Internet Engineering Task Force (IETF) C. Filsfils, Ed.
Request for Comments: 6571 Cisco Systems
Category: Informational P. Francois, Ed.
ISSN: 2070-1721 Institute IMDEA Networks
M. Shand
B. Decraene
France Telecom
J. Uttaro
AT&T
N. Leymann
M. Horneffer
Deutsche Telekom
June 2012
Loop-Free Alternate (LFA) Applicability
in Service Provider (SP) Networks
Abstract
In this document, we analyze the applicability of the Loop-Free
Alternate (LFA) method of providing IP fast reroute in both the core
and access parts of Service Provider networks. We consider both the
link and node failure cases, and provide guidance on the
applicability of LFAs to different network topologies, with special
emphasis on the access parts of the network.
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/rfc6571.
Filsfils, et al. Informational [Page 1]RFC 6571 LFA Applicability in SP Networks June 2012Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
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Table of Contents
1. Introduction ....................................................3
2. Terminology .....................................................4
3. Access Network ..................................................6
3.1. Triangle ...................................................8
3.1.1. E1C1 Failure ........................................8
3.1.2. C1E1 Failure ........................................9
3.1.3. uLoop ...............................................9
3.1.4. Conclusion .........................................10
3.2. Full Mesh .................................................10
3.2.1. E1A1 Failure .......................................10
3.2.2. A1E1 Failure .......................................11
3.2.3. A1C1 Failure .......................................11
3.2.4. C1A1 Failure .......................................12
3.2.5. uLoop ..............................................12
3.2.6. Conclusion .........................................12
3.3. Square ....................................................13
3.3.1. E1A1 Failure .......................................13
3.3.2. A1E1 Failure .......................................14
3.3.3. A1C1 Failure .......................................15
3.3.4. C1A1 Failure .......................................15
3.3.5. Conclusion .........................................17
3.3.6. A Square Might Become a Full Mesh ..................17
3.3.7. A Full Mesh Might Be More Economical Than a
Square .............................................17
3.4. Extended U ................................................18
3.4.1. E1A1 Failure .......................................19
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