Preferred Path Loop-Free Alternate (pLFA)
draft-bryant-rtgwg-plfa-00

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Routing Area Working Group                                     S. Bryant
Internet-Draft                                               U. Chunduri
Intended status: Informational                                 T. Eckert
Expires: January 3, 2020                      Futurewei Technologies Inc
                                                           July 02, 2019

               Preferred Path Loop-Free Alternate (pLFA)
                       draft-bryant-rtgwg-plfa-00

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.

Status of This Memo

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   This Internet-Draft will expire on January 3, 2020.

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   Copyright (c) 2019 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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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents

Bryant, et al.           Expires January 3, 2020                [Page 1]
Internet-Draft                    pLFA                         July 2019

   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.

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

1.  Introduction

   Preferred Path Routing (PPR)