ITUTG8032ERPS协议介绍

G.8032EthernetRingProtectionOverviewMarch,2008ITU-TQ9SG15,2,Agenda,G.8032RecommendationIntroductionG.8032ObjectivesandPrinciplesG.8032ConceptsG.8032ProtectionSwitchingG.8032R-APSMessagesG.8032ItemsUnderStudy,3,ITU-TSG15/Q9G.8032Recommendation,G.8032RecommendationconsentedFebruary2008ThisRecommendationdefinestheAPSprotocolandprotectionswitchingmechanismsforETHlayerringtopologies.Includedaredetailspertainingtobridgedringprotectioncharacteristics,architecturesandtheringAPSprotocol.,G.8032ProposalsandContributions,G.8032ConvergedProposals,G.8032ERPWorkItemApprovedinITU-T,G.8032Objective,Principles,andRequirementsSetting,G.8032RecommendationConsent,4,G.8032ObjectivesandPrinciples,Useofstandard802MACandOAMframesaroundthering.Usesstandard802.1Q(andamendedQbridges),butwithxSTPdisabled.RingnodessupportsstandardFDBMAClearning,forwarding,flushbehaviourandportblocking/unblockingmechanisms.Preventsloopswithintheringbyblockingoneofthelinks(eitherapre-determinedlinkorafailedlink).MonitoringoftheETHlayerfordiscoveryandidentificationofSignalFailure(SF)conditions.Protectionandrecoveryswitchingwithin50msfortypicalrings.Totalcommunicationfortheprotectionmechanismshouldconsumeaverysmallpercentageoftotalavailablebandwidth.,5,G.8032TermsandConcepts,RingProtectionLink(RPL)LinkdesignatedbymechanismthatisblockedduringIdlestatetopreventlooponBridgedringRPLOwnerNodeconnectedtoRPLthatblockstrafficonRPLduringIdlestateandunblocksduringProtectedstateLinkMonitoringLinksofringaremonitoredusingstandardETHCCOAMmessages(CFM)SignalFail(SF)SignalFailisdeclaredwhenETHtrailsignalfailconditionisdetectedNoRequest(NR)NoRequestisdeclaredwhentherearenooutstandingconditions(e.g.,SF,etc.)onthenodeRingAPS(R-APS)MessagesProtocolmessagesdefinedinY.1731andG.8032AutomaticProtectionSwitching(APS)Channel-Ring-wideVLANusedexclusivelyfortransmissionofOAMmessagesincludingR-APSmessages,6,G.8032Timers,G.8032specifiestheuseofdifferenttimerstoavoidraceconditionsandunnecessaryswitchingoperationsWTR(WaittoRestore)TimerUsedbytheRPLOwnertoverifythattheringhasstabilizedbeforeblockingtheRPLafterSFRecoveryHold-offTimersUsedbyunderlyingETHlayertofilteroutintermittentlinkfaultsFaultswillonlybereportedtotheringprotectionmechanismifthistimerexpires,7,ControllingtheProtectionMechanism,ProtectionswitchingtriggeredbyDetection/clearingofSignalFailure(SF)byETHCCOAMRemoterequestsoverR-APSchannel(Y.1731)ExpirationofG.8032timersR-APSrequestscontrolthecommunicationandstatesoftheringnodesTwobasicR-APSmessagesspecified-R-APS(SF)andR-APS(NR)RPLOwnermaymodifytheR-APS(NR)indicatingtheRPLisblocked:R-APS(NR,RB)RingnodesmaybeinoneoftwostatesIdlenormaloperation,nolink/nodefaultsdetectedinringProtectingProtectionswitchingineffectafteridentifyingasignalfault,8,PhysicaltopologyhasallnodesconnectedinaringERPguaranteeslackofloopbyblockingtheRPL(linkbetween6&1infigure)Logicaltopologyhasallnodesconnectedwithoutaloop.EachlinkismonitoredbyitstwoadjacentnodesusingETHCCOAMmessagesSignalFailureasdefinedinY.1731,istriggertoringprotectionLossofContinuityServerlayerfailure(e.g.PhyLinkDown),RPLOwner,RPL,ETH-CC,ETH-CC,ETH-CC,ETH-CC,ETH-CC,ETH-CC,Physicaltopology,Logicaltopology,RingIdleState,9,ProtectionSwitchingLinkFailure,Link/nodefailureisdetectedbythenodesadjacenttothefailure.Thenodesadjacenttothefailure,blockthefailedlinkandreportthisfailuretotheringusingR-APS(SF)messageR-APS(SF)messagetriggersRPLOwnerunblockstheRPLAllnodesperformFDBflushingRingisinprotectionstateAllnodesremainconnectedinthelogicaltopology.,Physicaltopology,Logicaltopology,RPLOwner,RPL,10,ProtectionSwitchingFailureRecovery,Whenthefailedlinkrecovers,thetrafficiskeptblockedonthenodesadjacenttotherecoveredlinkThenodesadjacenttotherecoveredlinktransmitR-APS(NR)messageindicatingtheyhavenolocalrequestpresentWhentheRPLOwnerreceivesR-APS(NR)messageitStartsWTRtimerOnceWTRtimerexpires,RPLOwnerblocksRPLandtransmitsR-APS(NR,RB)messageNodesreceivingthemessageperformaFDBFlushandunblocktheirpreviouslyblockedportsRingisnowreturnedtoIdlestate,RPLOwner,RPL,Physicaltopology,Logicaltopology,1,2,6,4,3,5,11,SignalingChannelInformation,ERPusesR-APSmessagestomanageandcoordinatetheprotectionswitchingR-APSdefinedinY.1731-OAMcommonfieldsaredefinedinY.1731.Version00000forthisversionofRecommendationOpCodedefinedtobe40inY.1731Flags00000000shouldbeignoredbyERP,12,R-APSSpecificInformation,Specificinformation(32octets)definedbyG.8032Request/Status(4bits)1011=SF|0000=NR|Other=FutureStatusRB(1bit)SetwhenRPLisblocked(usedbyRPLOwnerinNR)StatusDNF(1bit)SetwhenFDBFlushisnotnecessary(Future)NodeID(6octets)MACaddressofmessagesourcenode(Informational)Reserved1(4bits),StatusReserved(6bits),Reserved2(24octets)-Futuredevelopment,13,ItemsUnderStudy,G.8032iscurrentlyaninitialrecommendationthatwillcontinuetobeenhanced.Thefollowingtopicsareunderstudyforfutureversionsoftherecommendation:Interconnectedringsscenarios:sharednode,sharedlinksRPLblockedatbothendsconfigurationoftheringwherebothnodesconnectedtotheRPLcontroltheprotectionmechanismSupportforManualSwitchadministrativedecisiontoclosedownalinkandforcea“recovery”situationarenecessaryfornetworkmaintenanceSupportforSignalDegradescenariosSDsituationsneedspecialconsiderationforanyprotectionmechanismNon-revertivemodeAllowsthenetworktoremainin“recovery”configurationeitheruntilanewsignalfailureoradministrativeswitchingRPLDisplacementDisplacementoftheroleoftheRPLtoanotherringlinkflexiblyinthenormal(idle)conditionIn-depthanalysisofdifferentoptimizations(e.g.,FDBflushing)Etc.,14,ThankYou,15,Backup,16,G.8032BasicFunctions,17,ERPFunctionalityDecomposition,InputsLocalnoderequests,ETHsignals,R-APSmessages,WTRTimer.FiltersLocalPriorityLogic,ValidityCheck,GuardTimer,PriorityLogicguaranteethathighestprioritymessagearrivesforprocessing.,ERPProcessingR-APSRequestProcessingprocessesfilteredmessageaccordingtoStateMachinewithknowledgeofcurrentstateandRPL-OwnerindicationOutputsNodefunctions(FDBFlushing,Block/Unblockport),sending(orstopping)R-APSmessages,18,StateMachine,ThreenodestatesInitializationwhenfirstdefiningtheringA(Idle)thenormalstateoftheringnodeswithRPLblockedandallnodes/portsworkingB(Protecting)whenprotectionswitchingisineffect,RPLunblocked,other(usuallyfault)linkisblocked.DifferentinputmessagesassignedpriorityasappearsintheStateMachinedescription.PrioritymechanismtoallowproperreactiontofaultsStateMachinedescribestheactionstobetakenbythenodedependentoncurrentstateandinputmessage.Onlymessagewithhighestprioritywillpassthroughthefiltering.DifferentactionsincludetransmissionofR-APSmessage,blocking/unblockingaport,flushingtheFDB,switchingcurrentstateofnode,andstarting/stoppingtimers.,19,StateMachine,FDBflushingwillclearallofthelearnedfilteringruleswithinthenode.CurrentRecommendationincludesbasicoptimizationonlyflushingonceonfaultdiscoveryandonceonrecovery.DNFstatusflagisforfuturedefinition,20,SwitchingTriggers,Detection/ClearingofSF(SignalFail):SF:LossofCCM,SFsignalpassedupfromunderlying(sub)layerSwitchingisperformedwhenhold-offtimerexpiresafterdetectionofSF.Operatorsrequest:Lockout,Forcedswitch,Manualswitch,Clear(forfuturespecification)Remoterequest:SwitchingrequestindicatedinreceivedR-APSinformationfromtheothernode.Protectionswitchingalgorithmisbasedonprioritiesassignedtoalltriggers,21,EthernetRingsandtheRPL,Ethernetnodesconnectedinaringtopology.Eachnodeconnectedtotwoneighborsvialinks(E&Wports)Deterministicnetworktopology,Avoidloopswithinringbyblockingadesignatedlink(RPL)NoderesponsibletocontroltheblockingstateofRPLisRPLownerRPLisunblockedduringprotectionstateandmayreverttoblockedduringrecovery,RPL,22,RPLOwnerreceivesSFmessageandunblocksitsendofRPLlinkrow3StableStateSFmessagesontheringFurtherSFmessagestriggernofurtheractionrow10,B,C,D,E,F,G,A,SF,Normal,Protectionstate,failure,SF,SF,A,ScenarioA-NormaltoProtection,NormalStateFailureOccursNodesCandDdetectlocalSignalFailureconditionandafterrespectinghold-offtimeandBlockfailedportrow1NodeCandDperiodicallysendSFmessage,onbothringports,whileSFconditionpersists.EachnodeperformsaFDBFlushwhenreceivingtheSFmessage,RPLOwner,B,SF,SF,C,D,E,SF,SF,SF,SF,SF,SF,F,50ms,G,RPL,Flush,Flush,Flush,Flush,Flush,Flush,Flush,23,WhennodeCandDexpirethegu