Preferred Path Loop-Free Alternate (pLFA)
draft-bryant-rtgwg-plfa-01

Document Type Active Internet-Draft (individual)
Authors Stewart Bryant  , Uma Chunduri  , Toerless Eckert 
Last updated 2020-12-22
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Routing Area Working Group                                     S. Bryant
Internet-Draft                                                 S. Bryant
Intended status: Informational                               U. Chunduri
Expires: June 25, 2021                                         T. Eckert
                                              Futurewei Technologies Inc
                                                       December 22, 2020

               Preferred Path Loop-Free Alternate (pLFA)
                       draft-bryant-rtgwg-plfa-01

Abstract

   Fast re-route (FRR) is a technique that allows productive forwarding
   to continue in a network after a failure has occurred, but before the
   network has has time to re-converge.  This is achieved by forwarding
   a packet on an alternate path that will not result in the packet
   looping.  Preferred Path Routing (PPR) provides a method of injecting
   explicit paths into the routing protocol.  The use of PPR to support
   FRR has a number of advantages.  This document describes the
   advantages of using PPR to provide a loop-free alternate FRR path,
   and provides a framework for its use in this application.

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   Copyright (c) 2020 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
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   (https://trustee.ietf.org/license-info) in effect on the date of

Bryant, et al.            Expires June 25, 2021                 [Page 1]
Internet-Draft                    pLFA                     December 2020

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  A Note on the term IPFRR  . . . . . . . . . . . . . . . .   3
   2.  PPR Overview  . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Preferred Path LFA (pLFA) Deployment Advantages . . . . . . .   4
   4.  Simple Repair Using pLFA  . . . . . . . . . . . . . . . . . .   6
     4.1.  Link Repair . . . . . . . . . . . . . . . . . . . . . . .   6
     4.2.  Node Repair . . . . . . . . . . . . . . . . . . . . . . .   7
     4.3.  Shared Risk Link Groups . . . . . . . . . . . . . . . . .   8
     4.4.  Local Area Networks . . . . . . . . . . . . . . . . . . .   9
     4.5.  Multiple Independent Failures . . . . . . . . . . . . . .   9
     4.6.  Multi-homed Prefixes  . . . . . . . . . . . . . . . . . .   9
     4.7.  ECMP  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   5.  Repair To A Traffic Engineered Alternate Path . . . . . . . .  10
   6.  Use of a Repair Graph . . . . . . . . . . . . . . . . . . . .  11
     6.1.  Single Repair Graph . . . . . . . . . . . . . . . . . . .  11
     6.2.  Multiple Disjoint Graphs  . . . . . . . . . . . . . . . .  11
   7.  Centralized and Decentralized Approaches  . . . . . . . . . .  13
   8.  Independence of operation . . . . . . . . . . . . . . . . . .  14
   9.  Data-plane Considerations . . . . . . . . . . . . . . . . . .  14
     9.1.  Traditional IP  . . . . . . . . . . . . . . . . . . . . .  15
     9.2.  Segment Routing over an IPv6 Data Plane (SRv6)  . . . . .  15
     9.3.  MPLS  . . . . . . . . . . . . . . . . . . . . . . . . . .  15
   10. Loop Free Convergence . . . . . . . . . . . . . . . . . . . .  16
   11. OAM Considerations  . . . . . . . . . . . . . . . . . . . . .  16
   12. Privacy Considerations  . . . . . . . . . . . . . . . . . . .  16
   13. Security Considerations . . . . . . . . . . . . . . . . . . .  17
   14. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
   15. References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     15.1.  Normative References . . . . . . . . . . . . . . . . . .  17
     15.2.  Informative References . . . . . . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19
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