RFC 3785 (rfc3785) - Page 1 of 8

Use of Interior Gateway Protocol (IGP) Metric as a second MPLS Traffic Engineering (TE) Metric

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Network Working Group                                     F. Le Faucheur
Request for Comments: 3785                                     R. Uppili
BCP: 87                                              Cisco Systems, Inc.
Category: Best Current Practice                              A. Vedrenne
                                                               P. Merckx
                                                                  Equant
                                                              T. Telkamp
                                                         Global Crossing
                                                                May 2004


             Use of Interior Gateway Protocol (IGP) Metric
           as a second MPLS Traffic Engineering (TE) Metric

Status of this Memo

   This document specifies an Internet Best Current Practices for the
   Internet Community, and requests discussion and suggestions for
   improvements.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2004).  All Rights Reserved.

Abstract

   This document describes a common practice on how the existing metric
   of Interior Gateway Protocols (IGP) can be used as an alternative
   metric to the Traffic Engineering (TE) metric for Constraint Based
   Routing of MultiProtocol Label Switching (MPLS) Traffic Engineering
   tunnels.  This effectively results in the ability to perform
   Constraint Based Routing with optimization of one metric (e.g., link
   bandwidth) for some Traffic Engineering tunnels (e.g., Data Trunks)
   while optimizing another metric (e.g., propagation delay) for some
   other tunnels with different requirements (e.g., Voice Trunks).  No
   protocol extensions or modifications are required.  This text
   documents current router implementations and deployment practices.

1.  Introduction

   Interior Gateway Protocol (IGP) routing protocols (OSPF and IS-IS) as
   well as MultiProtocol Label Switching (MPLS) signaling protocols
   (RSVP-TE and CR-LDP) have been extended (as specified in [ISIS-TE],
   [OSPF-TE], [RSVP-TE] and [CR-LDP]) in order to support the Traffic
   Engineering (TE) functionality as defined in [TE-REQ].






Le Faucheur, et al.      Best Current Practice
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