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The Case for the ‘A’ bit in the MPLS/PW PID (redux) draft-allan-mpls-a-bit-00.txt

The Case for the ‘A’ bit in the MPLS/PW PID (redux) draft-allan-mpls-a-bit-00.txt. Dave Allan Nortel Networks. Motivations. MPLS reserved label functions do not “fate share” with associated LSPs/PWs in the presence of ECMP. Motivations/2.

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The Case for the ‘A’ bit in the MPLS/PW PID (redux) draft-allan-mpls-a-bit-00.txt

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  1. The Case for the ‘A’ bit in the MPLS/PW PID (redux) draft-allan-mpls-a-bit-00.txt Dave Allan Nortel Networks draft-allan-mpls-a-bit-00.txt

  2. Motivations • MPLS reserved label functions do not “fate share” with associated LSPs/PWs in the presence of ECMP draft-allan-mpls-a-bit-00.txt

  3. Motivations/2 • Directions in proactive network supervision complicate fault correlation • Faults may be detected by multiple, un-coordinated means (e.g. ping, RSVP-Hello, Y.17fec-cv etc.) • Desirable to “increase locality” of detection of path problems. draft-allan-mpls-a-bit-00.txt

  4. Motivations/3 • Increasing locality of fault detection requires intermediate NEs to examine OAM flows • Traceroute is one alternative (albeit heavyweight) • MPLS router alert has limitations (RA as top label may not have implementation commonality with forwarding label as top label) draft-allan-mpls-a-bit-00.txt

  5. Motivations/4 • Use of label stacking for demarcation has limitations • Useful for security reasons • Ideal is to push testing out as close to the CE as possible • Ability to do OAM on a portion of an LSP or PW requires intermediate NEs to examine OAM flows draft-allan-mpls-a-bit-00.txt

  6. Motivations/5 • IMHO progressive divergence of PWs and LSPs • Driving commonality has utility • Multi-hop or “spliced” PWs may ultimately require more common functionality with LSPs, but currently would have to use different mechanisms to achieve those functions in non MPLS networks draft-allan-mpls-a-bit-00.txt

  7. MPLS/PW PID • Perceived as a point of commonality between PWs and MPLS • Allows control and OAM flows to be muxed with LSPs/PWs • Currently only has e2e significance • Addresses ECMP fate sharing for e2e OAM and control flows draft-allan-mpls-a-bit-00.txt

  8. MPLS/PW PID • ‘A’ bit proposal is about migrating reserved label functions to the PID • Define alternative to Router Alert is one step • Other functions are FFS 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 1|A| rsvd. | PA | Protocol ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ draft-allan-mpls-a-bit-00.txt

  9. Observations • Data plane change • Issues with backwards compatibility to be worked • Example raised yesterday, what if payload aliases as RA • Answer: something different that payload aliasing as IP draft-allan-mpls-a-bit-00.txt

  10. Summary • ECMP breaks reserved labels • Reserved labels do not exist for PWs • PID+’A’-bit is ECMP friendly alternative for MPLS and PWs • Eases convergence of MPLS and PW OAM and control. • Per LSP/PW functions defined via CW extensions draft-allan-mpls-a-bit-00.txt

  11. Questions? draft-allan-mpls-a-bit-00.txt

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