The Application of the Path Computation Element Architecture to the Determination of a Sequence of Domains in MPLS and GMPLS

Document Type Replaced Internet-Draft (individual)
Authors Daniel King  , Adrian Farrel  , Quintin Zhao  , Fatai Zhang 
Last updated 2011-10-17 (latest revision 2011-04-18)
Replaces draft-king-pce-brpc-app
Replaced by RFC 6805
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


Computing optimum routes for Label Switched Paths (LSPs) across multiple domains in MPLS Traffic Engineering (MPLS-TE) and GMPLS networks presents a problem because no single point of path computation is aware of all of the links and resources in each domain. A solution may be achieved using the Path Computation Element (PCE) architecture. Where the sequence of domains is known a priori, various techniques can be employed to derive an optimum path. If the domains are simply-connected, or if the preferred points of interconnection are also known, the Per-Domain Path Computation technique can be used. Where there are multiple connections between domains and there is no preference for the choice of points of interconnection, the Backward Recursive Path Computation Procedure (BRPC) can be used to derive an optimal path. This document examines techniques to establish the optimum path when the sequence of domains is not known in advance. The document shows how the PCE architecture can be extended to allow the optimum sequence of domains to be selected, and the optimum end-to-end path to be derived through the use of a hierarchical relationship between domains.


Daniel King (
Adrian Farrel (
Quintin Zhao (
Fatai Zhang (

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