Segment Routing Candidate Path Hot-standby switch in BGP
draft-yang-idr-sr-candidate-path-switch-00

Document Type Active Internet-Draft (individual)
Authors Liping Yang  , Hao Li  , Yang Wang  , Yuanxiang Qiu  , Mengxiao Chen 
Last updated 2021-02-02
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Inter-Domain Routing Working Group                            L. Yang
Internet-Draft                                                  H. Li
Intended status: Standards Track                              Y. Wang
Expires: August 2, 2021                                        Y. Qiu
                                                              M. Chen
                                                     H3C Technologies
                                                     February 2, 2021

        Segment Routing Candidate Path Hot-standby switch in BGP
              draft-yang-idr-sr-candidate-path-switch-00

Abstract

   Segment Routing is a source routing paradigm that explicitly 
   indicates the forwarding path for packets at the ingress node.  An SR 
   policy is a set of candidate SR paths consisting of one or more 
   segment lists with necessary path attributes. If an SR policy has 
   multiple valid candidate paths, the device chooses the candidate path
   with the greatest preference value. If the chosen path fails, the SR 
   policy must select another candidate path. During path reselection, 
   packet loss might occur and thus affect service continuity. Therefore 
   the candidate path hot-standby function occurs, the headend can 
   compute two candidate paths, one is master and the other is backup, 
   set them to the forwarding plane, and in this way, the switchover
   time is reduced.
   
   This document defines extensions to BGP to distribute hot-standby 
   switch within SR policies.

Status of This Memo

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   This Internet-Draft will expire on June 1, 2021.

   
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   This document is subject to BCP 78 and the IETF Trust's Legal 
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   3.  SR Policy for Hot-standby  . . . . . . . . . .. . . . . . . .   3
     3.1.  Path Hot-standby Sub-TLV  . . . . . . . . . . . . . . . . . 4
   4.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Implementation Status . . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . .    7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
      9.1.  Normative References . . . . . . . . . . . . . . . . . .   7
      9.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1. Introduction

   Segment routing (SR) [RFC8402] is a source routing paradigm that 
   explicitly indicates the forwarding path for packets at the ingress
   node.  The ingress node steers packets into a specific path 
   according to the Segment Routing Policy (SR Policy) as defined in
   [I-D.ietf-spring-segment-routing-policy].  In order to distribute SR
   policies to the headend, [I-D.ietf-idr-segment-routing-te-policy] 
   specifies a mechanism by using BGP.
 
 
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   An SR Policy includes multiple candidate paths, of which at any time
   there is only one active candidate path that is provisioned in the 
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