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

Internet Engineering Task Force (IETF)                      D. King, Ed.
Request for Comments: 6805                                A. Farrel, Ed.
Category: Informational                               Old Dog Consulting
ISSN: 2070-1721                                            November 2012

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

Abstract

   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.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

King & Farrel                 Informational                     [Page 1]
RFC 6805                 PCE Hierarchy Framework           November 2012

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6805.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................4
      1.1. Problem Statement ..........................................5
      1.2. Definition of a Domain .....................................5
      1.3. Assumptions and Requirements ...............................6
           1.3.1. Metric Objectives ...................................6
           1.3.2. Diversity ...........................................7
                  1.3.2.1. Physical Diversity .........................7
                  1.3.2.2. Domain Diversity ...........................7
           1.3.3. Existing Traffic Engineering Constraints ............7
           1.3.4. Commercial Constraints ..............................8
           1.3.5. Domain Confidentiality ..............................8
           1.3.6. Limiting Information Aggregation ....................8
           1.3.7. Domain Interconnection Discovery ....................8
      1.4. Terminology ................................................8
   2. Examination of Existing PCE Mechanisms ..........................9
      2.1. Per-Domain Path Computation ................................9
      2.2. Backward-Recursive PCE-Based Computation ..................10
           2.2.1. Applicability of BRPC When the Domain Path
                  is Not Known .......................................11
   3. Hierarchical PCE ...............................................12
   4. Hierarchical PCE Procedures ....................................13
      4.1. Objective Functions and Policy ............................13
      4.2. Maintaining Domain Confidentiality ........................14

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