Requirements for P2MP Extensions to LDP draft-leroux-mpls-mp-ldp-reqs-02.txt

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Requirements for P2MP
Extensions to LDP
draft-leroux-mpls-mp-ldp-reqs-02.txt


Jean-Louis Le Roux
(France Telecom)
Thomas Morin (France Telecom)
Vincent Parfait (Equant)
Luyuan Fang (ATT)
Lei Wang (Telenor)
Yuji Kamite (NTT Communications)
Shane Amante (Level 3 Communications)

• IETF 64, Vancouver, MPLS WG, 11/08/2005

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Motivations and Objectives (Reminder)

• LDP largely deployed for setting up unicast LSPs
  in MPLS VPN networks
• Emerging requirements for supporting multicast
  traffic delivery within these MPLS VPN networks
• A relevant approach for multicast traffic
  delivery over a LDP enabled MPLS backbone LDP
  extensions for setting up Point-To-Multipoint
  LSPs (P2MP LSPs)
• This draft focuses on the LDP approach for
  setting up P2MP LSPs
• It lists a detailed set of requirements for P2MP
  extensions to LDP
• To be used as guidelines when specifying LDP
  extensions

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Requirements summary

• MUST allow setting up P2MP LSPs
• MUST define a FEC suitable for P2MP forwarding
• SHOULD rely on unicast routing table for setting
  up MPLS shortest path trees
• SHOULD support leaf initiated approach for LSP
  setup and modification
• SHOULD avoid data duplication
• SHOULD avoid routing loops
• SHOULD minimize recovery upon network failure
• SHOULD avoid both packet loss and packet
  duplication during rerouting upon planned
  maintenance or metric change Tension?
• MUST avoid traffic replication on LAN interfaces
• MUST Support encapsulation in P2P and P2MP TE
  tunnels
• MUST support IPv4/IPv6 (control and forwarding)
• MUST support multi-area LSPs
• OAM Requirements
• MIB module, connectivity checking and path
  tracing tool, fast failure detection tool
• MUST support Graceful Restart and Fault Recovery
• SHOULD scale independently of the number of
  leaves
• SHOULD allow setting up P2MP LSPs over a transit
  non branch legacy LSR
• MUST not impede the operations of unicast LSPs

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Changes since last version

• Added an application scenario
• Multicast VPN traffic delivery on a LDP-enabled
  MPLS backbone
• Clarified routing requirements
• Clarified OAM requirements
• Need for extensions of P2MP LSP-Ping to LDP P2MP
  LSPs
• Need for a fast data plane failure detection
  mechanism for P2MP LDP LSPs
• Detailed requirements addressed in the P2MP MPLS
  OAM draft
• Added orders of magnitude of the expected Trees
  
• Leaves / Tree
• Extracted from the Multicast L3 VPN survey (L3VPN
  WG)
• Added some text on shared trees and MP2MP LSPs
• Some rewordings for the sake of clarity

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Remaining issues (1)

• Need to complement the requirements related to
  LAN interfaces, when there are several candidate
  upstream LSRs
• The solution MUST allow selecting a single
  upstream for a given P2MP LSP on a LAN
• The solution SHOULD support for efficient
  balancing of a set of P2MP LSPs among a set of
  candidates upstream LSRs on a LAN interface
• Need to detail routing requirements
• Consensus among SPs on this draft that P2MP LDP
  routing SHOULD rely on the unicast RIB for
  setting up MPLS SPT, and not require an IP
  multicast routing protocol
• We need to detail the rationales for this
  requirement
• This requires more discussions and WG feedback

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Remaining issues (2)

• About shared trees
• Two main approaches for setting up shared trees
  in an MPLS network
• MPLS level Multipoint-to-Multipoint LSPs (MP2MP
  LSPs) gt need for specific LDP procedures
• Application level Combination of a MP2P LSPs
  with a P2MP LSP (see Multicast 2547 ID)
• Not clear analysis of the pros and cons of the
  two approaches at the time being
• Do we need both approaches?
• What would be the gain of the MP2MP approaches
  versus the added complexity on LDP?
• This is why the requirement for MP2MP LSPs
  remains OPTIONAL
• Of course this may evolve based on WG feedback

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Next steps

• Need for WG feedback, particularly on open issues
• A WG polling in Paris showed a significant
  interest for this work
• WG doc?
• To chairs What is the status of the WG charter
  update process?