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

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

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  1. Requirements for P2MP Extensions to LDP draft-leroux-mpls-mp-ldp-reqs-02.txtJean-Louis Le Roux (France Telecom)Thomas Morin (France Telecom) Vincent Parfait (Equant) Luyuan Fang (AT&T) Lei Wang (Telenor) Yuji Kamite (NTT Communications) Shane Amante (Level 3 Communications) IETF 64, Vancouver, MPLS WG, 11/08/2005

  2. 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

  3. 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 • MAY support Multipoint-to-Multipoint LSPs (MP2MP LSPs)

  4. 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

  5. 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

  6. 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) => 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

  7. 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?

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