Path Computation Element Communication Protocol (PCECP) Specific Requirements for Inter-Area MPLS and GMPLS Traffic Engineering
RFC 4927
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RFC - Informational
(June 2007; No errata)
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2015-10-14
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IETF
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RFC 4927 (Informational)
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Ross Callon
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Network Working Group J.-L. Le Roux, Ed.
Request for Comments: 4927 France Telecom
Category: Informational June 2007
Path Computation Element Communication Protocol (PCECP) Specific
Requirements for Inter-Area MPLS and GMPLS Traffic Engineering
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
For scalability purposes, a network may comprise multiple Interior
Gateway Protocol (IGP) areas. An inter-area Traffic Engineered Label
Switched Path (TE-LSP) is an LSP that transits through at least two
IGP areas. In a multi-area network, topology visibility remains
local to a given area, and a head-end Label Switching Router (LSR)
cannot compute an inter-area shortest constrained path. One key
application of the Path Computation Element (PCE)-based architecture
is the computation of inter-area TE-LSP paths. The PCE Communication
Protocol (PCECP) is used to communicate computation requests from
Path Computation Clients (PCCs) to PCEs, and to return computed paths
in responses. This document lists a detailed set of PCECP-specific
requirements for support of inter-area TE-LSP path computation. It
complements the generic requirements for a PCE Communication
Protocol.
Le Roux Informational [Page 1]
RFC 4927 PCECP Requirements for MPLS and GMPLS June 2007
Table of Contents
1. Introduction ....................................................2
2. Terminology .....................................................3
2.1. Conventions Used in This Document ..........................4
3. Motivations for PCE-Based Inter-Area Path Computation ...........4
4. Detailed Inter-Area Specific Requirements on PCECP ..............5
4.1. Control and Recording of Area Crossing .....................5
4.2. Area Recording .............................................6
4.3. Strict Explicit Path and Loose Path ........................6
4.4. PCE List Enforcement and Recording in Multiple-PCE
Computation ................................................6
4.5. Inclusion of Area IDs in Request ...........................7
4.6. Area Inclusion/Exclusion ...................................7
4.7. Inter-Area Diverse Path Computation ........................7
4.8. Inter-Area Policies ........................................8
4.9. Loop Avoidance .............................................8
5. Manageability Considerations ....................................9
6. Security Considerations .........................................9
7. Acknowledgments .................................................9
8. References ......................................................9
8.1. Normative References .......................................9
8.2. Informative References ....................................10
9. Contributors ...................................................10
1. Introduction
[RFC4105] lists a set of motivations and requirements for setting up
TE-LSPs across IGP area boundaries. These LSPs are called inter-area
TE-LSPs. These requirements include the computation of inter-area
shortest constrained paths with a key guideline being to respect the
IGP hierarchy concept, and particularly the containment of topology
information. The main challenge with inter-area MPLS-TE lies in path
computation. Indeed, the head-end LSR cannot compute an explicit
path across areas, as its topology visibility is limited to its own
area.
Inter-area path computation is one of the key applications of the
PCE-based architecture [RFC4655]. The computation of optimal inter-
area paths may be achieved using the services of one or more PCEs.
Such PCE-based inter-area path computation could rely for instance on
a single multi-area PCE that has the TE database of all the areas in
the IGP domain and can directly compute an end-to-end constrained
shortest path. Alternatively, this could rely on the cooperation
between PCEs whereby each PCE covers one or more IGP areas and the
full set of PCEs covers all areas.
Le Roux Informational [Page 2]
RFC 4927 PCECP Requirements for MPLS and GMPLS June 2007
The generic requirements for a PCE Communication Protocol (PCECP),
which allows a PCC to send path computation requests to a PCE and the
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