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ECMP with RSVP-TE

ECMP with RSVP-TE. Kireeti Kompella Juniper Networks. Outline. Current situation LDP vs. TE ECMP NxTE LSPs vs. TE ECMP MLSP Signaling Next steps. Current Situation. A n MPLS network relies on an underlying LSP mesh connecting all edge devices In principle, this could be IP tunnels

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ECMP with RSVP-TE

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  1. ECMP with RSVP-TE Kireeti Kompella Juniper Networks

  2. Outline • Current situation • LDP vs. TE ECMP • NxTE LSPs vs. TE ECMP MLSP • Signaling • Next steps

  3. Current Situation • An MPLS network relies on an underlying LSP mesh connecting all edge devices • In principle, this could be IP tunnels • This may be based on LDP or RSVP-TE, or sometimes a combination of LDP on the edge and RSVP-TE in the core • There are a number of attributes that dictate the design

  4. LSP Design Attributes

  5. Either/or … Why Not Both? • Can one create an underlying mesh of tunnels that has both TE and ECMP? • Yes! • Introduce the notion of a “multi-path” TE LSP signaled using RSVP • Several “sub-LSPs” under one container tunnel • Note that the state required for RSVP-TE is still higher (O(N^2)) than that for LDP (O(N))

  6. Illustration (LDP vs. TE ECMP) 200 Mbps LSP from A to B 25 40 100 160 A B 100 40 100 40

  7. NxTE LSPs vs. TE ECMP MLSP 200 Mbps MLSP from A to B vs. 5 40Mbps TE LSPs A B

  8. Discussion • NxLSPs requires N things to provision and manage; an MLSP is a single object with N sub-objects • An MLSP with N sub-LSPs may (depending on the topology) have significantly less state than N LSPs • The use of equi-bandwidth sub-LSPs can also significantly reduce state

  9. Discussion • Computing the NxLSPs is done pretty much independent • The number and placement of the LSPs may not be optimized for the purpose of ECMP • Failure of one of the N LSPs means that the overall bandwidth drops (e.g., by 40Mbps) • Failure of one sub-LSP can be compensated by the head end bumping up the bandwidths of the rest

  10. Signaling • The current draft talks a little bit about signaling • Basic idea: signal N sub-LSPs, and tie them together via a Session object to form an MLSP • Introduce the idea of “equi-bandwidth” sub-LSPs • If this draft is of interest, the signaling piece would probably need more work • Have to work out how FRR and DiffServ-awareness work in the context of MLSPs

  11. Next Steps • Get a sense of how useful this is

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