1. © 2006 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 1 MPLS –TP Fault OAM draft-ietf-mpls-tp-fault-01 George Swallow swallow@cisco.com IETF77 March 2010

2. © 2006 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 2 Why MPLS-TP OAM? Goals Support the requirements of transport Build better OAM for MPLS Be compatible with deployed MPLS equipment There is existing MPLS equipment that cannot run BFD at 3.3, 10 or even 50 ms at scale There is a desire among owners of that equipment for faster failover

3. © 2006 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 3 Hold off Timer? In Sonet equipment AIS is sent continuously Lack of an LDI signal is handled with a hold-off timer which allow time for the server layer to recover before the client layer reacts This prevents unnecessary protection switches In MPLS-TP AIS is sent at a max rate of 1 per sec and does not time out for 3.5 seconds There appears to be no reasonable and useful timer setting for a hold-off timer! This is the motivation for the Link Down Indication

4. © 2006 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 4 Link Down Indication (LDI) LDI carries all the same semantics as AIS plus the indication of a hard failure In fact it would be fine to have just an AIS message and a flag for LDI Flag clear = Protecting State; Flag set = Unavailable State LDI is only need when CC is running slowly If CC is running fast (detect time ~500 ms or less) then LDI is treated just like AIS

5. © 2006 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 5 Link Down Indication (LDI) The decision to send AIS or LDI is driven from the APS state LDI must be sent whenever the server layer enters the unavailable state When LDI is received by an MPLS-TP LSPs MEP it is used to Suppresses alarms due to any CC failure – just like AIS If the LSP is protected and CC is running slowly, and if no CC failure has occurred (i.e. BFD is up), may trigger path protection

6. © 2006 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 6 AIS / LDI Fault Generation Client LSP Server Working LSP Server Protection LSP

7. © 2006 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 7 Case 1: An unprotected link Server Path is unprotected Control function sets Server MEP W to send LDI on CC failure Server Path W Server MEP W Client Path Server APS/Control

8. © 2006 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 8 Case 2: Both Working and Protection are Up CC functions are reporting that both W and P are up APS is in the Normal State Control Function sets both MEPs to send AIS on CC failure Server LSP P Server LSP W Server MEP P Server MEP W Client Path Server APS/Control

9. © 2006 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 9 Case 3: Protection Up, Working Fails Server LSP W fails, Server MEP W begins sending AIS Server LSP P Server LSP W Server MEP P Server MEP W Client LSP X Server APS/Control

10. © 2006 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 10 Case 3: Protection Up, Working Fails Server LSP W fails, Server MEP W begins sending AIS APS / Control Function moves selector to Protection LSP AIS ceases to be inserted in Client LSP APS enters Protecting State, Control Function sets Server MEP P to send LDI Server LSP P Server LSP W Server MEP P Server MEP W Client LSP X Server APS/Control

11. © 2006 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 11 Case 4: Working has failed; Protection Fails Server LSP P fails, Server MEP P begins sending LDI APS enters Unavailable State Server LSP P Server LSP W Server MEP P Server MEP W Client LSP X Server APS/Control X

12. © 2006 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 12 Case 5: Protection Up; Working comes Up Server MEP W CC fault clears APS enters Normal State APS / Control Function sets Server MEP P to send AIS Server LSP P Server LSP W Server MEP P Server MEP W Server APS/Control Client LSP X

13. © 2006 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 13 Default sending behavior OpCode set to AIS, LDI or LKR R-flag set to zero (not used) Refresh Timer default value is 1 sec Message continuously transmitted until condition clears

14. © 2006 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 14 For existing MPLS equipment, receiving control packets can be taxing, particularly if many LSP terminating at a node are receiving fault messages Solution is to allow back-off after transmitting 3 times at one second Optional Sending Behavior

15. © 2006 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 15 OpCode set to AIS, LDI or LKR R-flag set to zero Refresh Timer set to configured value (default 20 sec) Message transmitted three times at one second intervals Message continuously transmitted according to refresh timer until condition clears Optional Sending Behavior

16. © 2006 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 16 Used when refresh timer is set long When fault / lock condition clears Set R-bit to one Transmit three times at refresh interval of 1 sec Optional Clearing Behavior

17. © 2006 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 17 Next Steps Address Liaison comments Incorporate other comments Republish