RFC 6805 on The Application of the Path Computation Element Architecture to the Determination of a Sequence of Domains in MPLS and GMPLS

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        RFC 6805

        Title:      The Application of the Path 
                    Computation Element Architecture 
                    to the Determination of a 
                    Sequence of Domains in 
                    MPLS and GMPLS 
        Author:     D. King, Ed.,
                    A. Farrel, Ed.
        Status:     Informational
        Stream:     IETF
        Date:       November 2012
        Mailbox:    daniel@olddog.co.uk, 
                    adrian@olddog.co.uk
        Pages:      33
        Characters: 77669
        Updates/Obsoletes/SeeAlso:   None

        I-D Tag:    draft-ietf-pce-hierarchy-fwk-05.txt

        URL:        http://www.rfc-editor.org/rfc/rfc6805.txt

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 PCE-based 
Computation (BRPC) procedure 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.  This document is not an Internet Standards Track 
specification; it is published for informational purposes.

This document is a product of the Path Computation Element Working Group of the IETF.

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