《光纖通信課程設(shè)計(jì)》課件：SONET-rev1

AcrashcourseofSDH

Background(analogtelephony,TDM,PDH)SONET/SDHhistoryandmotivationArchitecture(path,line,section)RatesandframestructurePayloadsandmappingsProtectionandringsVCATandLCASHandlingpacketdataOutlineBackgroundThePSTNcirca1900pairofcopperwires“l(fā)ocalloop”manualroutingatlocalexchangeoffice(CO)Analogvoltagetravelsovercopperwireend-to-endVoicesignalarrivesatdestinationseverelyattenuatedanddistortedRoutingperformedmanuallyatexchangesoffice(s)RoutingisexpensiveandlengthyoperationRouteismaintainedfordurationofcallTelephonyMultiplexing1900:25%oftelephonyrevenueswenttocopperminesstandardwas18gauge,longdistanceevenheaviertwowiresperlooptocombatcross-talkneededmethodtoplacemultipleconversationsonasingletrunk1918:“Carriersystem”(FDM)5conversationsonsingletrunklaterextendedto12(group)stilllatersupergroups(60),mastergroups(60)),…fchannels8kHz12kHz4kHz16kHz20kHzTheDigitalizationofthePSTNShannon(BellLabs)provedthatDigitalcommunicationsisalways

betterthanAnalogcommunicationsandthePSTNbecamedigitalBettermeansMoreefficientuseofresources(e.g.morechannelsontrunks)Highervoicequality(lessnoise,lessdistortion)AddedfeaturesAftertheinventionofthetransistor,in1963T-carriersystem(TDM)1bytepersample–8000samplespersecondT1=24conversationspertrunk2groupspercable!ttimeslotsandswitchingbecameeasiertooComplexityincreasesrapidlywithsize124567831234567AnalogCrossbarswitchDigitalCross-connect(DXC)processort12345t21543OptimizedTelephonyRoutingCircuitswitching(routeismaintainedfordurationofcall)Route“set-up”isanexpensiveoperation,justasitwasformanualswitchingToday,complexleastcostroutingalgorithmsareusedCalldurationconsistsofset-up,voiceandtear-downphasesThePSTN(PublicSwitchedTelephoneNetwork)circa1960localloopsubscriberlineautomaticroutingthroughuniversaltelephonenetwork

Analogvoltagesusedthroughout,butextensiveFrequencyDivisionMultiplexingVoicesignalarrivesatdestinationafteramplificationandfilteringto4KHzAutomaticroutingUniversaldial-toneVoltageandtonesignalingCircuitswitching(routeismaintainedfordurationofcall)trunkscircuitsThePresentPSTNsubscriberline

Analogvoltagesandcopperwireusedonlyin“l(fā)astmile”,butcoredesignedtomimicoriginalsituationVoicesignalfilteredto4KHzatinputtodigitalnetwork

TimeDivisionMultiplexingofdigitalsignalsinthenetworkExtensiveuseoffiberopticandwirelessphysicallinksT1/E1,PDHandSONET/SDH“synchronous”protocolsSignalingcanbechannel/trunkassociatedorviaseparatenetwork(SS7)AutomaticroutingCircuitswitching(routeismaintainedfordurationofcall)Complexroutingoptimizationalgorithms(LP,Karmarkar,etc)PSTNNetworkclass5switchclass5switchtandemswitchlastmileTDMtimingTimeDomainMultiplexingreliesonallchannels(timeslots)havingpreciselythesametiming(frequencyandphase)InordertoenforcethistheTDMdeviceitselffrequentlyperformsthedigitizationanalogsignalsdigitalsignalsiftheinputsarealreadydigitalIftheTDMswitchdoesnotdigitizetheanalogsignalsthentherecanbeaproblemtheclocksusedtodigitizedonothaveidenticalfrequencieswegetbyteslips!

(well,actually,wecangetbitslipsfirst…)

exaggeratedpictorialexampleNumericalexample:clockderivedfrom8000Hz.quartzcrystaltypicalcrystalaccuracy=50ppmSo2crystalscandifferby100ppmi.e.0.8samples/secondSodifferenceis1sampleafter1?seconds

111111222222333333444444555666555777666888999777988componentsignalsTDMThefixWemustensurethatalltheclockshavethesamefrequencyEverytelephonynetworkhasanaccurateclockcalleda“stratum1”or“PrimaryReferenceClock”Allotherclocksaredirectlyorindirectlylockedtoit(master–slave)ATDMreceivingdevicecanlockontothesourceclockbasedontheincomingdata(FLL,PLL)Forthistowork,wemustensurethatthedatahasenoughtransitions(speciallinecoding,scramblingbits,etc.)10transitionsnotransitionsComparingclocksAclockissaidtobeisochronous

(isos=equal,chronos=time)ifitsticksareequallyspacedintime2clocksaresaidtobesynchronous

(syn=samechronos=time)iftheytickintime,i.e.havepreciselythesamefrequency2clocksaresaidtobeplesiochronous

(plesio=nearchronos=time)iftheyarenominallyifthesamefrequencybutarenotlockedPDHprincipleIfwewantyethigherrates,wecanmuxtogetherTDMsignals(tributaries)WecoulddemuxtheTDMtimeslotsanddirectlyremuxthembutthatistoocomplexTheTDMinputsarealreadydigital,sowemustinsistthatthemuxprovideclocktoalltributaries(notalwayspossible,mayalreadybelockedtoanetwork)ORsomehowtransporttributarywithitsownclockacrossahigherspeednetworkwithadifferentclock(withoutspoilingremoteclockrecovery)Atributaryisastreamorriverthatflowsintoamainstem(orparent)riveroralake.PDHhierarchies64kbps2.048Mbps1.544Mbps1.544Mbps6.312Mbps6.312Mbps8.448Mbps34.368Mbps139.264Mbps44.736Mbps32.064Mbps97.728Mbps274.176MbpsCEPTN.A.Japan43210levelx30x24x24*4*4*4*4*7*6*4*5*3E1E2E3E4T1T2T3T4J1J2J3J4TheEuropeanConferenceofPostalandTelecommunicationsAdministrationsFramingandoverheadInadditiontolockingontobit-rateweneedtorecognizetheframestructureWeidentifyframesbyaddingFrameAlignmentSignal

TheFASispartoftheframeoverhead(whichalsoincludes"C-bits",OAM,etc.)EachlayerinPDHhierarchyaddsitsownoverheadForexampleE1–2overheadbytesper32bytes–overhead6.25%E2–4E1s=8.192Mbpsoutof8.448Mbpssothereisanadditional0.256Mbps=3%altogether4*30*64kbps=7.680Mbpsoutof8.448Mbpsor9.09%overheadWhathappensnext?PDHoverheadOverheadalwaysincreaseswithdatarate!digitalsignaldatarate(Mbps)voicechannelsoverheadpercentageT11.544240.52%T26.312962.66%T344.7366723.86%T4274.17640325.88%E12.048306.25%E28.4481209.09%E334.36848010.61%E4139.264192011.76%OAManalogchannelsand64kbpsdigitalchannelsdonothavemechanismstochecksignalvalidityandqualitythusmajorfaultscouldgoundetectedforlongperiodsoftimehardtocharacterizeandlocalizefaultswhenreportedminordefectsmightbeunnoticedindefinitelySolutionistoaddmechanismsbasedonoverheadasPDHnetworksevolved,moreandmoreoverheadwasdedicatedtoOperations,AdministrationandMaintenance(OAM)functionsincluding:monitoringforvalidsignaldefectreportingalarmindication/inhibition(AIS)PDHJustificationInadditiontoFAS,PDHoverheadincludesjustificationcontrol(C-bits)andjustificationopportunity“stuffing”(R-bits)AssumethetributarybitrateisBTPositivejustificationpayloadisexpectedathighestbitrateB+TifthetributaryrateisactuallyatthemaximumbitratethenallpayloadandRbitsarefilledifthetributaryrateislowerthanthemaximumthensometimestherearenotenoughincomingbitssotheR-bitsarenotfilledandC-bitsindicatethisNegativejustificationpayloadisexpectedatlowestbitrateB-TifthetributaryrateisactuallytheminimumbitratethenpayloadspacesufficesifthetributaryrateishigherthantheminimumthensometimestherearenotenoughpositionstoaccommodatesoR-bitsintheoverheadareusedandtheC-bitsindicatethisPositive/NegativejustificationpayloadisexpectedatnominalbitrateBpositiveornegativejustificationisappliedasrequiredSONET/SDH

motivationandhistoryFirststepWiththedivestitureoftheUSBellsystemanewneedaroseMCIandNYNEXcouldn’tdirectlyinterconnectopticaltrunksInterexchangeCarrierCompatibilityForumrequestedT1tosolveproblemNeededmultivendor/multioperatorfiber-opticcommunicationsstandardThreemaintasks:Opticalinterfaces(wavelengths,powerlevels,etc)proposalsubmittedtoT1X1(Aug1984)T1.106standardonsinglemodeopticalinterfaces(1988)Operations(OAM)systemproposalsubmittedtoT1M1T1.119standardRates,formats,definitionofnetworkelementsBellcore(Yau-ChauChingandRodneyBoehm)proposal(Feb1985)proposedtoT1X1termSONETwascoinedT1.105standard(1988)PDHlimitationsRatelimitationsCopperinterfacesdefinedNeedtomux/demuxhierarchyoflevels(hardtopulloutasingletimeslot)OverheadpercentageincreaseswithrateAtleastthreedifferentsystems(Europe,NA,Japan)E2.048,8.448,34.348,139.264T1.544,3.152,6.312,44.736,91.053,274.176J1.544,3.152,6.312,32.064,97.728,397.2SoacompletelynewmechanismwasneededIdeabehindSONETSynchronousOpticalNETworkDesignedforopticaltransport(highbitrate)DirectmappingoflowerlevelsintohigheronesCarryallPDHtypesinone(!)universalhierarchyITUversion=SynchronousDigitalHierarchydifferentterminologybutinteroperableOverheaddoesn’tincreasewithrateOAMdesigned-infrombeginningStandardization!TheoriginalBellcoreproposal:hierarchyofsignals,allmultipleofbasicrate(50.688)basicrateabout50MbpstocarryDS3payloadbit-orientedmuxmechanismstocarryDS1,DS2,DS3Manyotherproposalsweremergedinto1987draftdocument(rate49.920)Insummerof1986CCITTexpressinterestincooperationneededarateofabout150MbpstocarryE4wantedbyteorientedmuxInitialcompromiseattemptbytemuxUSwanted13rows*180columnsCEPTwanted9rows*270columnsCompromise!USwouldusebasicrateof51.84Mbps,9rows*90columnsCEPTwouldusethreetimesthatrate-155.52Mbps,9rows*270columnsSONET/SDH

architectureLayersSONETwasdesignedwithdefinitelayeringconceptsPhysicallayer–opticalfiber(linearorring)whenexceedfiberreach–regeneratorsregeneratorsarenotmereamplifiers,regeneratorsusetheirownoverheadfiberbetweenregeneratorscalledsection

(regeneratorsection)Linelayer–linkbetweenSONETmuxes(Add/DropMultiplexers)inputandoutputatthislevelareVirtualTributaries(VCs)actually2layerslowerorderVC(forlowbitratepayloads)higherorderVC(forhighbitratepayloads)Pathlayer–end-to-endpathofclientdata(tributaries)clientdata(payload)maybePDHATMpacketdataSONETarchitectureSONET(SDH)hasat3layers:path–end-to-enddataconnection,muxestributarysignalspathsectionthereareSTSpaths+VirtualTributary(VT)pathsline–protectedmultiplexedSONETpayloadmultiplexsectionsection–physicallinkbetweenadjacentelementsregeneratorsectionEachlayerhasitsownoverheadtosupportneededfunctionalitySDHterminologyPathTerminationPathTerminationLineTerminationLineTerminationSectionTerminationpathlinelinelineADMADMregeneratorsectionsectionsectionsectionSTS,OC,etc.ASONETsignaliscalledaSynchronousTransportSignalThebasicSTSisSTS-1,allothersaremultiplesofit-STS-NThe(optical)physicallayersignalcorrespondingtoanSTS-NisanOC-NSONETOpticalrateSTS-1OC-151.84MSTS-3OC-3155.52MSTS-12OC-12622.080MSTS-48OC-482488.32MSTS-192OC-1929953.28M*3*4*4*4rates

and

framestructureSONET/SDHframesSynchronousTransferSignalsarebit-signals(OCareoptical)LikeallTDMsignals,thereareframingbitsatthebeginningoftheframeHowever,itisconvenienttodrawSONET/SDHsignalsasrectanglesframingSONETSTS-1frameEachSTS-1frameis90columns*9rows=810bytesThereare8000STS-1framespersecondsoeachbyterepresents64kbps(eachcolumnis576kbps)ThusthebasicSTS-1rateis51.840Mbps90columns9rowsframingSDHSTM-1frameSynchronousTransportModulesarethebit-signalsforSDHEachSTM-1frameis270columns*9rows=2430bytesThereare8000STM-1framespersecondThusthebasicSTM-1rateis155.520Mbps3timestheSTS-1rate!270columns9rows…SONET/SDHratesSTS-Nhas90NcolumnsSTM-McorrespondstoSTS-NwithN=3MSDHratesincreasebyfactorsof4eachtimeSTS/STMsignalscancarryPDHtributaries,forexample:STS-1cancarry1T3or28T1sor1E3or21E1sSTM-1cancarry3E3sor63E1sor3T3sor84T1sSONETSDHcolumnsrateSTS-19051.84MSTS-3STM-1270155.52MSTS-12STM-41080622.080MSTS-48STM-1643202488.32MSTS-192STM-64172809953.28MSONET/SDHtributariesE3andT3arecarriedasHigherOrderPaths(HOPs)E1andT1arecarriedasLowerOrderPaths(LOPs)(thenumbersarefordirectmapping)SONETSDHT1T3E1E3E4STS-1281211STS-3STM-18436331STS-12STM-433612252124STS-48STM-1613444810084816STS-192STMynchronousPayloadEnvelopeSTS-1framestructure9rowsTransportOverheadTOH6rows3rowsSectionoverhead

is3rows*3columns=9bytes=576kbpsframing,performancemonitoring,managementLineoverheadis6rows*3columns=18bytes=1152kbpsprotectionswitching,linemaintenance,mux/concat,SPEpointerSPEis9rows*87columns=783bytes=50.112MbpsSimilarly,STM-1has9(different)columnsofsection+lineoverhead!90columns9rowsSTM-1framestructureSectionOverheadSOHSTM-1has9(different)columnsoftransportoverhead!RSoverhead

is3rows*9columnsPointeroverheadis1row*9columnsMSoverheadis5rows*9columnsSPEis9rows*261columns…270columnsRSOHMSOHEvenhigherrates3STS-1scanformanSTS-34STM-1s(STS-3s)canformanSTM-4(STS-12)4STM-4s(STS-12s)canformanSTM-16(STS-48)etc.forSTM-N(STS-3N)Theprocedureisbyte-interleaving9rows9*Ncolumns270*NcolumnsByte-interleaving...ScramblingSONET/SDHreceiversrecoverclockbasedonincomingsignalInsufficientnumberof0-1transitionscausesdegradationofclockperformanceInordertoguaranteesufficienttransitions,SONET/SDHemployascramblerAlldataexceptfirstrowofsectionoverheadisscrambledScrambleris7bitself-synchronizingX7+X6+1ScramblerisinitializedwithonesAshortscramblerissufficientforvoicedatabutNOTfordatawhichmaycontainlongstretchesofzerosWhensendingdataanadditionalpayloadscramblerisusedmodernstandardsuse43bitX43+1runcontinuouslyonATMpayloadbytes(suspendedfor5bytesofcelltax)runcontinuouslyonHDLCpayloadsZ-43XnYn=

Xn+Yn-43STS-1OverheadTheSTS-1overheadconsistsof3rowsofsectionoverheadframesync(A1,A2)sectiontrace(J0)errorcontrol(B1)sectionorderwire(E1)EmbeddedOperationsChannel(Di)6rowsoflineoverheadpointerandpointeraction(Hi)errorcontrol(B2)AutomaticProtectionSwitchingsignaling(Ki)DataChannel(Di)SynchronizationStatusMessage(S1)FarEndBlockError(M0)lineorderwire(E2)A1A2J0B1E1F1D1D2D3H1H2H3B2K1K2D4D5D6D7D8D9D10D11D12S1M0E2sectionoverheadlineoverheadSTM-1OverheadA1A1A1A2A2A2J0resresB1mmE1mF1resresD1mmD2mD3B2B2B2K1K2D4D5D6D7D8D9D10D11D12S1M1E2RSOHMSOHSOHm–mediadependent(definedforSONETradio)res–reservedfornationaluseAUpointersA1,A2,J0(sectionoverhead)A1,A2-framingbytesA1=11110110A2=00101000SONET/SDHframingalwaysusesequalnumbersofA1andA2bytesJ0-regeneratorsectiontrace(inearlySONET-acountercalledC1)enablesreceivertobesurethatthesectionconnectionisstillOKenablesidentifyingindividualSTS/STMsaftermuxingJ0goesthrougha16bytesequenceMSBsareJ0framing(1000…00)CsareCRC-7ofpreviousframeSare157-bitcharacterssectionaccesspointidentifierSSSSSSS0SSSSSSS0C7C6C5C4C3C2C11…B1,E1,F1,D1-3(sectionoverhead)B1–ByteInterleavedParity-8byteevenparityofbitsofbytesofpreviousframeafterscramblingonly1BIT-8formultiplexedSTS/STME1–sectionorderwire64kbpsvoicelinkfortechniciansfromregeneratortoregeneratorF1–64kbpslinkforuserpurposesD1+D2+D3–192kbpsmessagingchannelusedbysectionterminationasEmbeddedOperationsChannel(SONET)orDataCommunicationsChannel(SDH)Pointers(lineoverhead)InSONET,pointersareconsideredpartoflineoverheadForSTS-1,H1+H2isthepointer,H3isthepointeractionH1+H2indicatestheoffset(inbytes)fromH3totheSPE(i.e.if0thenJ1POHbyteisimmediatelyafterH3intherow)4MSBsareNewDataFlag,10LSBsareactualoffsetvalue(0–782)Whenoffset=522theSTS-1SPEisinasingleSTS-1frameInallothercasestheSPEstraddlestwoframesWhenoffsetisamultipleof87,theSPEisrectangular

TocompensateforclockdifferenceswehavepointerjustificationWhennegativejustificationH3carriestheextradataWhenpositivejustificationbyteafterH3isstuffingbyteSONETJustificationIftributaryrateisabovenominal,negativejustificationisneededWhenlessthan8morebitsthanexpectedinbufferNDFis0110offsetunchangedWhen8extrabitsaccumulateNDFissetto1001extrabyteplacedintoH3offsetisdecrementedby1(byte)Iftributaryrateisbelownominal,positivejustificationisneededWhenlessthan8fewerthanexpectedbitsinbufferNDFis0110offsetunchangedWhen8missingbitsNDFissetto1001byteafterH3isstuffingoffsetisincrementedby1(byte)H1H2extra…H1H2H3stuff…B2,K1,K2,D4-D12(lineoverhead)B2–BIP-8oflineoverhead+previousenvelope

(w/oscrambling)NB2sformuxedSTM-NK1andK2areusedforAutomaticProtectionSwitching

(seelater)D4–D12area576KbpsDataCommunicationsChannelbetweenmultiplexersusuallymanufacturerspecificOAMfunctionsS1,M0,E2(lineoverhead)S1–SynchronizationStatusMessageindicatesstratumlevel(unknown,stratum1,…,donotuse)M0–FarEndBlockErrorindicatesnumberofBIPviolationsdetectedE2–lineorderwire64kbpsvoicelinkfortechniciansfromlinemuxtolinemuxPayloads

and

MappingsSTS-1HOPSPEstructureWesawthatthepointerthelineoverheadpointstotheSTSpathoverheadPOH(afterre-arranging)POHisonecolumnof9rows(9bytes=576kbps)STS-1HOP1columnofSPEisPOH2more(“fixedstuffing”)columnsarereservedWeareleftwith84columns=756bytes=48.384MbpsforpayloadThisisenoughforaE3(34.368M)oraT3(44.736M)1875930STS-1Pathoverhead1columnofoverheadforpath(576Kbps)POHisresponsibleforpathtypeidentificationpathperformancemonitoringstatus

(includingofmappedpayloads)virtualconcatenationpathprotectiontraceJ1B3C2G1F2H4F3K3N1POHJ1,B3,C2(pathoverhead)J1–pathtraceenablesreceivertobesurethatthepathconnectionisstillOKB3–BIP-8evenbitparityofbytes(withoutscrambling)ofpreviouspayloadC2–pathsignallabelidentifiesthepayloadtype(examplesintable)C2(hex)Payloadtype00unequipped01nonspecific02LOP(TUG)04E3/T312E413ATM16PoS–RFC166218LAPSX.851A10GEthernet1BGFPCFPoS-RFC1619G1,F2,H4,F3,K3,N1(pathoverhead)G1–pathstatusconveysstatusandperformancebacktooriginator4MSBsarepathFEBE,1bitRDI,3unusedF2andF3–userspecificcommunicationsH4–usedforLOPmultiframesyncandVCAT(seelater)K3(4MSBs)–pathAPSN1–TandemConnectionMonitoringMessagingchannelfortandemconnectionsLOPTocarrylowerratepayloads,dividethe84availablecolumnsinto7*12interleavedcolumns,i.e.7VirtualTributary(VT)GroupsVTgroupis12columnsof9rows,i.e.108bytesor6.912MbpsVTgroupiscomposedofVT(s)therearedifferenttypesofVTinordertocarrydifferenttypesofpayloadallVTsinVTgroupmustbeofthesametype(nomixing)butdifferentVTgroupsinsameSPEcanhavedifferentVTtypesAVTcanhave3,4,6or12columns187593012345677VTGsSONET/SDH:VT/VCtypesVT/STSVCcolumnratepayloadVT1.5VC-1131.728DS1(1.544)VT2VC-1242.304E1(2.048)VT363.456DS1C(3.152)VT6VC-2126.912DS2(6.312)STS-1VC-348.384E3(34.368)STS-1VC-348.384DS3(44.736)STS-3cVC-4149.760E4(139.264)LOPHOPstandardPDHratesmapefficientlyintoSONET/SDH!4pergroup3pergroup2pergroup1pergroupLOPathoverheadLOPOHisresponsiblefortiming,PM,REI,…LOPathAPSsignalingis4MSBsofbyteK4V5J2N2K4V1pointerV2pointerV3pointerV4pointerVC11–25BVC12–34B125msec500msecH4=XXXXXX00H4=XXXXXX01H4=XXXXXX10H4=XXXXXX11VC11–27BVC12–36BPayloadcapacityVT1.5/VC-11has3columns=27bytes=1.728Mbpsbut2bytesareusedforoverhead(V1/V2/V3/V4andV5/J2/N2/K4)soactuallyonly25bytes=1.6MbpsareavailableSimilarlyVT2/VC-12has4columns=36bytes=2.304Mbpsbut2bytesareusedforoverheadSoactuallyonly34bytes=2.176MbpsareavailableLOPoverheadV5consistsofBIP(2b)REI(1b)RFI(1b)Signallabel(3b)(uneq,async,bit-sync,byte-sync,test,AIS)RDI(1b)J2ispathtraceN2isthenetworkoperatorbytemaybeusedforLOPtandemconnectionmonitoring(LO-TCM)K4isforLOVCATandLOAPSSDHContainersTributarypayloadsarenotplaceddirectlyintoSDHPayloadsareplaced(adapted)intocontainersThecontainersaremadeintovirtualcontainers(byaddingPOH)Next,thepointerisused–thepointer+VCisaTUorAUTributaryUnitadaptsalowerorderVCtohighorderVCAdministrativeUnitadaptshigherorderVCtoSDHTUsandAUsaregroupedtogetheruntiltheyarebigenoughWefinallygetanAdministrativeUnitGroupTotheAUGweaddSOHtomaketheSTMframeFormally…C-nn=11,12,2,3,4VC-n=POH+C-nTU-n=pointer+VC-n(n=11,12,2,3)AU-n=pointer+VC-n(n=3,4)TUG=N*TU-nAUG=N*AU-nSTM-N=SOH+AUGMultiplexingAnAUGmaycontainaVC-4withanE4oritmaycontain3AU-3seachwithaVC-3swithanE3Inthelattercase,theAUpointerpointstotheAUGandinsidetheAUGare3pointerstotheAU-3sJ1B3C2G1F2H4F3K3N1H1H1H1H2H2H2H3H3H3MoremultiplexingSimilarly,wecanhierarchicallybuildcomplexstructuresLowerrateSTMscanbecombinedintohigherrateSTMsAUGscanbecombinedintoSTMsAUscanbecombinedintoAUGsTUGscanbecombinedintohighorderVCsLowerrateTUscanbecombinedintoTUGsetc.ButonlycertaincombinationsareallowedbystandardsAllSDHmappingsSTM-NAU-3VC-3C3VC-3TU-3TUG-3C-4VC-4AU-4AUG…AUGAUGC2C12C11TUG-2VC-2TU-2VC-12TU-12VC-11TU-11STM-0ATM2.144ME4139.264MATM1.6MATM149.760MATM48.384MATM6.874ME334.368MT344.736MT26.312ME12.048MT11.544M*3*7*3*7*4*3AllSONETmappingsSTS-NSTS-3SPESTS-3cSTS-1VT6SPEVT2SPEVT1.5SPEVT6VT-2VT1.5ATM2.144ME4139.264MATM1.6MATM149.760MATM48.384MATM6.874ME334.368MT344.736MT26.312ME12.048MT11.544M*NSTS-1SPEVTG*7pointerprocessing*3*4TributarymappingtypesWhenmappingtributariesintoVCs,PDH-likebit-stuffingisusedForE1andT1thereareseveraloptionsAsynchronousmapping(framing-agnostic)BitsynchronousmappingBytesynchronousmapping(time-slotaligned)E4intoVC-4,E3/T3intoVC-3arealwaysasynchronousT1intoVC-11maybeanyofthe3(inbytesynchronoustheframingbitisplacedintheVCoverhead)E1intoVC-12maybeasynchronousorbytesynchronousWAN-PHY(10GbEinSTM-64)Thereisaspecialcasewherethebit-ratesworkoutrelativelywellGbE10GBASE-R(64B/66Bcoding)canbedirectlymappedintoaSTM-64(withcontiguousconcatenation-seelater)withoutneedforGFPMACcreates"stretchedInterPacketGap"tocompensateforratebeing<10GThisisthefastestconnectioncommonlyusedforInternettrafficComplication:SDHclockaccuracyis4.6ppm,GbEaccuracyis20ppm64*(270-9)=16704columnsJ163columnsoffixedstuff10GBASE-W802.3-2005Clause50Protection

and

RingsWhatisprotection?SONET/SDHneedtobehighlyreliable(fivenines)Down-timeshouldbeminimal(lessthan50msec)Sosystemsmustrepairthemselves(notimeformanualintervention)Upondetectionofafailure(dLOS,dLOF,highBER)thenetworkmustreroutetraffic(protectionswitching)fromworkingchanneltoprotectionchannelTheNetworkElementthatdetectsthefailure(tail-endNE)initiatestheprotectionswitchingThehead-endNEmustchangeforwardingortosendduplicatetrafficProtectionswitchingisunidirectionalProtectionswitchingmayberevertive(automaticallyreverttoworkingchannel)head-endNEtail-endNEworkingchannelprotectionchannelHowdoesitwork?Head-endandtail-endNEshavebridges(muxes)Head-endandtail-endNEsmaintainbidirectionalsignalingchannelSignalingiscontainedinK1andK2bytesofprotectionchannelK1–tail-endstatusandrequestsK2–head-endstatushead-endbridgetail-endbridgeworkingchannelprotectionchannelsignalingchannelLinear1+1protectionSimplestformofprotectionCanbeatOC-nlevel(differentphysicalfibers)oratSTM/VClevel(calledSubNetworkConnectionProtection)orend-to-endpath(calledtrailprotection)Head-endbridgealwayssendsdataonbothchannelsTail-endchooseschanneltousebasedonBER,dLOS,etc.NoneedforsignalingIfnon-revertivethereisnodistinctionbetweenworkingandprotectionchannelsBWutilizationis50%channelAchannelBLinear1:1protectionHead-endbridgeusuallysendsdataonworkingchannelWhentail-enddetectsfailureitsignals(usingK1)tohead-endHead-endthenstartssendingdataoverprotectionchannelWhennotinuseprotectionchannelcanbeusedfor(discounted)extratraffic

(pre-emptibleunprotectedtraffic)Maybeatanylayer(onlyOC-nlevelprotectsagainstfibercuts)workingcha