Definition of a Record Route Object (RRO) Node-Id Sub-Object
RFC 4561

• Status
• IESG evaluation record
• IESG writeups
• Email expansions
• History

• Versions
• 07

Network Working Group                                 J.-P. Vasseur, Ed.
Request for Comments: 4561                                        Z. Ali
Category: Standards Track                                   S. Sivabalan
                                                     Cisco Systems, Inc.
                                                               June 2006

     Definition of a Record Route Object (RRO) Node-Id Sub-Object

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   In the context of MPLS TE Fast Reroute, the Merge Point (MP) address
   is required at the Point of Local Repair (PLR) in order to select a
   backup tunnel intersecting a fast reroutable Traffic Engineering
   Label Switched Path (TE LSP) on a downstream Label Switching Router
   (LSR).  However, existing protocol mechanisms are not sufficient to
   find an MP address in multi-domain routing networks where a domain is
   defined as an Interior Gateway Protocol (IGP) area or an Autonomous
   System (AS).  Hence, the current MPLS Fast Reroute mechanism cannot
   be used in order to protect inter-domain TE LSPs from a failure of an
   Area Border Router (ABR) or Autonomous System Border Router (ASBR).
   This document specifies the use of existing Record Route Object (RRO)
   IPv4 and IPv6 sub-objects (with a new flag defined) thus defining the
   node-id sub-object in order to solve this issue.  The MPLS Fast
   Reroute mechanism mentioned in this document refers to the "Facility
   backup" MPLS TE Fast Reroute method.

Vasseur, et al.             Standards Track                     [Page 1]
RFC 4561          Definition of RRO Node-Id Sub-Object         June 2006

Table of Contents

   1. Introduction ....................................................2
   2. Terminology .....................................................4
      2.1. Conventions Used in This Document ..........................5
   3. Signaling Node-Ids in RROs ......................................5
   4. Finding Merge Point .............................................6
   5. Security Considerations .........................................7
   6. Acknowledgements ................................................7
   7. References ......................................................7
      7.1. Normative References .......................................7
      7.2. Informative References .....................................8

1.  Introduction

   MPLS Fast Reroute (FRR) [FAST-REROUTE] is a fast recovery local
   protection technique used to protect Traffic Engineering LSPs from
   link/node/Shared Risk Link Group (SRLG) failure.  One or more backup
   tunnels are pre-established to protect against the failure of a
   link/node/SRLG.  In case of failure, every protected TE LSP
   traversing the failed resource is rerouted onto the appropriate
   backup tunnel.

   There are several requirements on the backup tunnel path that must be
   satisfied.  First, the backup tunnel must not traverse the element
   that it protects.  In addition, a primary tunnel and its associated
   backup tunnel should intersect at least at two points (nodes): Point
   of Local Repair (PLR) and Merge Point (MP).  The former is the head-
   end LSR of the backup tunnel, and the latter is the tail-end LSR of
   the backup tunnel.  The PLR is where FRR is triggered when
   link/node/SRLG failure happens.

   There are different methods for computing paths for backup tunnels at
   a given PLR.  Specifically, a user can statically configure one or
   more backup tunnels at the PLR with an explicitly configured path, or
   the PLR can be configured to automatically compute a backup path or
   to send a path computation request to a PCE (see [PCE-ARCH]).

   Consider the following scenario (Figure 1).

   Assumptions:

   - A multi-area network made of three areas: 0, 1, and 2.

   - A fast reroutable TE LSP T1 (TE LSP signaled with the "Local
     Protection Desired" bit set in the SESSION-ATTRIBUTE object or the
     FAST-REROUTE object) from R0 to R3.

Vasseur, et al.             Standards Track                     [Page 2]
RFC 4561          Definition of RRO Node-Id Sub-Object         June 2006

   - A backup tunnel B1 from R1 to R2, not traversing ABR1, and
     following the R1-ABR3-R2 path.

   - The PLR R1 reroutes any protected TE LSP traversing ABR1 onto the
     backup tunnel B1 in case of ABR1's failure.

             <--- area 1 --><---area 0---><---area 2--->
                R0-----R1-ABR1--R2------ABR2--------R3
                       \        /
                        \      /