Definition of a Record Route Object (RRO) Node-Id Sub-Object
RFC 4561
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RFC - Proposed Standard
(June 2006; No errata)
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2015-10-14
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RFC 4561 (Proposed Standard)
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Alex Zinin
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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
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