multi Process.



E2E modules split mutil Process by service.



NEs manager modules split independent NE manager.



System stronger than before, single Process failed doesn’t affect other Process.

s e c r u o s e R

The advantages of the architecture: NE manager, E2E service management adopted independent Process, which can support system distributed deployment and expended management capability smoothly.

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

The client of U2000 implement the workstation function (WSF) of TMN, by which the user can operate and manage any transaction on the network.



The server of U2000 implement the operating system function (OSF) of TMN, save the network data, provide performs all kinds of management function on the network.



The client and server of U2000 can be installed on PC or workstation. But it is recommended to run the client on the Windows platform. The operating system and database versions should be as follows: 

or



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UNIX operating system version on SUN workstation is Solaris 10 and the database version is Sybase 15.0;

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M

r a le

g n ni



PC operating system supports Windows Server 2003, while the database is Microsoft SQL Server 2000 Standard.



Linux operating system version is SUSE Linux 10 SP2 while the database is SYBASE 12.5.

Key features of U2000 architecture: 

Excellent system structure;



Standard interfaces and high integration;



High efficiency and robustness.


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P-9


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

TMN defines northbound interface (NBI) to be used in connecting upper level system while southbound interface (SBI) connecting lower level system or equipment.



Corba (Common Object Request Broker Architecture) interface is one of the standard

s e c r u o s e R

interfaces, by which U2000 can communicate with the NMS developed by other vendors 

SNMP (Simple Network Management Protocol) interface is one of the standard interfaces used in the industry.



The U2000 communicates with transmission GNE by Qx/TL1 interface of TCP/IP protocol,

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or OSI protocol interface. 

r a e

U2000 supports syslog protocol and radius authentication.

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P-10


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Datacom ME MA5200E/F/G, ME60 SIG SIG9810/9820 SIG9800-server Router NE40, NE80, NE40E, NE80E, NE5000E, NE05, NE08，NE08E, NE16E, NE20, NE20E AR18, AR19, AR28, AR29, AR46, AR49 Switch S8505, S8505E, S8508, S8512,S8016,S6502, S6503, S6506R, S6506, S5000, S5500, S5600, S3000, S3500, S3900 S2000，S2400,S2300, S3300, S5300, S9300,S7800E PTN PTN 910, PTN 912, PTN 950 PTN 1900, PTN 3900 Security Eudemon300, Eudemon500, Eudemon1000/E, Eudemon8040, Eudemon8080/E, Eudemon8160E,Eudemon200E_C, Eudemon200E_F CX CX200, CX200C/D, CX300 CX380, CX600

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Transmission

Access

SDH OptiX 155C, OptiX 155S, OptiX 1556/622, OptiX 2500, OptiX 2500 REG OSN OptiX OSN 500, OptiX OSN 1500, OptiX OSN 2000, OptiX OSN 2500, OptiX OSN 2500 REG, OptiX OSN 3500, OptiX OSN 7500,OptiX OSN 9500 MSTP OptiX Metro 100, OptiX Metro 200, OptiX Metro 500, OptiX 155/622H(Metro 1000), OptiX Metro 1000V3, OptiX Metro 1050, OptiX Metro 1100, OptiX 155/622(Metro 2050), OptiX 2500+(Metro 3000), OptiX Metro 3100, OptiX 10G(Metro 5000) NG WDM OptiX OSN 1800 OptiX OSN 3800, OptiX OSN 6800,OptiX OSN 8800 Metro WDM OptiX Metro 6020, OptiX Metro 6040, OptiX Metro 6100, OptiX OSN 900 LH WDM OptiX BWS OAS, OptiX BWS OCS, OptiX BWS OIS, OptiX BWS 320GV3, OptiX BWS 1600G, OptiX BWS 1600G OLA, OptiX OTU40000 Submarine OptiX BWS 1600S RTN OptiX RTN 605, OptiX RTN 610, OptiX RTN 620, OptiX RTN 910, OptiX RTN 950

BSL ISN8850/ESR8825 MA5100V1 MA5606T MA5620E MA5620G MA5626E MA5626G MA5651 MA5651G MA5680T MD5500 Radium8750 UA5000 MA5105 MA5200E/F MA5200G MA5300V1 MA5600 MA5600T MA5605

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The U2000 evaluates the management capability of different hardware platforms according to the maximum number of managed equivalent NEs and the concurrently accessed clients.

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Currently, a set of U2000 can manage up to 15,000 physical NEs, 20,000 equivalent NEs, and 100 clients. This result is provided after tests are performed under a certain environment and can be used to show the actual management capability of the U2000.

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Number of IP equivalent NEs = Number of IP NEs of type 1 x Equivalent coefficient + ...... + Number of IP NEs of type n x Equivalent coefficient

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NOTE: For example, in the case of 5 NE5000E NEs (equivalent coefficient 10), 200 S5300 NEs (equivalent coefficient 1.25), and 1,000 CX200 NEs (equivalent coefficient 0.625), the calculation

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method is as follows: Number of IP equivalent NEs = 5 x 10 + 200 x 1.25 + 1,000 x 0.625 = 925 

The basic unit of the U2000 equivalent NE is OptiX Metro 1000.

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The relation between the U2000 equivalent NE and the equivalent NE in each domain is as follows:

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1 transport equivalent NE = 1 U2000 equivalent NE

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4 IP equivalent NEs = 1 U2000 equivalent NE

The management scale of the U2000 is defined as follows: 

Small-scale management scenario: 2,000 U2000 equivalent NEs

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Medium-scale management scenario: 6,000 U2000 equivalent NEs

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Large-scale management scenario: 15,000 U2000 equivalent NEs

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Super large-scale management scenario: 20,000 U2000 equivalent NEs.


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Typical Software Requirement of HA

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OS& DB

U2000 V1R1

Remote HA Solaris

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U2000 V1R3

Veritas 5.0 MP3

Veritas 6.0

1: N HA

Remote 1:N Cold backup

Local HA

Windows Cluster

Remote HA

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Centralize the administration of multifold service and equipments.

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Function as subnetwork management system, provide powerful capability in end-to-end trail management.

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Support several open external interfaces, such as CORBA, SNMP, and XML.

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NMS operation is independent of the operation system. Windows, Solaris and SUSE Linux platforms are supported, on which the same operations are provided.

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Adopt the Client-Server structure;

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Provide Java-based graphical user interface with iLOG style in a structure of "tree on the left and table on the right“ both for Windows and Unix platform.

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In the U2000, ‘3 in 1 View Filter’ makes the Fiber layer, Trail layer, and Protection layer in one view layer. That is to say, you can check the physical topology, server and service trail and protection view simultaneously in just one window, which dispenses with the switch of working windows. Different display condition can be set in the Filter Tree depends on your factual requirement.


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The U2000 manages different function modules by using processes. After starting the U2000 server, you can view each process in the user interface of the System Monitor client.

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In the U2000, you can deploy the processes of the NE management service, network service, and NBI service independently by the Network Management System Maintenance Suite.

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In the System Monitor client, you can also get the information of database, hard disk, component, log and server status.

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MSuite: The MSuite is a graphical maintenance tool developed for the Huawei iManager U2000 (U2000), a type of Huawei network product. The MSuite is used to debug, maintain, and redeploy the U2000.

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The NMS maintenance suite focuses on functions of adding and deleting instances, and backing up and restoring the information about deployed instances and subsystems, installing and uninstalling the subsystems, NBI configuration.

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The MSuite can also backup, restore and initialize the database.

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The entrance for the NMS maintenance suite:

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Login the MSuite client. The default user and password are both admin.

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The license file is used to control the functions and resources of the U2000. If the license file is unavailable, some U2000 processes can not start and the functions of the U2000 are limited.

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The menu to check license information is Help-> License Information for U2000 V100R002.

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The menu to check license information is Help--> About --> License for U2000 V100R001.

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Precautions

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The U2000 license file naming format is: licenseXXXXXXX.dat.

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One license file corresponds to the MAC address of a network interface card in an NMS computer and can be used only on the corresponding computer.

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For a server with multiple network interface cards, you need to apply for the license of only the primary network interface card of the U2000.

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Do not make any change to the license file. Otherwise, the license becomes invalid.

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The license control items vary according to the versions of the U2000. When you fill in the application form, use the template that matches the intended version of the U2000.

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The license folder contains only one license file in the U2000\server\etc\conf\license

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directory of the U2000 V100R002. 

The license file path is U2000\server\license for U2000V100R001.


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├─client │ └─log │ └─lib │ └─patch │ └─sysmoni │ └─version ├─common │ └─tomcat │ └─SVG ├─server ├─notify ├─cau └─uninstall

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You can get the document folders as the figure shows above after the U2000 is successfully installed on your computer (Maybe a little difference): Directory

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Description U2000 Client U2000 client log U2000 client files U2000 patch and information U2000 sysmonitor files U2000 client version information Third party software Tomcat SVG view software U2000 Server Remote Notify Service CAU Uninstall

Tips: 

The installation of the folders is optional which depends on the practical requirement.

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Drawings and reports are saved in U2000\client\report by default.

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There are ‘HWENGR’ and ‘HWNMSJRE’ folders in root path or C disk after installation.


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Description U2000 Server ├─server Third Party Tools │ ├─3rdTools Execute Files, such as U2000 start/stop script │ ├─bin Configure Files │ ├─etc Configure Files of iMAP Platform │ │ ├─conf U2000 License │ │ │ ├─license Configure Files of U2000 System │ ├─conf U2000 log │ ├─log The ENV setting script of U2000 │ ├─svc_profile.sh Output data of U2000 running time │ ├─var Data backup │ │ ├─backup Running time data of broadcast │ │ ├─broadcast Database temp data │ │ ├─dbdata Running time data of fault subsystem │ │ ├─fm U2000 log for iMAP platform │useful │ ├─logs The link of U2000 (The installation path is D:\ as example.) Tools │ └─tools U2000server D:\U2000\server\bin\startnms.bat

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D:\U2000\server\bin\stopnms.bat 

U2000sysmonitor

D:\U2000\client\startup_sysmonitor_global.bat

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U2000client

D:\U2000\client\startup_all_global.bat

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Msuiteclient

C:\HWENGR\engineering\startclient.bat

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Msuiteserver

C:\HWENGR\engineering\startserver.bat C:\HWENGR\engineering\stopserver.bat


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Tips:

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Please accustom yourself to often use the right click of the mouse and F1 key on the keyboard during the operation, you can get some useful shortcuts and help.

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Right click on different objectives can lead you to the entrances of many frequently used operations.

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Using F1 key can make you get correlative help information or description in different operation windows.

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In topology management, the managed equipment and their connection status are displayed in a topological view. The managed objects are organized in submaps and views. You can browse the

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topological view to know the status of the entire network in real time. 

The U2000 provides the physical view, L2 view, RPR view, IP view, cluster view, and MPLS TE view. Therefore, users can browse the required information in different views and also monitor and learn information about the running status of the entire network.

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Function of Topological View

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An U2000 topological view consists of a navigation tree on the left and a view on the right. The

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navigation tree directly reflects the network hierarchy. The view displays the objects at different

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coordinates in the background map. 

The topological view provides you with the following functions:

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Add, delete, modify, cut, move to and paste a submap.

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Add, delete, modify, cut, copy, copy to, move to, and paste a topology node.

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Zoom in or out on topological views.

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Set a background map. You can know the position of an equipment node through its icon in the background map.

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Find topology objects globally. You can identify an object.

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Provide a navigation tree through which you can quickly switch between views.

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Provide the aerial view, print function, and filter function.

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Support the custom view. You can define and organize different views according to the actual requirements.


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NE Status

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Verify Configuration

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NE Time Synchronization

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Synchronize Current Alarms

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Browse Current Alarms

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Clear Alarm Indication

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Browse Performance

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Refresh Board Status

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Backup NE Database to SCC

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There is an blank area at the bottom of NE Panel, when you left click on a board, the corresponding information of the board is displayed.

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Right click on the board and you can get the entrances of many frequently used

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The NE Panel displays the slots, boards, and ports of the subrack in different colors. You can check the legend (click the corresponding shortcut icon at the top of the NE Panel) and get the status of the slots, board and ports. Most of the operations such as equipment configuration, monitoring, and maintenance are performed in the NE Panel.

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Tips:

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NE Explorer is the main operation interface of the U2000. For easy navigation, the NE Explorer window presents an expandable directory tree (Function Tree) in the lower left pane. The configuration, management and maintenance of the equipment are accessed here.

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NE functions include: 

Configuration

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Alarm

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Performance

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Communication

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Security

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ASON (Automatic Switched Optical Network)

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Board functions include: 

Configuration

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Alarm

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For this course, we take a window of SDH service configuration as an example, which is applied to the following scenarios:

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Create SDH service in Single Station method.

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Query and maintain the cross-connection of a single station.

Tips: The cross-connection created in End-to-End Trail method is still displayed in this interface.

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In the ‘Overhead Management’, you can query and configure the overhead bytes including J0, J1, J2, C2 and Overhead Termination.

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This operation is commonly applied to interconnecting with the equipment provided by a third party.

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You can configure the parameters of each boards including interface boards. U2000 provides the parameters configuration such as loopback, service load, laser switch etc, which are important and helpful to maintenance work.

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Tips: Generally speaking, the parameters of Ethernet board should be changed based on different services, while other cards, the PDH board and SDH board, for example, can work in the default configuration.

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This operation is mainly applied to NE communication. The function sub-tree includes: 

Communication Parameters

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ECC Management

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OSI Management

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Access Control

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NE ECC Link Management

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DCC Management

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IP Protocol Stack Management

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Inband DCN System Management

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Tips: You can check the communication parameters, NE ECC channels and DCC parameters when the NE communication malfunction happens caused by faulty ECC, which is helpful to allocate and solve the problem.


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You should create the protection subnet according to actual network protection demand before the service configuration.

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Protection subnet management supports protection subnet search, browse, creation and maintenance.

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In this user interface, you can maintain and manage protection subnets such as starting or stopping the MSP protocol, protection switching, or checking the protection status. There would be some slight change during the operation for different protection subnet type.

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Tips: Before MSP testing, you can perform exercise switching to check if the APS protocol can normally work.

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In the Clock View, you can create a virtual clock device, create a virtual clock link, search for clock links.

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Virtual clock devices and virtual clock links are for the third party equipments which U2000 can’t manage.

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Searching for clock links: You can search for clock links of NEs network-wide to learn the clock tracing relationships between NEs. In this function, you can specify the search scope based on the NE or clock link types, which including 1588v2, SDH, PON, Synchronous ETH.

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The broken line represents clock priority configuration, while the real link represents the current synchronization status

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In the user interface of DCN Management, you can assign the gateway NE for NEs, which ensures the DCN connectivity.

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DCN protection includes:

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Automatic switch of Gateway NE. You can assign one primary and three standby GNEs at most.

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Configure the Revertive Mode for switch.

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Configure GNE type and IP address.

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NE connectivity test.

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Query the NEs connected with the GNE in DCN management interface.

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In GNE management interface, you can take a view of GNE attributes, modify GNE IP address, and test GNE connectivity.

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NSAP (Network Service Access Point) address is used for OSI protocol while the TSAP (Transport layer Service Access Point) is the protocol port of OSI protocol.

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An NE and GNE can be converted each other.

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Cautions: The recommended number of non-gateway NEs (including non-gateway NEs that connects to the GNE by using the extended ECC) that connect to each GNE is fewer than 50. Do not connect more than 60 non-gateway NEs to a GNE.


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U2000 supports powerful E2E functions for transmission network: 

SDH E2E

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Ethernet Service E2E

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WDM E2E

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RTN E2E

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ASON E2E

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Hybrid MSTP E2E

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The E2E functions are controlled by the license file.

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The U2000 provides a powerful and flexible trail creation function for SDH, Ethernet, ATM, WDM, etc. In this SDH trail creation interface, for example, you can allocate timeslot, protection priority strategy and resource usage strategy for the service trails. The service route can also be automatically calculated by system or be manually assigned via the ‘Route Constraint’ function.

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The U2000 supports the service granularities based on VC12, VC3, VC4, VC4-4C, VC4-8C, VC4-16C, and VC4-64C. The VC4 server trail must be created before the VC12 and VC3 services configuration.

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The ‘Trail Creation’ can avoid the discrete services.

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Tips: During a new deployment of the equipment, certain alarms that are reasonable but meaninglessly occur. For example, when you configure an SDH trail without the physical connection of cables, the corresponding LOS alarm is generated. If the ‘Alarm Reversion’ is checked, the alarm will not be displayed. This does not affect the network monitoring

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

The Trail Management interface comprises four parts: part A is the table of trails, part B is the function buttons area, part C is the detailed trail route area, and Part D is the graphic area.

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In this user interface, you can set filter criteria for trail display, check the status of the service trail and correlative information, alarms or abnormal performance.

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The U2000 supports the maintenance operation based on trails, such as alarm supppression and alarm reversion, overhead bytes modification, loopback, etc. You can also export the table of trails and print out.

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Entrance: Choose Service > Tunnel > Create Tunnel from the main menu.

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OptiX equipment supports the MPLS tunnel, which is a tunneling technology using the MPLS-protocol-based encapsulation.

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Entrance: Choose Service > Tunnel > Manage Tunnel from the main menu.

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You can view the VPN service carried on a Tunnel.

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You can view the topology of a Tunnel.

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You can view the performance and alarms of a Tunnel.

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You can monitor the running status of a Tunnel.

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You can diagnose a Tunnel by performing the LSP ping and LSP tracert tests.

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Entrance: Choose Service > PWE3 Service > Create PWE3 Service from the main menu.

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You can create a CES PWE3 service tunnel for transmitting TDM signals in trail configuration mode. By using the trail configuration mode, you can directly configure the source and sink nodes of a CES service and the PW attributes on the GUI of the U2000. In this manner, the CES service can be created quickly.

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Entrance: Choose Service > PWE3 Service > Manage PWE3 Service from the main menu.

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You can view the service topology of a PWE3 service, learn the topology structure and running status of the service in real time.

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You can also monitor the performance and alarm of a PWE3 service.

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U2000V1R5 supports quick PID service configuration. 

Search and automatic creation of OCH trails

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PID service configuration

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U2000V1R5 supports quick OTN service configuration. 

Service package configuration

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Cross-layer service creation, modification and replication

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One-station configuration

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U2000V1R5 supports centralized trail maintenance.

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Centralized information displays in GUIs, including alarms, optical power, MCA spectrum analysis data, bit errors, etc

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Automatic analysis of fault location on trails, improving troubleshooting efficiency

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U2000V1R5 supports the trail configuration of ODUflex service.

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U2000V1R6 supports the trail configuration of 40G/100G coherent boards.


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In alarm management, you can monitor network exceptions in real time. It provides various management methods such as alarm statistics, alarm identification, alarm notification, alarm redefinition, and alarm correlation analysis so that the network administrator can take proper measures to recover the normal operation of the network.

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The U2000 supports the powerful fault management function which helps us for the routine maintenance, most of the operation such as fault browse, alarms synchronization, etc, are implemented by this function.

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Alarms browse is the important operation for routine maintenance.

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Choose one piece of the alarms and right click, you can check the Alarm Affected Trails and Alarm Affected Customers, you can also remove the faults with the of ‘Fault Diagnosis’ wizard.

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

In the interface of ’Fault>Settings> NE Alarm/Event Config‘, you can set alarm severity, automatic reporting, and alarm suppression status and apply an alarm attribute template to NEs, subnet and boards.



Explanation for the ‘Status’

or

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

Report: Alarm detected by NE is reported to the NMS.



Not Report: The alarm detection is still carried on by NE, but not reported to the NMS.



Suppressed: Detected alarm is suppressed and the NE does not monitor the suppressed alarm anymore.



Not suppressed: Vice versa.

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Caution: The system usually works with the default Alarm Attribute which cannot be modified, but you can modify and save it as another template and apply it to NEs, subnet and boards.


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Alarm management mainly includes the following operations: 

Customizing Alarm Template



Synchronizing Alarms



Monitoring Network Alarms



Handling an Alarm



Setting the Alarm Auto Processing



Setting the Alarm Filtering

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

Setting Audible and Visual Alarm Notification



Setting Alarm Remote Notification



Analyzing the Root Alarm of a Fault



Dumping Alarms or Events



Suppressing Alarms



Setting Alarm Reversion



Setting Automatic Alarm Reporting



Modifying Alarm Severity



Diagnosing Faults



Alarm Time Localization

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

The U2000 supports the powerful performance management function which helps us for the routine maintenance, most of the operation for alarms are implemented by this function.



Performance browse is the important operation for routine maintenance. You can check the current and history performance data, UAT events and performance threshold crossings record in the browse window, you can also select the options in the frame of ‘Performance Event Type’ to get the performance information that you expect.

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The U2000 can monitor the key indexes of a network in real time, and provide statistics on the collected performance data. It provides a graphical user interface (GUI) to facilitate network performance management.

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

Management on physical inventories, fibers and cables, fiber and cable pipes, link resources, and interface resources.



Physical Resource

or

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

Telecommunications Room



Rack



NE



Shelf



Board



Port



Slot



Fiber/Cable

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

The U2000 provides the inventory management function that allows you to query and collect statistics on physical and logical resources.



Logical Resource

or

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

Connection



Gateway



Virtual Local Area Network (VLAN)



Multicast



Quality of service (QoS) and access control list (ACL)



Protocol



Link



Link group



Interface Resource

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L e





s e c r u o s e R

Project Document 

Clock Tracing Diagram



Networking Diagram



Timeslot Allocation Diagram



Board Manufacturer Information

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For convenient information browse and management, U2000 supports the following main reports: 

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SDH Report 

Port Resource Report



Statistics Report of SDH Tributary Port Resources



Lower Order Cross-Connection Statistics Report

Microwave Report 

Microwave Link Report



Microwave License Capacity Report

WDM Statistics Report 

WDM Protection Group Switching Status Report



WDM NE Master/Slave Subrack Info Report


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The security management function includes authentication, authorization, and access control, to ensure that users can perform operations according to their respective authorities. The U2000 adopts an authority-based and domain-based security management policy, and a security mechanism including access control and encrypted text transmission. This ensures the security of the U2000 system and the transport network data.

s e c r u o s e R



Authentication Management：Support NM user authentication and NE security management.



Authority Management: Support authority management of NM user and remote maintenance user.

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

Network Security Management: Support the Security Socket Layer (SSL) protocol and encrypting the user name and password that are used to log in to an NE



System Security Management: Support monitoring system status and user login management.



Log Management: Support the log operations query and log events restoration.


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



User Management



User Group Management



Operation Set Management



Access Management



Equipment Set Management



Security Policy Management

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

Client Lockout



ACL

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Security management function

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

Database management includes the management of NE and U2000 databases. To ensure data security, you need to back up the database periodically.



MSuite is a tool for U2000 database backup, restoration or initialization.



You can backup or restore the U2000 network configuration data by importing or exporting script files through U2000 client.

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The U2000 provides SNMP, CORBA, FTP performance NBI and XML NBIs. The U2000 can be interconnected with different third-party NMSs flexibly through NBIs, to provide the information about physical inventory and alarms to the upper-layer NMSs.

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If the U2000 needs to be accessed to the upper-level network management system, the corresponding northbound interface such as CORBA, XML, and SNMP northbound interfaces should be configured.

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Answers:

// : p



NEL, EML, NML, SML, BML.



Q3, XML, SNMP, CORBA, TXT interfaces

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Ethernet Services and Networking Applications

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

1 Basic Concepts.................................................................................. Page 3



2 Ethernet Service Classification............................................................Page 9

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Reference:



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

ITU-T Recommendation G.8011/Y.1307



ITU-T Recommendation G.8010/Y.1306



ITU-T Recommendation G.7041/Y.1303 (GFP)



ITU-T Recommendation G.7042/Y.1305 (LCAS)

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The basic concepts about Ethernet over SDH (EOS) will be mentioned in chapter 1 including External port, VCTRUNK, Tag attribute etc.



s e c r u o s e R

Chapter 2 is the introduction of Ethernet service classification, the definitions, applications and related functions of Ethernet services will be described.



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For OptiX Ethernet unit, we mainly focus on L2. VLAN (Virtual local area network) is used to isolated different Ethernet signals which are carried by the same physical link, for example the same port or VCTRUNK.



s e c r u o s e R

Frame structure of IEEE 802.1Q frame (VLAN)



DA

SA

PT= 0X8100

VLAN

Ethernet Data

6

6

2

2

N

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



The protocol type (PT) of IEEE 802.1Q frame is 0X8100, it is the identification of the signal;

In two bytes VLAN label: 

Priority 3 bits, 0~8 levels;



CFI 1 bit, Token-Ring encapsulation;



VLAN ID 12 bits, the range of VLAN ID is 0~4095.


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Port is the external physical port of Ethernet unit. For example, in the front panel of EFS4 there are four external physical ports (RJ45).











s e c r u o s e R

The working modes of the FE external port are Auto-negotiation, 10Mbps (Half/Full duplex) and 100Mbps (Half/Full duplex); For GE optical port the working modes are Auto-negotiation and 1000Mbps Full duplex.

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For 10GE optical port the working modes are 10GE Full duplex LAN (10.3125 Gbit/s) and 10GE Full duplex WAN (9.953 Gbit/s).

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VCTRUNK is the logical internal port. One Ethernet unit provides several VCTRUNKs connect with XCS unit.

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



VCTRUNK is built by VC (virtual container), for example if we bind five VC12 into one VCTRUNK the rate of SDH side is around 10Mbps (2Mbps*5); Normally virtual concatenation (VCAT) technology is used to bind VC into VCTRUNK. VCAT is much more flexible than contiguous concatenation (CCAT), all of the members’ status can be monitored by Ethernet unit. If some of the members are failed, the LCAS (link Capacity Adjustment Scheme) function executes the bandwidth adjustment immediately without service interruption, however CCAT can not provide this function, all of the bandwidth will be unavailable when member failure in one group.


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FE or GE signal is accessed by external port then the GFP-F encapsulation protocol will adopt the Ethernet signal to VCTRUNK.

s e c r u o s e R

Two types of GFP encapsulation protocols: 

GFP-F (Frame-mapped GFP)



For Ethernet service, e.g. FE/GE. GFP-T (Transparent GFP) 

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For SAN (Storage Area Network) service, e.g. ESCON/FICON/Fiber channel. Both of the external and internal ports can process Tag flag. 



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

All of the EFGS series boards can process the Tag flag.



Tag flag is used to identify the type of frames:

s e c r u o s e R



Tag frame: Signal contains VLAN;



Untag frame: Signal doesn’t contain VLAN.

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The VLAN ID of the frame accessed from the external port is 10, please fill the blanks. If the frame doesn’t contain VLAN ID please fill with “-”.



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Most of the Ethernet boards provide three types of tag attributes: Tag aware, Access and Hybrid. But some of the boards in Metro series can not provide Hybrid, e.g. ET1.

 Thought:

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Board Port

Port types

VCTRUNK

Port Tag attribute

EFS0

Access

EFS4

Tag

Board

②

①

Hybrid

VCTRUNK PVID

Tag attribute

PVID

11

Access

12

Access

12

Hybrid

10

Hybrid

12

10

①’s VID

EGS2 Tag


②’s VID

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From ITU-T recommendation:



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

EPL: Ethernet Private Line



Feature: Point to point transmission without sharing. EVPL: Ethernet Virtual Private Line



Feature: Point to point transmission with port or VCTRUNK sharing. EPLAN: Ethernet Private LAN





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Feature: Multi-points to multi-points transmission without sharing, based on L2 switching. EVPLAN: Ethernet Virtual Private Line 

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





Feature: Multi-points to multi-points transmission with port or VCTRUNK sharing, based on L2 switching; Bandwidth utilization ratio is low.


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In the case of EPL services, a bandwidth is exclusively occupied by the service of a user and the services of different users are isolated. In addition, the extra QoS scheme and security scheme are not required.



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Services A & B access with different external ports then cross-connect to different VCTRUNKs.



s e c r u o s e R

Point to point transmission without sharing, it provides the low latency and high security point to point transmission.



The bandwidth for customers can be guaranteed, the max. bandwidth of point to point EPL depends on the bandwidth of VCTRUNK.



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Application: Private line for VIP user for example bank and government private line.



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If the resource of port or Vctrunk is not enough, different users should share the same port or Vctrunk. Hence, VLAN ID division/MPLS/QinQ technology should be adopted to isolate different services.



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In ITU-T the “V” of EVPL stands for sharing. Share the external port or VCTRUNK with different VLAN ID, MPLS label or S-VLAN.



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Services access by NE 1will be transmitted by the same external port then cross-connect to different VCTRUNKs, these two services are isolated with different VLAN ID.



s e c r u o s e R

Different customers occupy different VCTRUNK, the bandwidth of VCTRUNK can be guaranteed.



More than one customers share with one external port, so we should control the bandwidth allocation of this external port.



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

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Service which is from the headquarters have to be transmitted to different department.



M

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

For example two customers share with one FE port, if one customer use 90% bandwidth of the FE port then another one just can use 10%. Normally we use CAR (Committed Access Rate) function to solve the problem. We can manually configure the committed information rate (CIR) for each of customer.

Application: the quantity of external port is limited, if the external ports are not enough then we can try to implement the port shared EVPL service.


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Different customers occupy different external ports, the bandwidth of external port can be guaranteed.



More than one customers share with one VCTRUNK, so we should control the bandwidth allocation of this VCTRUNK.





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For example two customers share with one VCTRUNK, if one customer use 90% bandwidth of this VCTRUNK then another one just can use 10%.

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Services A & B access with different external ports then cross-connect to the same VCTRUNKs, these two services are isolated with different VLAN ID in the same VCTRUNK.



M

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

Normally we use CAR (Committed Access Rate) function to control the rate of external port. We can manually configure the committed information rate (CIR) for each of customer.

Application: the max. bandwidth of VCTRUNK is limited, if the total bandwidth is not enough then the VCTRUNK shared EVPL can be used (Different users should have different VLAN ID).


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

MartinioE Format SA

0x8847(0x8848 broadcast)

Tunnel

VC

Ethernet Data

6

6

2

4

4

N



For the MartinoE encapsulation protocol totally 22 bytes add to the original frame;



The value of protocol type is 0x8847 for MPLS, this is the indication of MPLS;

M

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Totally there are two labels in one MatinoE frame, Tunnel and VC, each of them is 4 bytes. In the tunnel and VC there are 20 bits used as the label function. So the available range of label is 16~(220-1), 0~15 is reserved by the system.

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DA





t t :h

The frame structure of MPLS:

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The port attribute of MPLS is P or PE: 

PE: the edge of MPLS network, it is used to access the signal without MPLS;



P: the internal port of MPLS network;



The operation of PE and P ports: 

PE->P (Ingress): Add MPLS label;



P->PE (Egress): Discard MPLS label;



P->P (Transit): Exchange MPLS label.


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When we configure the EVPL (MPLS) service, the default MPLS encapsulation is MartinoE. It provides two stackable labels Tunnel and VC;



s e c r u o s e R

Different values of VC and Tunnel are used to isolate several Ethernet signal with the same VLAN ID.



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QinQ technology is a VLAN stacking technology, which conforms to the recommendation for S-VLAN in IEEE 802.1ad and is an expansion of VLAN technology.



s e c r u o s e R

Advantages of QinQ technology:







Expands VLAN and alleviates VLAN resource insufficiency. For example, a VLAN providing 4096 VLAN IDs can provide 4096 x 4096 VLANs after VLAN stacking; Extends LAN service to WAN, connecting the client network to the carrier network and supporting transparent transmission.

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QinQ frame format:



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DA

SA

TYPE(8100)

S-VLAN

TYPE(8100)

C-VLAN

Ethernet

(6B)

(6B)

(2B)

(2B)

(2B)

(2B)

Data



Customer VLAN label, defined as C-VLAN;



Server layer VLAN label, defined as S-VLAN.


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From NE1 to NE2, traffic flow from Dept.A and Dept.B with the same C-VLAN-100, two different S-VLAN be attached on the two access ports of NE1 separately, hence, the two traffic flows can be transported in the same channel, on the destination site NE2, the two

s e c r u o s e R

S-VLAN tag be unloaded, to recover the original traffic.

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EPLAN service can provide multi-point to multi-point transmission without sharing.



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

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If NE3’s VB is failed, what will happen to the EPLAN service?

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

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EPLAN is based on L2 switching, so in NE2, 3, 4 we should manually configure the VB (Virtual bridge), it is the logical L2 lanswitch. So the traffic between NE2 and NE4 will be forwarded by this VB, and it’s no need to configure the point to point VCTRUNK between NE2 to NE4 any more. Also this solution can increase the bandwidth utilization ratio. Compared with EPL service we need less point to point VCTRUNKs.

 Thought:

or

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

If NE3’s VB is failed, then the LAN service will be interrupted, the VB in NE3 can not forward the data any more. Normally we should configure another backup VB to prevent the VB failure. For example we could configure a backup VB in NE1, and if NE3’s VB is failed the traffic can still go through with NE1’s VB. However, there is another problem which is called “Broadcast storm”. After we configure 2 VBs in different NEs then loop occurs. STP (Spanning Three Protocol) is used to solve this problem.


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VB is the logical L2 switch, it provides MAC address self-learning function. MAC address self-learning function obviously improves the data forwarding efficiency. How? 

s e c r u o s e R

There is a CAM table in the L2 switch. Initially the CAM table is empty, when the port of L2 switch receives the frame it will broadcast the frame to all the other ports, at the same time it records the source MAC address of the frame into the CAM table. The CAM table records the relation between MAC address and port No.;

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After the relation of MAC address and port is established, and the L2 switch will forward frames based on the destination address.

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The working mechanism of VB is the same as L2 switch, the ports of this logical L2 switch are called LP.

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



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The spanning tree protocol (STP) blocks certain ports to avoid the loop. Hence, this can solve problems.

s e c r u o s e R

In addition, after being enabled, the STP logically modifies the network topology structure to avoid broadcast storms.

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EVPLAN Service can provide multi-point to multi-point transmission with sharing. In order to identify data from different users, VLAN/MPLS/QinQ technology should be adopted.

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The MAC address self-learning and data forwarding of EPLAN service will be based on VB + MAC address. It’s no need to configure the VLAN filter table.

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UNI port type of SVL VB: Tag Aware and Access

EVPLAN service forwards data through VB + MAC Address + VLAN/S-VLAN. The VLAN filter table is necessary.

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UNI port type of IVL VB: Tag Aware, Access and Hybrid

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Ingress Filtering:

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Enabled: The ingress filtering depends on the setting of the bridge switching mode. When the bridge switching mode is set to IVL/Enable Ingress Filtering, the ingress filtering is jointly enabled. Disabled: The ingress filtering depends on the setting of the bridge switching mode. When the bridge switching mode is set to SVL/Disable Ingress Filtering, the ingress filtering is jointly disabled.


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The configuration of EVPLAN (802.1q) service is quite similar with EPLAN service. The only difference is the VLAN filter table is necessary in EVPLAN (802.1q) service.

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IEEE 802.1q bridge supports isolation by using one layer of VLAN tags. It checks the contents of the VLAN tags that are in the data frames and performs Layer 2 switching according to the destination MAC addresses and VLAN IDs.

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In NE 3, the LPs of VB is port 1, port 2, VCTRUNK 1 and VCTRUNK 2. Data forwarding will be based on different VLAN ID.

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Is it necessary to configure VB in NE 2 and NE 4? If no, what kind of service should be configured in these two stations?

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The IEEE 802.1ad bridge supports data frames with two layers of VLAN tags. It adopts the outer S-VLAN tags to isolate different VLANs and supports only the mounted ports whose attributes are C-Aware or S-Aware. This bridge supports the following switching modes:

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This bridge does not check the contents of the VLAN tags that are in the packets and performs Layer 2 switching according to the destination MAC addresses of the packets.

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This bridge checks the contents of the VLAN tags that are in the packets and performs Layer 2 switching according to the destination MAC addresses and the SVLAN IDs of the packets.

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In this case, the VoIP services need to be isolated from the HSI services. User M does not need to communicate with user N. Since the C-VLAN of VoIP and HIS service from user M and user N are the same, different S-VLAN should be assigned to isolated the services.


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Thank you!

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The privilege of HCNA/HCNP/HCIE: With any Huawei Career Certification, you have the privilege on http://learning.huawei.com/en to enjoy: 

1、e-Learning Courses： Logon http://learning.huawei.com/en and enter Huawei Training/e-Learning 

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

If you have the HCIE certificate: You can access all the e-Learning courses which marked for HCIE Certification Users.



Methods to get the HCIE e-Learning privilege : Please associate HCIE certificate information with your Huawei account, and

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email the account to [email protected] to apply for HCIE e-Learning privilege.

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2、 Training Material Download 

Content: Huawei product training material and Huawei career certification training material.



Method：Logon http://learning.huawei.com/en and enter Huawei Training/Classroom Training ,then you can download training material in the specific training introduction page.



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If you have the HCNA/HCNP certificate：You can access Huawei Career Certification and Basic Technology e-Learning courses.



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3、 Priority to participate in Huawei Online Open Class (LVC) 

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The Huawei career certification training and product training covering all ICT technical domains like R&S, UC&C, Security,

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Storage and so on, which are conducted by Huawei professional instructors. 



4、Learning Tools:

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

eNSP ：Simulate single Router&Switch device and large network.



WLAN Planner ：Network planning tools for WLAN AP products.

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In addition, Huawei has built up Huawei Technical Forum which allows candidates to discuss technical issues with Huawei experts , share exam experiences with others or be acquainted with Huawei Products.

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Statement:

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This material is for personal use only, and can not be used by any individual or organization for any commercial purposes.

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HUAWEI TECHNOLOGIES CO., LTD.

Huawei Confidential

1

HCNA-Transmission Training Material

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