ITUTG8032 ERPS协议介绍

G.8032EthernetRingProtectionOverviewMarch,2008ITU-TQ9–SG152AgendaG.8032RecommendationIntroductionG.8032ObjectivesandPrinciplesG.8032ConceptsG.8032ProtectionSwitchingG.8032R-APSMessagesG.8032ItemsUnderStudy3ITU-TSG15/Q9G.8032RecommendationG.8032RecommendationconsentedFebruary2008ThisRecommendationdefinestheAPSprotocolandprotectionswitchingmechanismsforETHlayerringtopologies.Includedaredetailspertainingtobridgedringprotectioncharacteristics,architecturesandtheringAPSprotocol.JANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECJANFEBMAR200620072008G.8032ProposalsandContributionsG.8032ConvergedProposalsG.8032ERPWorkItemApprovedinITU-TG.8032Objective,Principles,andRequirementsSettingG.8032RecommendationConsent4G.8032ObjectivesandPrinciplesUseofstandard802MACandOAMframesaroundthering.Usesstandard802.1Q(andamendedQbridges),butwithxSTPdisabled.RingnodessupportsstandardFDBMAClearning,forwarding,flushbehaviourandportblocking/unblockingmechanisms.Preventsloopswithintheringbyblockingoneofthelinks(eitherapre-determinedlinkorafailedlink).MonitoringoftheETHlayerfordiscoveryandidentificationofSignalFailure(SF)conditions.Protectionandrecoveryswitchingwithin50msfortypicalrings.Totalcommunicationfortheprotectionmechanismshouldconsumeaverysmallpercentageoftotalavailablebandwidth.5G.8032TermsandConceptsRingProtectionLink(RPL)–LinkdesignatedbymechanismthatisblockedduringIdlestatetopreventlooponBridgedringRPLOwner–NodeconnectedtoRPLthatblockstrafficonRPLduringIdlestateandunblocksduringProtectedstateLinkMonitoring–LinksofringaremonitoredusingstandardETHCCOAMmessages(CFM)SignalFail(SF)–SignalFailisdeclaredwhenETHtrailsignalfailconditionisdetectedNoRequest(NR)–NoRequestisdeclaredwhentherearenooutstandingconditions(e.g.,SF,etc.)onthenodeRingAPS(R-APS)Messages–ProtocolmessagesdefinedinY.1731andG.8032AutomaticProtectionSwitching(APS)Channel-Ring-wideVLANusedexclusivelyfortransmissionofOAMmessagesincludingR-APSmessages6G.8032TimersG.8032specifiestheuseofdifferenttimerstoavoidraceconditionsandunnecessaryswitchingoperationsWTR(WaittoRestore)Timer–UsedbytheRPLOwnertoverifythattheringhasstabilizedbeforeblockingtheRPLafterSFRecoveryHold-offTimers–UsedbyunderlyingETHlayertofilteroutintermittentlinkfaultsFaultswillonlybereportedtotheringprotectionmechanismifthistimerexpires7ControllingtheProtectionMechanismProtectionswitchingtriggeredbyDetection/clearingofSignalFailure(SF)byETHCCOAMRemoterequestsoverR-APSchannel(Y.1731)ExpirationofG.8032timersR-APSrequestscontrolthecommunicationandstatesoftheringnodesTwobasicR-APSmessagesspecified-R-APS(SF)andR-APS(NR)RPLOwnermaymodifytheR-APS(NR)indicatingtheRPLisblocked:R-APS(NR,RB)RingnodesmaybeinoneoftwostatesIdle–normaloperation,nolink/nodefaultsdetectedinringProtecting–Protectionswitchingineffectafteridentifyingasignalfault8A.PhysicaltopologyhasallnodesconnectedinaringB.ERPguaranteeslackofloopbyblockingtheRPL(linkbetween6&1infigure)C.Logicaltopologyhasallnodesconnectedwithoutaloop.D.EachlinkismonitoredbyitstwoadjacentnodesusingETHCCOAMmessagesE.SignalFailureasdefinedinY.1731,istriggertoringprotectionLossofContinuityServerlayerfailure(e.g.PhyLinkDown)RPLOwnerRPLETH-CCETH-CCETH-CCETH-CCETH-CCETH-CCETH-CCETH-CCETH-CCETH-CCETH-CCETH-CCPhysicaltopologyLogicaltopology126435RPL126435RingIdleState9ProtectionSwitchingLinkFailureA.Link/nodefailureisdetectedbythenodesadjacenttothefailure.B.Thenodesadjacenttothefailure,blockthefailedlinkandreportthisfailuretotheringusingR-APS(SF)messageC.R-APS(SF)messagetriggersRPLOwnerunblockstheRPLAllnodesperformFDBflushingD.RingisinprotectionstateE.Allnodesremainconnectedinthelogicaltopology.PhysicaltopologyLogicaltopology126435RPL126435RPL126435126435RPLOwnerRPLR-APS(SF)R-APS(SF)R-APS(SF)R-APS(SF)10ProtectionSwitchingFailureRecoveryA.Whenthefailedlinkrecovers,thetrafficiskeptblockedonthenodesadjacenttotherecoveredlinkB.ThenodesadjacenttotherecoveredlinktransmitR-APS(NR)messageindicatingtheyhavenolocalrequestpresentC.WhentheRPLOwnerreceivesR-APS(NR)messageitStartsWTRtimerD.OnceWTRtimerexpires,RPLOwnerblocksRPLandtransmitsR-APS(NR,RB)messageE.Nodesreceivingthemessage–performaFDBFlushandunblocktheirpreviouslyblockedportsF.RingisnowreturnedtoIdlestateRPLOwnerRPLR-APS(NR)R-APS(NR)R-APS(NR)R-APS(NR)R-APS(NR,RB)R-APS(NR,RB)PhysicaltopologyLogicaltopology126435RPL126435126435RPL12643511SignalingChannelInformationERPusesR-APSmessagestomanageandcoordinatetheprotectionswitchingR-APSdefinedinY.1731-OAMcommonfieldsaredefinedinY.1731.Version–‘00000’–forthisversionofRecommendationOpCode–definedtobe40inY.1731Flags–‘00000000’–shouldbeignoredbyERP1234876543218765432187654321876543211MELVersion(0)OpCode(R-APS=40)Flags(0)TLVOffset(32)5R-APSSpecificInformation(32octets)..…37[optionalTLVstartshere;otherwiseEndTLV]lastEndTLV(0)DefinedbyY.1731DefinedbyG.8032Non-specifiedcontent12R-APSSpecificInformationSpecificinformation(32octets)definedbyG.8032Request/Status(4bits)–‘1011’=SF|’0000’=NR|Other=FutureStatus–RB(1bit)–SetwhenRPLisblocked(usedbyRPLOwner