Encoding of Objective Functions in Path Computation Element (PCE) communication and discovery protocols
France Telecom
The computation of one or a series of Traffic Engineering Label
Switched Paths (TE LSP) in MultiProtocol Label Switching (MPLS) and
Generalized MPLS (GMPLS) networks, is subject to a set of one or more
specific optimization criteria(s), referred to as an objective
function (e.g. minimum cost path, widest path, etc.). A Path
Computation Element (PCE) may support one or multiple objective
functions, and it is desired for a Path Computation Client (PCC) to
automatically discover the set of objective functions supported by a
PCE. Furthermore, it may be useful for a PCC to specify in a path
computation request the required objective function used by the PCE
to compute a TE LSP or a set of TE LSPs. Thus the aim of this
document is to define extensions to the PCE Discovery (PCED) TLV
carried within the IS-IS Router Capability TLV and the OSPF Router
Information LSA so as to allow a PCC to discover the set of objective
functions supported by a PCE. Extensions to the PCE communication
Protocol (PCEP) are also specified allowing a PCC to indicate in a
path computation request the required objective function and a PCE to
indicate in a path computation reply the objective function actually
applied.