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MPLS-TP BFD for CC-CV proactive and RDI functionalities

MPLS-TP BFD for CC-CV proactive and RDI functionalities. draft-asm-mpls-tp-bfd-cc-cv-02 MPLS WG, 77th IETF - Anaheim . 1. Authors. Annamaria Fulignoli (Ericsson) Sami Boutros (Cisco Systems) Martin Vigoureux (Alcatel-Lucent). Current contributors. George Swallow ( Cisco Systems)

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MPLS-TP BFD for CC-CV proactive and RDI functionalities

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  1. MPLS-TP BFD for CC-CV proactive and RDI functionalities draft-asm-mpls-tp-bfd-cc-cv-02 MPLS WG, 77th IETF - Anaheim 1

  2. Authors • Annamaria Fulignoli (Ericsson) • Sami Boutros (Cisco Systems) • Martin Vigoureux (Alcatel-Lucent)

  3. Current contributors • George Swallow (Cisco Systems) • David Ward (Juniper)

  4. Why draft-asm-mpls-tp-bfd-cc-cv • Specify the BFD extension and behavior to satisfy the CC, proactive CV monitoring and the RDI functionality. • BFD behavior needs to be PROFILED ( it’s not only a trivial packet extension) in order to: • meet all MPLS-TP requirement • to have a very simple and fast tool as transport operator require

  5. Problem Statement In the case of bidirectional LSPs, if a bidirectional BFD session is used, it will go down in the event of a failure (or mis-configuration) affecting a single direction, while the expected behaviour, from a transport point of view, is that the up-and-running other direction is still polled at the configured rate. eet at IETF Registration desk

  6. B A Solution Overview Use “Unidirectional” BFD sessions • On bidirectional path two unidirectional BFD sessions MUST be configured, one for each direction of the bidirectional path to be monitored. • Each MEP is aware of the relationship among the MEP source function and MEP sink function of the two unidirectional BFD sessions. • The unidirectional BFD uses the state machine defined in draft-katz-ward-bfd-multipoint-02 • The M bit MUST be always set to 1. • Slow rate startup requires further analysis and is under study.

  7. Unidirectional BFD session M =1 ; Tx = 10 ms; Rx = 0; My Dis = 10; Your = 0; State = UP; Diag = 0 MEP A MEP B M =1 ; Tx = 10 ms; Rx = 0; My Dis= 20; Your = 0; State = UP; Diag = 0 B Sink direction goes in Down State due to a failure from A direction M =1 ; Tx = 10 ms; Rx = 0; My Dis = 10; Your = 0; State = UP; Diag = 0 MEP A MEP B M =1 ; Tx = 10 ms; Rx = 0; My Dis= 20; Your = 0; State = UP; Diag = 1 MEP B needs tosend RDI

  8. Solution applicability • on p2p bidirectional (corouted or associated) • but also on p2p unidirectional and p2mp • RDI simply not required

  9. Non exclusive solution • Possible to run existing BFD • The state machine and behavior are as detailed in draft-ietf-bfd-base for asynchronous BFD. • M bit set to 0

  10. Two modes of operation • Two modes of operation (as for previous draft versions) • CC • Existing ACH codepoint (0x0007) - BFD w/o IP/UDP • Supports CC & RDI • CV/CC • New ACH codepoint • Header contains the Source MEP Identifier (unique per transport path) • BFD control packet format is identical to CC mode • Supports CV & RDI (Implicit CC) • Both apply to PWs, MPLS LSPs (including tandem connection monitoring), and sections

  11. Demultiplexing and the Discriminator Fields • MPLS labels at peer MEPs are used to provide context for the received BFD packets. • On MPLS-TP context the discriminator values have either only local or no significance.

  12. Next Steps • Add more implementation details: • Behaviour of MEP receiving a BFD packet with AdminDown State • Complete the security section • Address comments received • Ask for workgroup adoption

  13. QUESTIONS ? THANK YOU

  14. B A APPENDIX: why going at slow rate when transit from DOWN to UP state does not meet all MPLS-TP requirement • Bidirectional LSP with node A and node B configured MEPs • TX and RX is fixed by operator at 10 msec; detection time multiplier = 3 • Unidirectional failure occurs from node A to node B • In this scenario, node B goes in DOWN state while node A goes in DOWN and than soon in INIT state as it still receives right packets from node B. • If node B starts sending at 1 second rate, as requested by draft-ietf-bfd-base, node A receives right BFD packets from node B , but just one packet per second while the configured detection timeout is 3 * 10 ms . As a consequence: • MEP A flips between DOWN and INIT State due to intermittent Loss Of connectivity defect condition. • a false failure is detected on A node and if protection switching is enabled A switches to protection path even if the worker path is good. • The conclusion is that the Unidirectional protection switching, that is a MUST requirement for MPLS-TP, is not supported .

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