Reoptimization of MPLS Traffic Engineering loosely routed explicit LSP paths
NTT Communications Corporation
NTT Communications Corporation
The aim of this document is to propose a mechanism for the reoptimization of MPLS Traffic Engineering loosely routed explicit LSP paths. A loosely routed explicit LSP path is a path specified as a combination of strict and loose hop(s) that contains at least one loose hop and zero or more strict hop(s). The path calculation (which implies ERO expansion) to reach a loose hop is made on the previous hop defined in the TE LSP path. This draft proposes a mechanism that allows: - The TE LSP Head-end LSR to trigger a new ERO expansion on every hop having a next hop defined as a loose hop, - An LSR to signal to the TE LSP head-end that a better path exists to reach a loose hop (than the current path in use). A better path is defined as a path with a lower cost, where the cost is determined by the metric used to compute the path. This primarily applies to inter-area TE LSPs and inter-AS TE LSPs when the path is defined as a list of loose hops (generally the loose hops are the ABRs/ASBRs) but the following mechanism is also applicable to any loosely routed explicit path within a single routing domain.