ITUTG8032ERPS协议介绍PPT课件.ppt

G.8032Ethernet Ring Protection OverviewMarch, 2008ITU-T Q9 – SG 15Agenda§G.8032 Recommendation Introduction§G.8032 Objectives and Principles§G.8032 Concepts§G.8032 Protection Switching§G.8032 R-APS Messages§G.8032 Items Under Study2ITU-T SG15/Q9 G.8032 Recommendation§G.8032 Recommendation consented February 2008ŸThis 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.JANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECJANFEBMAR200620072008G.8032 Proposals G.8032 Proposals and Contributionsand ContributionsG.8032 Converged ProposalsG.8032 Converged ProposalsG.8032 ERP Work G.8032 ERP Work Item Approved in Item Approved in ITU-TITU-TG.8032 Objective, G.8032 Objective, Principles, and Principles, and Requirements SettingRequirements SettingG.8032 Recommendation G.8032 Recommendation ConsentConsent3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 standard 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.§Protection 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.4G.8032 Terms and Concepts Ring Protection Link (RPL) – Link designated by mechanism that is blocked during Idle state to prevent loop on Bridged ring RPL Owner – Node connected to RPL that blocks traffic on RPL during Idle state and unblocks during Protected state Link 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 detected No Request (NR) – No Request is declared when there are no outstanding conditions (e.g., SF, etc.) on the node Ring APS (R-APS) Messages – Protocol messages defined in Y.1731 and G.8032 Automatic Protection Switching (APS) Channel - Ring-wide VLAN used exclusively for transmission of OAM messages including R-APS messages5G.8032 Timers G.8032 specifies the use of different timers to avoid race conditions and unnecessary switching operations§WTR (Wait to Restore) Timer – Used by the RPL Owner to verify that the ring has stabilized before blocking the RPL after SF Recovery§Hold-off Timers – Used by underlying ETH layer to filter out intermittent link faultsŸFaults will only be reported to the ring protection mechanism if this timer expires6Controlling the Protection Mechanism Protection switching triggered by §Detection/clearing of Signal Failure (SF) by ETH CC OAM§Remote requests over R-APS channel (Y.1731)§Expiration of G.8032 timers R-APS requests control the communication and states of the ring nodes§Two 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 states§Idle – normal operation, no link/node faults detected in ring§Protecting – Protection switching in effect after identifying a signal fault7A.Physical topology has all nodes connected in a ringB.ERP guarantees lack of loop by blocking the RPL (link between 6 & 1 in figure)C.Logical topology has all nodes connected without a loop.D.Each link is monitored by its two adjacent nodes using ETH CC OAM messagesE.Signal Failure as defined in Y.1731, is trigger to ring protection§Loss of Continuity§Server layer failure (e.g. Phy Link Down)RPL OwnerRPLETH-CCETH-CCETH-CCETH-CCETH-CCETH-CCETH-CCETH-CCETH-CCETH-CCETH-CCETH-CCPhysical topologyLogical topology126435RPL126435Ring Idle State8Protection Switching  Link FailureA.Link/node failure is detected by the nodes adjacent to the failure.B.The nodes adjacent to the failure, block the failed link and report this failure to the ring using R-APS (SF) messageC.R-APS (SF) message triggers§RPL Owner unblocks the RPL§All nodes perform FDB flushingD.Ring is in protection stateE.All nodes remain connected in the logical topology.Physical topologyLogical topology126435RPL126435RPL126435126435RPL OwnerRPLR-APS(SF)R-APS(SF)R-APS(SF)R-APS(SF)9Protection Switching  Failure RecoveryA.When the failed link recovers, the traffic is kept blocked on the nodes adjacent to the recovered linkB.The nodes adjacent to the recovered link transmit R-APS(NR) message indicating they have no local request present C.When the RPL Owner receives R-APS(NR) message it Starts WTR timerD.Once WTR timer expires, RPL Owner blocks RPL and transmits R-APS (NR, RB) messageE.Nodes receiving the message – perform a FDB Flush and unblock their previously blocked portsF.Ring is now returned to Idle stateRPL OwnerRPLR-APS(NR)R-APS(NR)R-APS(NR)R-APS(NR)R-APS(NR, RB)R-APS(NR, RB)Physical topologyLogical topology126435RPL126435126435RPL12643510Signaling Channel Information ERP uses R-APS messages to manage and coordinate the protection switching R-APS defined in Y.1731 - OAM common fields are defined in Y.1731.§Version – ‘00000’ – for this version of Recommendation§OpCode – defined to be 40 in Y.1731§Flags – ‘00000000’ – should be ignored by ERP1234876543218765432187654321876543211MELVersion (0)OpCode (R-APS = 40)Flags (0)TLV Offset (32)5R-APS Specific Information (32 octets)..…37[optional TLV starts here; otherwise End TLV]lastEnd TLV (0)Defined by Y.1731Defined by G.8032Non-specified content11R-APS Specific Information Specific information (32octets) defined by G.8032§Request/Status(4bits) – ‘1011’ = SF | ’0000’ = NR | Other = Future§Status – RB (1bit) – Set when RPL is blocked (used by RPL Owner in NR)§Status – DNF (1bit) – Set when FDB Flush is not necessary (Future)§NodeID (6octets) – MAC address of message source node (Informational)§Reserved1(4bits), Status Reserved(6bits), Reserved2(24octets) - Future development 123487654321876543218765432187654321Request /StateReserved 1StatusNode ID (6 octets)  RBDNFStatus Reserved(Node ID)Reserved 2 (24 octets)12Items Under Study G.8032 is currently an initial recommendation that will continue to be enhanced. The following topics are under study for future versions of the recommendation:a)Interconnected rings scenarios: shared node, shared linksb)RPL blocked at both ends – configuration of the ring where both nodes connected to the RPL control the protection mechanismc)Support for Manual Switch – administrative decision to close down a link and force a “recovery” situation are necessary for network maintenanced)Support for Signal Degrade scenarios – SD situations need special consideration for any protection mechanisme)Non-revertive mode– Allows the network to remain in “recovery” configuration either until a new signal failure or administrative switchingf)RPL Displacement – Displacement of the role of the RPL to another ring link flexibly in the normal (idle) condition g)In-depth analysis of different optimizations (e.g., FDB flushing)h)Etc.13 Thank You14Backup15G.8032 Basic FunctionsFailureRobustness: Source Steering Protection 50ms Switch TimesConnectivity: Unicast, MC and BC Data Transfers Multicast FlowUnicastFlow16ERP Functionality Decomposition Inputs – Local node requests, ETH 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 RPL-Owner indication Outputs – Node functions (FDB Flushing, Block/Unblock port), sending (or stopping) R-APS messages17State Machine§Three node states –ŸInitialization – when first defining the ringŸA (Idle) – the ‘normal’ state of the ring nodes with RPL blocked and all nodes/ports workingŸB (Protecting) – when protection 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 faults§State Machine describes the actions to be taken by the node dependent on current state and input message.ŸOnly message with highest priority will pass through the filtering.ŸDifferent actions include – transmission of R-APS message, blocking/unblocking a port, flushing the FDB, switching current state of node, and starting/stopping timers.Inputs OutputsNode StateHigh Priority requestRow#ActionsNext node state*Initialization0Stop guard timerStop WTR timerIf RPL Owner: Block RPL portUnblock non-RPL port Tx R-APS (NR, RB)Else: Block both ports Stop Tx R-APSBA (Idle)Local SF1Block failed port;Unblock non Failed port;Tx R-APS(SF);Flush FDB;BLocal Clear SF2No action AR-APS(SF)3Unblock non Failed port;Stop Tx R-APSIf not “DNF” Flush FDB; BWTR Expires4No action AWTR Running5No action AR-APS(NR, RB)6Unblock non-RPL port AR-APS(NR)7No actionA18State MachineInputs OutputsNode StateHigh Priority requestRow#ActionsNext node stateB(Protecting)Local SF8Block failed port;Unblock non Failed port;Stop WTR;Tx R-APS(SF);BLocal Clear SF9Start guard timer,Tx R-APS(NR), BR-APS(SF)10Stop WTR,Unblock non Failed port,Stop Tx R-APSBWTR Expires11Block RPL port,Unblock non-RPL portTx R-APS (NR,RB)Flush FDB,AWTR Running12No action BR-APS(NR, RB)13If not RPL Owner: Unblock both ports, Stop Tx R-APS, If not “DNF” Flush FDB AR-APS(NR)14If RPL Owner: Start WTRB§FDB flushing will clear all of the learned filtering rules within the node.ŸCurrent Recommendation includes basic optimization – only flushing once on fault discovery and once on recovery.ŸDNF status flag is for future definition19Switching Triggers Detection/Clearing of SF (Signal Fail): ŸSF: Loss of CCM, SF signal passed up from underlying (sub)layerŸSwitching is performed when hold-off timer expires after detection of SF. Operator’s request: ŸLockout, Forced switch, Manual switch, Clear (for future specification) Remote request: ŸSwitching request indicated in received R-APS information from the other node.Protection switching algorithm is based on priorities assigned to all triggers20Ethernet Rings and the RPL§Ethernet nodes connected in a ring topology.ŸEach node connected to two neighbors via links (E & W ports)ŸDeterministic network topology§Avoid loops within ring by blocking a designated link (RPL)ŸNode responsible to control the blocking state of RPL is RPL ownerŸRPL is unblocked during protection state and may revert to blocked during recovery•RPL21E.RPL Owner receives SF message and unblocks its end of RPL link [row 3]F.Stable State – SF messages on the ring G.Further SF messages trigger no further action [row10]BCDEFGASFNormalProtectionstatefailureR-APS ch blockClient ch blockSFSFAScenario A - Normal to ProtectionA.Normal StateB.Failure Occurs C.Nodes C and D detect local Signal Failure condition and after respecting hold-off time and Block failed port [row 1]D.Node C and D periodically send SF message, on both ring ports, while SF condition persists. Each node performs a FDB Flush when receiving the SF messageRPL OwnerBMessage sourceSFSFCDESFSFSFSFSFSFF50 msGRPLFlushFlushFlushFlushFlushFlushFlush22E.When node C and D expire the guard timer, they may accept the new R-APS messages that they receive. [in guard timer]F.At expiration of WTR timer, RPL owner blocks its end of the RPL, sends, NR RB message [row 11]G.Each 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 13]H.Stable normal condition all nodes in Idle stateBCDEFGRPLANormalProtectionstaterecoveryfailureScenario B recoveryA.Stable SF condition Nodes C and D continue to send SF message every 5 secs. B.Recovery of Link failureC.Nodes 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 messages) [row 9]D.When the RPL Owner receives NR message, it starts the WTR timer [row 14]RPL OwnerBCSFSFSFSFSFSFFAENRNRNRNRNR, RPL BlockedNR, RPL BlockedNR, RPL BlockedGNRNR, RPL BlockedNR, RPL BlockedNR, RPL BlockedNRNRDFlushFlushFlushFlushFlushFlushFlush50 msConfirmation timeH23部分资料从网络收集整理而来，供大家参考，感谢您的关注！。