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  1. Encoding of Objective Functions in PCE Communication and Discovery Protocolsdraft-leroux-pce-of-00.txtJ.L. Le Roux (France Telecom) J.P. Vasseur (Cisco Systems) Y. Lee (Huawei) IETF 68, PCE WG, Prague

  2. Overview • The computation of one or a series of TE-LSPs is subject to an objective function (OF) • Unsynchronized computations: Minimum cost path, shortest widest path, widest shortest path, etc. • Synchronized computation: Minimize the load on the most loaded link, minimize the global bandwidth consumption, etc. • As spelled out in RFC 4674, it may be useful for a PCC to discover the set of objective functions supported by a PCE • As spelled out in RFC 4657, a PCC must be able to indicate in a request a required objective function as well as optional parameters • This draft covers these requirements • PCED extensions allowing a PCE to advertise a list of supported OF • PCEP extensions allowing to carry an OF in a request/response

  3. PCE OF Code Point Registry • An Objective Function is identified by a 16 bit code point • A common Objective Function Code Point Registry is defined for both PCE communication and discovery protocols • To be managed by IANA • Values 32768-65535 for private use • A document that defines an objective function will request a code point from this registry • e.g. draft-lee-pce-concurrent-optimization

  4. PCE Discovery Extensions • IS-IS and OSPF based PCE Discovery defined in draft-ietf-pce-disco-proto-{isis | ospf} • PCED TLV carried in OSPF Router Information LSA and IS-IS Router Capability TLV • Extension to PCED TLV, that allows a PCE to advertise a list of supported objective functions • A new sub-TLV of the PCED TLV is defined: the OF-List sub-TLV • carries a list of 16-bit Objective Function identifiers • Indicates objective functions supported by the PCE

  5. PCEP Extensions • A new PCEP Object is defined, the OF Object, to be carried in PCReq and PCRep messages • carries a 16-bit objective function identifier + Optional TLVs to encode parameters • When carried in a PCReq it indicates a desired/required objective function • If P bit = 1 this is required, else this is desired • If the OF object applies to a synchronize computation, it MUST be carried just after the SVEC object and MUST not be repeated for each elementary request • When carried in a PCRep it indicates the objective function actually applied • Useful if there is no OF in the PCReq or if the PCE applied another OF than the desired one • A new flag defined in the RP object, used in a PCReq to indicate that the objective function that will be actually applied by the PCE should be provided in the PCRep • New PCEP error codes/values • Error code "Objective Function Error". Values: unknown/unsupported OF • New values for the error code "Policy Violation": "Unauthorized OF", "OF bit in RP"

  6. Next Steps • Straightforward PCED and PCEP extensions • Shall we define objective functions in this draft? • Jerry asked for the definition of objective functions listed in 4657 • Discussion on the list and offline • Conclusion => They will be added in next revision • Need for WG feedback • Adopt as WG doc?

  7. ThanksQuestions?