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

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

• Ning So (ning.so_at_verizonbusiness.com)
• Mach Chen (mach_at_huawei.com)
• Ville Hallivuori (ville.hallivuori_at_tellabs.com )

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BFD Enhancement Overview

• Relax 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-pa
  th-specified-lsp-ping)
• Only one BFD session is provisioned onto a
  bidirectional Path
• Controlled 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 description
• multiple uni-directional LSPs exist between
  Router 1 2, carrying different type of services
• Multiple bi-directional LSPs exist between Node
  AB, 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 failure
• In 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 process
• No need to log into both routers reduces customer
  down time and increase network availability
• It 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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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
  comparison
• Clarified 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 added
• Describes 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?