SDH

SDHBasics

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overviewMultiplexing techniques are used to enhance the performance of a transmission network by increasing the number of signal connections those can be held at the same time.SDH is an attractive TDM technologyDefined by the ITUA compatible technology is the Synchronous Optical Network (SONET) by the ANSI

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PCM 30payload channels: 30 - Rate per channel: 64 kbps - Frame data rate: 2.048 Mbps30 payload channels each with a rate of 64 kb/s are byte by byte multiplexed to generate a signal with a rate of 2.048 Mb/s.

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PCM FrameCapacity: 256 bitsPayload data: 240 bitsSignaling information: 16 bits

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Higher level multiplexing To carry multiple PCM30 signals on a trunk, multiplexing is applied.Some stuffing bits are added to match the levels.

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Plesiochronous multiplexing hierarchy

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PDH Disadvantagesmultiple rates at the same hierarchy level. To extract a lower level signal from a higher level one, demultiplexing is needed many times. The same action is needed on the reverse direction.PDH also lacks standards on international boarders.i.e. PDH lacks flexibility.The solution to these problems was the Synchronous Digital Hierarchy ( SDH ).

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SDH Features (1)ITU-T Standard: Recommendation G707. World wide standard ( international ). Synchronous TDM Technology.Standard interfaces ( different vendor compatibility ). High operating capabilities: path performance monitoring, communications channels, auxiliary channels.

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SDH Features (2)Direct tributary channel access: single multiplexing stage, ease of Add and Drop, flexible networks, 1 step Mux/DemuxManagement and protection Optical Transmission: Performance and high capacity. Very high rates Compatibility with current PDH networks.

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SDH Features:Direct Access

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SDH: Cost Benefitsequipment levelDirect tributary channel access. Multiplexer and line terminal functions in one equipment unit. network levelNetworking ease. Operational flexibilityservices levelVarious bit rates on one route. Traffic management. On-Demand services.

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SDH : ApplicationsSpeech / Data / Video. Multimedia communications. Fast data interchange. LAN interconnections. Broadband ISDN.ATM.EthernetDLC

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PDH networks integration in SDH

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SDH ratesOne byte rate is 8 / 125 s = 64 kbpsSTM-1 = 155.520 Mbps, around 1890 TSSTM-4 = 620 Mbps, 8000 TSSTM-16 = 2.48 Gbps, 30000 TSSTM-64 = 10 Gbps, 120000 TSWDM: several signals are sent on the same optical beam, but with different wavelengthsn x STM-m ( m=1,4,16,64, . . ), n=8,64,..e.g 8 x STM-64=> 1 million TS

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SDH Processes: MappingExisting PDH networks can be integrated in a synchronous network. This is possible through the packing of the PDH signals into defined size SDH structures called containers.A container has a fixed size, which is a great advantage of SDH This process is called mapping.

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From user information to SDHThe user information is mapped in a container ( C ) of a suitable size. Some control information ( Path Over Head : POH ) is added to generate a virtual container ( VC ). A Pointer is added to the VC to generate a Tributary Unit ( TU ).

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From user information to SDHmultiplexing of many TUs results in a Tributary Unit Group ( TUG ).Multiplexing of TUGs generates an Administrative Unit ( AU ). Further more, multiplexing AUs results in an Administrative Unit Group ( AUG ). Finally some control information ( Section Over Head : SOH ) is added to generate the SDH frame: Synchronous Transport Module ( STM ).

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ITU

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From user information to SDHHO VC + PTR = AU .LO VC + PTR = TU .Synchronization results from the addition of a pointer. So : C or VC may not be synchronized with the STM frame, while a TU, TUG, AU or AUG is synchronous. The VCs are put inside the TUs so as to resynchronize them to each other, and the pointer is added to localise the VC inside the TUAn ATM cell can be mapped in a VC2, VC3 or VC4.

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SynchronizationtTUTUTUVCVCVCdtpointer

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SDH SignalsDifferent levels of STM are defined:STM-1 : STM level one, with a rate of 155.520 Mb/s.STM-1 rate= 2430 bytes x 8 bits / 125 sSTM-4 : STM level four, 622 Mb/s.STM-16 : STM level sixteen, 2.4 Gb/s.STM-64 : STM level sixty four, 10 Gb/s.Each time multiplexing four STM signals generates the higher level STM-N.

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SDH: Frame Structure (1)

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Synchronous STM-N multiplexingThe payload is the multiplexed payloads. The pointer is the multiplexed pointers. The SOH is not the multiplexed SOHs, it is a new generated SOH ( some SOH bytes are identical some are different ), it is 4 x SOHs in size only. It is composed of signals special for the desired STM-N Multiplexing is byte per byte.

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SDH: Network Sections

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Network ElementsNERepeater/RegeneratorADMCross ConnectTMGateway NE

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Network - exampleETHCommunication channels are provided between: - The Element Manager and the GNE via an Ethernet LAN via the Q interface provided by the COMM card. - The GNE and the other NEs via the DCC channels.

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Section OverheadSubscriber generates the information signal. The NE generates the STM signal. RSOH: analyzed in each RS and MS. MSOH: goes transparently in repeaters and analyzed only in MS end NEs. SOH: Supervision of the carried SDH signal.

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RSOH bytes

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RSOH: FunctionsIf no transition A1/A2 on one frame, OOF alarm ( out of frame )In OOF states for 3 ms, LOF ( loss of frame )In OOF state for 60 ms, LOS ( loss of signal )C1: STM identifier, defines the position of each STM-1 signal in an STM-N frame. e.g. 4 STM-1 signals within an STM-4 signal ( C1=1:S1, C1=2: S2, ..).B1: BIP ( Bit Interleaved Parity check ): for each frame parity calculation is done, the result is stored in the B1 byte of the next frame ( compared at RX ).

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RSOH: FunctionsE1: Service channel, speech signal ( EOW ). F1: Speech and data signals for privilege users e.g. network administrator. D1 D2 D3: Data Communication Channels (DCC) ,control and monitoring of NEs. These channels are used to transmit commands from the management to the equipments and alarms and reports from the NEs to the management system.

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RSOH: E1Service channel, speech signal ( EOW )

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RSOH: F1

Speech and data signals for privilege users e.g. network administrator.

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MSOH BYTES

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MSOH ( continued ) B2B2B2: BIP 24; quality alarmsIf Er >= 10-6 , MS-SD: MS-REI ( in M1 )If Er >= 10-3 , MS-EBER: MS-RDI ( in K2 )MSP 1+1: multiplex section protection, with one main and one standby; a feature processed by the APS mechanismLast 3 bits of K2:111: MS-AIS110: MS-RDIK1 and the first 5 bits of K2: used for the APS in a case of an MSP

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APS example (1):Traffic flows from A to D via C

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APS example (2)line A-C interrupted, C sends message in bytes K1,K2 to A.

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APS example (3)A receives K1,K2 an automatic switching occurs: Data flows from A to D via B.

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Path Over Head ( POH )Additional information to guarantee the signal across the SDH network contains operating, monitoring and control information related to the signal path from its source to its destination. Contains: quality measurements based on parity calculationParity is calculated at Rx and compared with that calculated at TxREI or FEBE: parity error, qualityRDI or FERF: complete failure

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POH ( continued )POH holds the supervision of the PDH carried signal PDHPDHPOH insertionPOH extraction and analysisSDH networkTransport Network

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ParityTxRxSDHVCVCV5V5V5V5P1 P2P1* P2*

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ParityP1: the parity value ( odd or even ) for the odd bits of all the bytes of the VCP2: the parity value ( odd or even ) for the even bits of all the bytes of the VCAt Rx, compare P1 with P1* & P2 with P2*If they are not the same, an error is indicated, and computalization performed

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computalizationComputalization of the error in performance registersThen, quality alarms:If Er >= 10-n , 5

VC4/3 POH: 9 bytes.

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VC4/3 POH: 9 bytes. J1: the NE that generates the VC put the information about the path identity in the J1 byte. The desired VC is assigned a name which defines the path of this VC. In case of failure, an alarm: path trace failure is generatedC2: describes the payload content ( if it is an ATM cell, C2 = 13, empty, C2 = 0, . )B3: the parity is calculated for the first bit in each byte, the same is done for the second bit, the third, and on till the 8th. The 8 results are transmitted in B3 and analyzed at Rx.G1: if A is bi-directionally connected to B, and the line from A to B is cut, B sends on G1 a Far End Receive Failure ( FERF ) error message to A.F2: user channel, a communication channel accessed only at the source and destination NEs of the VC. Used for management message transmission

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VC4/3 POH ( continued ) H4: multi frame indicatorH4= 0000, V1H4= 0001, V2H4= 00010, V3H4= 00011, V4In case of error, HO-LOM alarm generatedLOM: loss of multiframe

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VC-12 POH

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VC-12 POHIf a multi frame is used, V5 appears only in the first VC 12.If a parity error is detected on bits 1&2 ,a FEBE is located on bit 3.Signal label defines the payload type.

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Pointerneeded because the clock of the incoming data to an SDH NE may differ from the output clock.VCs shifts within the STM-1 frame during the synchronization process.The VC4 may not be at the same position of the payload area of the STM-1 frame. The AU-4 pointer holds the address of the beginning of the VC4. It contains nine bytes H1H1H1H2H2H2H3H3H3 where H1,H2 : pointer value and H3: justification.Pointer value composed of 10 bits: 1024 possible valuesVC-4: 2340 bytes ( cannot be addressed with 10 bits only )Solution: address values taken in 3 bytes steps, from 0 to 782 ( 2430 / 3 )

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AU-4 PointerDynamic VC-4 justification

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AU-4 Pointer ( cont )If the first VC begins at location n, then the first pointer value will be n and also the value of all pointersValid reasons for different pointer values:The NDF is validated, in case of transfer from a signal to anotherDesynchronization: justification is usedIf it is changed for another reason: AU-LOP alarmIf H1=H2= 111, alarm: AU-AIS

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Positive justification Justification takes place during mappingIf fin > fout : 3 stuffing bytes are appended to the pointer. The new pointer value will be = old value + 1.

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Positive justification

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Negative justificationfin < fout : H3 bytes are padded with payload data . The new pointer value will be = old value 1 The pointer value must be maintained at least for two STM-1 frames.

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Negative justification

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NPINull Pointer IndicatorUsed to indicate when a TUG-2 structure is being carried, rather than a TU-3 with its associated TU-3 pointer.i.e., their location in the SDH frame may handle either the NPI if TUG-2 is used or a pointer if TU-3 is there

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SystemsLine systemsCross ConnectAdd Drop Multiplexer ( ADM )

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Line SystemsPoint to point linkTrib sideLine sideFOTTribSideLine Side

STM n

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Wireless Microwave equipmentIn: wired STM-1Out: wireless STM-1STM - 1STM - 1SDH

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Cross ConnectExpensiveMainly to cross connect STM-1 lines34140STM-134140STM-1

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ADMAdd Drop MuxLower level insertion / extraction Line westLine EastTrib Side

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LAN connectionEthernetEthernetTMTMSDHSTM - 1

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SDH & WDMSDHSDHSDHSDHSDHSDHSDHSDHFiberLines rate is STM-161234WDMWDMSDHSDH

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NotesAn equipment must not be put off If for any reason, it is to be put off, a right order must be followed Switch Plane ProtectionPlug in order: first link, second routerPlug out order: first router, then linkFor Tx/Rx STM-16 boardPlug in order: mux, then Tx or RX cardPlug out order: Tx or RX card then the MuxThe MUX adds a pointer to every input VC4, hence producing the AU4, henceMUX function: resynchronization onlyMuxing takes place in the OIC

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Protection/Restoration MechanismsLinear Multiplex Section Protection (1+1 or n:1) (MSP)Subnetwork Connection Protection (SNCP) - Fiber RingsMS Shared Protection Rings (MS-SPRings) - Self-Healing Rings

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Protection Mechanisms (I)Multiplex Section 1:N Protection (shared)Multiplex Section 1+1 Protection (dedicated)Multiplex Section Shared Protection RingsMultiplex Section Dedicated Pro- tection RingsSubnetwork Connection Protection Rings (Fiber Rings)Multiplex Section 1+1 Protection (dedicated)Connection-orientedMultiplex-section-orientedPDHSDHTrail ProtectionSubnetwork Connection ProtectionLinear Multiplex Section ProtectionMultiplex Section Protection Rings

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Protection Mechanisms (II)Connection-orientedmechanisms of bridging and switching between a working and a protection connection (1+1) at source and destinationProtected: connections protected by SNCP = 100% redundancy Unprotected: connections not protected by SNCP Multiplex-section-oriented'local' linear and ring protection mechanismslocal facilities to protect connections independently on whether they are protected in a connection-oriented manner or notwidely used: self-healing rings

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MXA 16STM-162M2MAnalysis pointSNC protection - 1

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SNC protection - 1At the defined point, the following processes done:1 analyze SOHSTM16 FAW(LOS,LOF), K2(MS-AIS, MS-RDI), M1(MS-REI), B2(MS-SD, MS-EBER) 2 demux into 16 AU43 for 4 AU4 ( fully switched )3.1 pointer analysis (H1,H2): AU-LOP, AU-AIS3.2 POHVC4 analysis: G1(HO-REI, HO-RDI), B3(HO-EBER, HO-SD), C2(VC-unequiped), H4(HO-LOM)3.3 TU12 pointer analysis: TU-LOP/TU-AIS3.4 VC12 POH analysis: TU-EBER/TU-SDSteps 1,2,3: quality information for each VC12 ( O.K, SD, or SF)All this analysis is done in the STM-16 Rx OIC ( SOH ) and the associated Mux card

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SNC protection - 3Depending on the quality measurement done above, the signal is assigned O.K, SD, or SF. As a result, the switch will choose the better oneAfter choosing the signal, and hence switching to the standby directionRevertive mode: after maintenance of the main, the switch will switch back to the main. A timer must be set: WTR (0~30)min ( default is 10 )Non-Revertive: to stay on the standby and not to return backUnidirectional or Bidirectional on RFI, bit 4 of V5Uni: switch on the corrupted side onlyBi: switch on both sides ( corrupted and remote )WTR: wait time to restoreNon-Revertive: best

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1:N trib card protectionFor MXA 16, there are 8 cards ( NB tribs )The 9th card is used for protection where only a 2M card can be pluggedSo, slots 1~8 for tribs, slot 9 for protectionThe 2M protection slot can not be used for any level other than 2M, henceFor 34,45 or 140, one of the 8 trib slots is used for protectionThe last right free card is used to protect all the required ( 34, 45, or 140 ) to the left of itIt is possible to put a protection card for 34, another for 45, and another for 140. Only insert the desired card in the last right free slot of the 8 trib slots and configure it as protection

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SynchronizationWest lineSystem( swith + trib )East lineRx TBTx TBRx TBTx TBSys clockSys TB********MXASTM - 16STM - 16STM - 16STM - 16Ref 1Ref 2Ref 3

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SynchronizationFree running: local oscillatorSynchronization Equipment Timing Generation ( SETG )Single SETG: Ref1 = Ref2 = Ref3Multiple SETG: Ref1 Ref2 Ref3Revertive (WTR), or Non-Revertive It is better to be in revertiveTiming marker: managing quality of synchronization. For ring networks, better to be disabled

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SETGRef1 = Ref2 = Ref3P: priority level to be setSee next diagram

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destinationsourceEquip clockExternal outgoingWest A1West A2West B1West B2 ( Rx TB )PPEast A1East A2East B1East B2 ( Rx TB )PPExt / tribPSASE clockPEqpt clockP

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Synch. Example - 1DCABWEWWWEEEExt Clock2M :ex. Trib6, port9Synch mode: single SETG1,2,..: priority levelRule: in ring nets, W must be connected to E & E to W

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Synch. Example- 2 DCABWEWWWEEEExt Clock2M :ex. Trib6, port9Synch mode: multiple SETG1,2,..: priority levelProcess: W must be synch by E & E by W

Ext 1Ext2Trib1---2

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Synch. Example 2 ( cont )ABCD

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Addressing: exampleNSAPNSAPIONOSEthernetNSAP &Ethernet

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AddressingNSAPManual area address (sub-network address or address domain )System IDNSAP selectorEthernet address6 bytesTwo parts: IEEE & user partFor the gateway only, an Ethernet address must be configured ( Ethernet = sys ID )

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Addressing Manual area addressSystem IDNSAP selectorNSAP formatIEEEUser partEthernet formatAFIIDIHODSPDOMAIN ( e.g. SAGEM ) ID

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Addressing AFI: address code, e.g. 37 or 39First part of the IDI: country code, e.g. 208 for FranceHODSP+DOMAIN ID: subnetwork, e.g. 2001EthernetIEEE: e.g. 008002 for SAGEMUser part: e.g. 100001 Example: 37-208-11234567890-2001

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Equipment Configuration StepsCard declarationSynchronization configurationCheck & solution of card alarms in order:Controller cardLine cards ( west/east )Trib cardsSwitch cardsComms cardsCreate connections: should be done by IONOS, but can be done by LCTGive an address to the equipment for IONOS managementProtection declaration is included in the above steps

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LCTCommissioning Local / Remote Access

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Trib TestAt NE1Put a test equipment on Trib x, port yPut off the PRBSAt NE2Put off the PRBSCreate an inward loop at trib n, port mLoopsOutward: local loop; only tests the cable or link between the NEs and exchangeInward: remote loop; tests the trib port, shelf, fiber, i.e, the whole link from the local port to the remote exchange

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Un acknRed Green acknWhite clearMagnetaBlockedO.KWheatOK wheat This state means that the problem disappears without any action Of you, so the system informs you that there was a problem but it is cleared now

Disappearance of an ackno. alarm State : Color : Alarm disap.Acknowledgement Alarm Flow 1- Localization 2- Analysis3- Start solving Process. Only after this you can acknowledge the alarm Alarm disappearance without an ackno.

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Network communicationSDH NEs communicate with the Management System according to the OSI model.only the first four layers are implemented in each NE. Each NE has a unique Network Service Access Point ( NSAP ) address.

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SDH Equipment ( ADM )Line cards ( STM-N : Opt./Elec. ) connects to the network (East & West)Trib cards ( STM-N:opt./elect. , E4, E3, E1)Switching cards ( routing, cross connection)Comms card ( network communication ) Controller card ( Heart ).PSUs.AUX cards.

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2M TrProtection High band Trib (8) STM1 8STM1 84 STM-14 STM-14 STM-1 4 STM-1STM 16STM 16STM 16STM 164STM14STM14STM14STM14STM14STM14STM14STM1East Line West Line 8 STM1 by pass Link B Link A MuxingResynchronization Not muxing Adding pointer to VC4 to produce AU4Link + Router = Switch B: Protection PSUAPSUCPSUBAUXcardCOMSMUXCtrl VC4 only VC12,VC3,VC4 STM1,STM4,140MMXA 16C:-

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TxOICSTM16

TxOICSTM16

RxOICSTM16

RxOICSTM16

M U X

M U X

M U X

M U X

SONETSynchronous Optical Network.Optical Transmission Interface proposed by Bell Core and standardized by ANSI.STS-N: Synchronous Transport Signal NOC-N : Optical Carrier level N

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SONET Frame Format

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SONET STS-1 Overhead Octets

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SONET: data ratesSTS-1 / OC-151.84 MbpsSTS-3 / OC-3155.52 MbpsSTS-9 / OC-9466.56 MbpsSTS-12 / OC-12622 MbpsSTS-18 / OC-18, 24, 36, 48, 96,STS-192/OC-19210 Gbps

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SDH/SONET & NGN (1)SONET/SDH development was originally driven by the need to transport multiple PDH signals like E1, and E3 along with other groups of multiplexed DS-0 (64 kbps) PCM voice traffic. The ability to transport ATM traffic was another early application. In order to support large ATM bandwidths, the technique of concatenation was developed, whereby smaller SONET/SDH multiplexing containers (eg, STS-1) are inversely multiplexed to build up a larger container (eg, STS-3c) to support large data-oriented pipes. SONET/SDH is therefore able to transport both voice and data simultaneously.One problem with traditional concatenation, however, is inflexibility. Depending on the data and voice traffic mix that must be carried, there can be a large amount of unused bandwidth left over, due to the fixed sizes of concatenated containers. For example, fitting a 100 Mbit/s Fast Ethernet connection inside a 155 Mbit/s STS-3c container leads to considerable waste.

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SDH/SONET & NGN (2)Virtual Concatenation (VCAT) allows for a more arbitrary assembly of lower order multiplexing containers, building larger containers of fairly arbitrary size (e.g. 100 Mbit/s) without the need for intermediate SDH/SONET NEs to support this particular form of concatenation. VCAT increasingly leverages X.86 or Generic Framing Procedure (GFP) protocols in order to map payloads of arbitrary bandwidth into the virtually concatenated container.Link Capacity Adjustment Scheme (LCAS) allows for dynamically changing the bandwidth via dynamic virtual concatenation, multiplexing containers based on the short-term bandwidth needs in the network.The set of next generation SONET/SDH protocols to enable Ethernet transport is referred to as Ethernet over SONET/SDH (EoS)

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G.709ITU-T standardized method for transparent transport of services over optical wavelengths in DWDM systems. It also known as Optical Transport Hierarchy (OTH) standardUnlike SDH/SONET, the line rate is increased by maintaining the G.709 frame structure (4 rows x 4080 columns) and decreasing the frame period (in SDH/SONET the frame structure is increased and the frame period of 125 s is maintained).

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ASTNAutomatic Switched Transport Network allows traffic paths to be set up through a switched network automatically. The term ASTN replaces the term ASON (Automatically Switched Optical Network) and is often used interchangeably with GMPLS (Generalized MPLS). This is not completely correct as GMPLS is a family of protocols and ASON/ASTN an optical network that relies on GMPLS and adds more protocols to extend the protocol suite. Furthermore, the GMPLS protocols are applicable to optical and non-optical (e.g., packet and frame) networks, and can be used in transport or client networks. Thus, GMPLS is a wider concept than ASTN.ASTN allows the user to specify the start point, end point and bandwidth required, and the ASTN agent on the Network Elements will allocate the path through the network, provisioning the traffic path, setting up cross-connects, and allocating bandwidth from the paths for the user requested service. The actual path that the traffic will take through the network is not specified by the user.Changes to the network (adding/removing nodes) will be taken into account by the ASTN agents in the network, but do not need to be considered by the user

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SDH