IETF 68, PCE WG, Prague

Encoding of Objective Functions in PCE Communication and Discovery Protocols draft-leroux-pce-of-00.txt

J.L. Le Roux (France Telecom) J.P. Vasseur (Cisco Systems) Y. Lee (Huawei)

OverviewThe 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 requirementsPCED extensions allowing a PCE to advertise a list of supported OFPCEP extensions allowing to carry an OF in a request/response

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 IANAValues 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

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-TLVcarries a list of 16-bit Objective Function identifiersIndicates objective functions supported by the PCE

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 functionIf P bit = 1 this is required, else this is desiredIf 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 appliedUseful 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/valuesError code "Objective Function Error". Values: unknown/unsupported OFNew values for the error code "Policy Violation": "Unauthorized OF", "OF bit in RP"

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 4657Discussion on the list and offlineConclusion => They will be added in next revision

Need for WG feedback

Adopt as WG doc?

Thanks

Questions?