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BFD for MPLS LSPs Enhancement draft-chen-mpls-bfd-enhancement-01.txt

Ning So (ning.so@verizonbusiness.com) Mach Chen (mach@huawei.com)Ville Hallivuori (ville.hallivuori@tellabs.com )

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BFD Enhancement OverviewRelax the rule of “One BFD session per FEC” to “One BFD session per LSP or pair of LSPs”.

Reduce the number of BFD sessions

Allows LSP ingress to signal the desired return path for any BFD session

Utilizes the Return-Path-Specified capability defined in RPS-LSP-PING (draft-chen-mpls-return-path-specified-lsp-ping)

Only one BFD session is provisioned onto a bidirectional PathControlled by a new TLV: Session Control TLV

The node with larger IP SHOULD initiate the signaling

Allows one BFD session to be used as protection trigger for a pair of unidirectional LSPs

The forwarding and returning path of the LSP pair are congruent

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Use Case for Enhanced BFD

Use case condition descriptionmultiple uni-directional LSPs exist between Router 1 & 2, carrying different type of servicesMultiple bi-directional LSPs exist between Node A&B, carried on diverse physical transport paths

Return-path-specified BFD enhancement can simplify the BFD session provisioning process

No need to log into both routers in order to deterministically select the physical paths on which the operators want to detect failureIn this case, the operator can provision 3 BFD sessions onto 6 uni-directional LSPs (3 in each direction) where those LSPs are carried on 3 diverse path. The time savings can be very significant when activating a new router in a large network where full-mesh LSPs provisioning are required to support the services (e.g. VPLS) carried on the new router

Return-path-specified BFD enhancement can simplify the trouble shoot processNo need to log into both routers reduces customer down time and increase network availabilityIt is especially useful when the remote router is not accessible (belong to another carrier or all login sessions occupied), or the remote router is of different equipment vendor on which the trouble shooting operator is not trained

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Uni-Directional LSP

Bi-Directional LSPMultiple LSP

ROUTER 1

100GE

ROUTER 2NODE A NODE B

100GE

… ……

…

…

Diverse Transport Paths

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Differences between version 0 and version 1

Following changes were made on Session establishment section based on the comments from Vishwas Manral:

Proposed to use Source Address TLV to carry the IP address of the initiator when IP forwarding is disabled (in MPLS-TP scenario) for IP address comparisonClarified the process of BFD control packets when a single BFD session is provisioned to a bidirectional path

• the initiator (ingress) MUST not send BFD packets before echo reply received

• Ensure that the BFD session is complete for both directions before any BFD control packets are sent over the session

A new section (Section 5 Encapsulation) is addedDescribes how to encapsulate the BFD control packets transmitted over the return LSP

Other minor editorial changes for error correction and clarification purposes

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Acknowledgements

Authors would like to thank Greg Mirsky, Vishwas Manral, Adrian Farrel, Peter Ashwood-smith and Xinchun Guo for their reviews and great input

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Next Step

Should this draft progress within MPLS WG draft or should it be moved to BFD WG?