《ITUTG8032ERPS协议介绍.ppt》由会员分享，可在线阅读，更多相关《ITUTG8032ERPS协议介绍.ppt（23页珍藏版）》请在三一办公上搜索。
1、G.8032Ethernet Ring Protection OverviewMarch,2008ITU-T Q9 SG 15,2,Agenda,G.8032 Recommendation IntroductionG.8032 Objectives and PrinciplesG.8032 ConceptsG.8032 Protection SwitchingG.8032 R-APS MessagesG.8032 Items Under Study,3,ITU-T SG15/Q9 G.8032 Recommendation,G.8032 Recommendation consented Feb
2、ruary 2008This Recommendation defines the APS protocol and protection switching mechanisms for ETH layer ring topologies.Included are details pertaining to bridged ring protection characteristics,architectures and the ring APS protocol.,G.8032 Proposals and Contributions,G.8032 Converged Proposals,G
3、.8032 ERP Work Item Approved in ITU-T,G.8032 Objective,Principles,and Requirements Setting,G.8032 Recommendation Consent,4,G.8032 Objectives and Principles,Use of standard 802 MAC and OAM frames around the ring.Uses standard 802.1Q(and amended Q bridges),but with xSTP disabled.Ring nodes supports st
4、andard FDB MAC learning,forwarding,flush behaviour and port blocking/unblocking mechanisms.Prevents loops within the ring by blocking one of the links(either a pre-determined link or a failed link).Monitoring of the ETH layer for discovery and identification of Signal Failure(SF)conditions.Protectio
5、n and recovery switching within 50 ms for typical rings.Total communication for the protection mechanism should consume a very small percentage of total available bandwidth.,5,G.8032 Terms and Concepts,Ring Protection Link(RPL)Link designated by mechanism that is blocked during Idle state to prevent
6、 loop on Bridged ringRPL Owner Node connected to RPL that blocks traffic on RPL during Idle state and unblocks during Protected stateLink Monitoring Links of ring are monitored using standard ETH CC OAM messages(CFM)Signal Fail(SF)Signal Fail is declared when ETH trail signal fail condition is detec
7、tedNo Request(NR)No Request is declared when there are no outstanding conditions(e.g.,SF,etc.)on the nodeRing APS(R-APS)Messages Protocol messages defined in Y.1731 and G.8032Automatic Protection Switching(APS)Channel-Ring-wide VLAN used exclusively for transmission of OAM messages including R-APS m
8、essages,6,G.8032 Timers,G.8032 specifies the use of different timers to avoid race conditions and unnecessary switching operationsWTR(Wait to Restore)Timer Used by the RPL Owner to verify that the ring has stabilized before blocking the RPL after SF RecoveryHold-off Timers Used by underlying ETH lay
9、er to filter out intermittent link faultsFaults will only be reported to the ring protection mechanism if this timer expires,7,Controlling the Protection Mechanism,Protection switching triggered by Detection/clearing of Signal Failure(SF)by ETH CC OAMRemote requests over R-APS channel(Y.1731)Expirat
10、ion of G.8032 timersR-APS requests control the communication and states of the ring nodesTwo basic R-APS messages specified-R-APS(SF)and R-APS(NR)RPL Owner may modify the R-APS(NR)indicating the RPL is blocked:R-APS(NR,RB)Ring nodes may be in one of two statesIdle normal operation,no link/node fault
11、s detected in ringProtecting Protection switching in effect after identifying a signal fault,8,Physical topology has all nodes connected in a ringERP guarantees lack of loop by blocking the RPL(link between 6&1 in figure)Logical topology has all nodes connected without a loop.Each link is monitored
12、by its two adjacent nodes using ETH CC OAM messagesSignal Failure as defined in Y.1731,is trigger to ring protectionLoss of ContinuityServer layer failure(e.g.Phy Link Down),RPL Owner,RPL,ETH-CC,ETH-CC,ETH-CC,ETH-CC,ETH-CC,ETH-CC,Physical topology,Logical topology,Ring Idle State,9,Protection Switch
13、ing Link Failure,Link/node failure is detected by the nodes adjacent to the failure.The nodes adjacent to the failure,block the failed link and report this failure to the ring using R-APS(SF)messageR-APS(SF)message triggersRPL Owner unblocks the RPLAll nodes perform FDB flushingRing is in protection
14、 stateAll nodes remain connected in the logical topology.,Physical topology,Logical topology,RPL Owner,RPL,10,Protection Switching Failure Recovery,When the failed link recovers,the traffic is kept blocked on the nodes adjacent to the recovered linkThe nodes adjacent to the recovered link transmit R
15、-APS(NR)message indicating they have no local request present When the RPL Owner receives R-APS(NR)message it Starts WTR timerOnce WTR timer expires,RPL Owner blocks RPL and transmits R-APS(NR,RB)messageNodes receiving the message perform a FDB Flush and unblock their previously blocked portsRing is
16、 now returned to Idle state,RPL Owner,RPL,Physical topology,Logical topology,1,2,6,4,3,5,11,Signaling Channel Information,ERP uses R-APS messages to manage and coordinate the protection switchingR-APS defined in Y.1731-OAM common fields are defined in Y.1731.Version 00000 for this version of Recomme
17、ndationOpCode defined to be 40 in Y.1731Flags 00000000 should be ignored by ERP,12,R-APS Specific Information,Specific information(32octets)defined by G.8032Request/Status(4bits)1011=SF|0000=NR|Other=FutureStatus RB(1bit)Set when RPL is blocked(used by RPL Owner in NR)Status DNF(1bit)Set when FDB Fl
18、ush is not necessary(Future)NodeID(6octets)MAC address of message source node(Informational)Reserved1(4bits),Status Reserved(6bits),Reserved2(24octets)-Future development,13,Items Under Study,G.8032 is currently an initial recommendation that will continue to be enhanced.The following topics are und
19、er study for future versions of the recommendation:Interconnected rings scenarios:shared node,shared linksRPL blocked at both ends configuration of the ring where both nodes connected to the RPL control the protection mechanismSupport for Manual Switch administrative decision to close down a link an
20、d force a“recovery”situation are necessary for network maintenanceSupport for Signal Degrade scenarios SD situations need special consideration for any protection mechanismNon-revertive mode Allows the network to remain in“recovery”configuration either until a new signal failure or administrative sw
21、itchingRPL Displacement Displacement of the role of the RPL to another ring link flexibly in the normal(idle)condition In-depth analysis of different optimizations(e.g.,FDB flushing)Etc.,14,Thank You,15,Backup,16,G.8032 Basic Functions,17,ERP Functionality Decomposition,Inputs Local node requests,ET
22、H signals,R-APS messages,WTR Timer.Filters Local Priority Logic,Validity Check,Guard Timer,Priority Logic guarantee that highest priority message arrives for processing.,ERP Processing R-APS Request Processing processes filtered message according to State Machine with knowledge of current state and
23、RPL-Owner indicationOutputs Node functions(FDB Flushing,Block/Unblock port),sending(or stopping)R-APS messages,18,State Machine,Three node states Initialization when first defining the ringA(Idle)the normal state of the ring nodes with RPL blocked and all nodes/ports workingB(Protecting)when protect
24、ion switching is in effect,RPL unblocked,other(usually fault)link is blocked.Different input messages assigned priority as appears in the State Machine description.Priority mechanism to allow proper reaction to faultsState Machine describes the actions to be taken by the node dependent on current st
25、ate and input message.Only message with highest priority will pass through the filtering.Different actions include transmission of R-APS message,blocking/unblocking a port,flushing the FDB,switching current state of node,and starting/stopping timers.,19,State Machine,FDB flushing will clear all of t
26、he learned filtering rules within the node.Current Recommendation includes basic optimization only flushing once on fault discovery and once on recovery.DNF status flag is for future definition,20,Switching Triggers,Detection/Clearing of SF(Signal Fail):SF:Loss of CCM,SF signal passed up from underl
27、ying(sub)layerSwitching is performed when hold-off timer expires after detection of SF.Operators request:Lockout,Forced switch,Manual switch,Clear(for future specification)Remote request:Switching request indicated in received R-APS information from the other node.Protection switching algorithm is b
28、ased on priorities assigned to all triggers,21,Ethernet Rings and the RPL,Ethernet nodes connected in a ring topology.Each node connected to two neighbors via links(E&W ports)Deterministic network topology,Avoid loops within ring by blocking a designated link(RPL)Node responsible to control the bloc
29、king state of RPL is RPL ownerRPL is unblocked during protection state and may revert to blocked during recovery,RPL,22,RPL Owner receives SF message and unblocks its end of RPL link row 3Stable State SF messages on the ring Further SF messages trigger no further action row10,B,C,D,E,F,G,A,SF,Normal
30、,Protectionstate,failure,SF,SF,A,Scenario A-Normal to Protection,Normal StateFailure Occurs Nodes C and D detect local Signal Failure condition and after respecting hold-off time and Block failed port row 1Node C and D periodically send SF message,on both ring ports,while SF condition persists.Each
31、node performs a FDB Flush when receiving the SF message,RPL Owner,B,SF,SF,C,D,E,SF,SF,SF,SF,SF,SF,F,50 ms,G,Flush,Flush,Flush,Flush,Flush,Flush,Flush,23,When node C and D expire the guard timer,they may accept the new R-APS messages that they receive.in guard timerAt expiration of WTR timer,RPL owne
32、r blocks its end of the RPL,sends,NR RB message row 11Each node that receives the NR,RB message it flushes its FDB.When Nodes C and D receive NR RB message,they remove block on their blocked ports.row 13Stable normal condition all nodes in Idle state,B,C,D,E,F,G,A,Normal,Protectionstate,recovery,fai
33、lure,Scenario B recovery,Stable SF condition Nodes C and D continue to send SF message every 5 secs.Recovery of Link failureNodes C and D detect clearing of SF condition,start guard timer and initiate periodical transmission of NR message on both ring ports.(Guard timer prevents reception of R-APS m
34、essages)row 9When the RPL Owner receives NR message,it starts the WTR timer row 14,RPL Owner,B,C,SF,SF,SF,SF,SF,SF,F,A,E,NR,NR,NR,NR,NR,RPL Blocked,NR,RPL Blocked,NR,RPL Blocked,G,NR,NR,RPL Blocked,NR,RPL Blocked,NR,RPL Blocked,NR,NR,D,Flush,Flush,Flush,Flush,Flush,Flush,Flush,50 ms,Confirmation time,H,
