IP Fast Reroute Framework
RFC 5714
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RFC - Informational
(January 2010; No errata)
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2015-10-14
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IETF
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IESG state |
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RFC 5714 (Informational)
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Ross Callon
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Internet Engineering Task Force (IETF) M. Shand
Request for Comments: 5714 S. Bryant
Category: Informational Cisco Systems
ISSN: 2070-1721 January 2010
IP Fast Reroute Framework
Abstract
This document provides a framework for the development of IP fast-
reroute mechanisms that provide protection against link or router
failure by invoking locally determined repair paths. Unlike MPLS
fast-reroute, the mechanisms are applicable to a network employing
conventional IP routing and forwarding.
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.
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/rfc5714.
Copyright Notice
Copyright (c) 2010 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.
Shand & Bryant Informational [Page 1]
RFC 5714 IP Fast Reroute Framework January 2010
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Scope and Applicability . . . . . . . . . . . . . . . . . . . 5
4. Problem Analysis . . . . . . . . . . . . . . . . . . . . . . . 5
5. Mechanisms for IP Fast-Reroute . . . . . . . . . . . . . . . . 7
5.1. Mechanisms for Fast Failure Detection . . . . . . . . . . 7
5.2. Mechanisms for Repair Paths . . . . . . . . . . . . . . . 8
5.2.1. Scope of Repair Paths . . . . . . . . . . . . . . . . 9
5.2.2. Analysis of Repair Coverage . . . . . . . . . . . . . 9
5.2.3. Link or Node Repair . . . . . . . . . . . . . . . . . 10
5.2.4. Maintenance of Repair Paths . . . . . . . . . . . . . 10
5.2.5. Local Area Networks . . . . . . . . . . . . . . . . . 11
5.2.6. Multiple Failures and Shared Risk Link Groups . . . . 11
5.3. Mechanisms for Micro-Loop Prevention . . . . . . . . . . . 12
6. Management Considerations . . . . . . . . . . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 13
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
9. Informative References . . . . . . . . . . . . . . . . . . . . 14
1. Introduction
When a link or node failure occurs in a routed network, there is
inevitably a period of disruption to the delivery of traffic until
the network re-converges on the new topology. Packets for
destinations that were previously reached by traversing the failed
component may be dropped or may suffer looping. Traditionally, such
disruptions have lasted for periods of at least several seconds, and
most applications have been constructed to tolerate such a quality of
service.
Recent advances in routers have reduced this interval to under a
second for carefully configured networks using link state IGPs.
However, new Internet services are emerging that may be sensitive to
periods of traffic loss that are orders of magnitude shorter than
this.
Addressing these issues is difficult because the distributed nature
of the network imposes an intrinsic limit on the minimum convergence
time that can be achieved.
However, there is an alternative approach, which is to compute backup
routes that allow the failure to be repaired locally by the router(s)
detecting the failure without the immediate need to inform other
routers of the failure. In this case, the disruption time can be
limited to the small time taken to detect the adjacent failure and
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