文档介绍：RingProtectionOverview March,2008 ITU-TQ9–--TSG15/,-,Principles,(andamendedQbridges),,forwarding,flushbehaviourandportblocking/(eitherapre-determinedlinkorafailedlink).MonitoringoftheETHlayerfordiscoveryandidentificationofSignalFailure(SF)(RPL)–LinkdesignatedbymechanismthatisblockedduringIdlestatetopreventlooponBridgedringRPLOwner–NodeconnectedtoRPLthatblockstrafficonRPLduringIdlestateandunblocksduringProtectedstateLinkMonitoring–OAMmessages(CFM)SignalFail(SF)–HtrailsignalfailconditionisdetectedNoRequest(NR)–NoRequestisdeclaredwhentherearenooutstandingconditions(.,SF,etc.)onthenodeRingAPS(R-APS)Messages–(APS)Channel-Ring-wideVLANusedexclusivelyfortransmissionofOAMmessagesincludingR-(WaittoRestore)Timer–UsedbytheRPLOwnertoverifythattheringhasstabilizedbeforeblockingtheRPLafterSFRecov