Prefix Unreachable Announcement
draft-wang-lsr-prefix-unreachable-annoucement-03

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LSR Working Group                                                A. Wang
Internet-Draft                                             China Telecom
Intended status: Standards Track                                   Z. Hu
Expires: January 28, 2021                                        Y. Xiao
                                                     Huawei Technologies
                                                           July 27, 2020

                    Prefix Unreachable Announcement
            draft-wang-lsr-prefix-unreachable-annoucement-03

Abstract

   This document describes the mechanism that can be used to announce
   the unreachable prefixes for service fast convergence.

Status of This Memo

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   This Internet-Draft will expire on January 28, 2021.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Wang, et al.            Expires January 28, 2021                [Page 1]
Internet-Draft                     PUA                         July 2020

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  Scenario Description  . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Inter-Area Node Failure Scenario  . . . . . . . . . . . .   3
     3.2.  Inter-Area Links Failure Scenario . . . . . . . . . . . .   3
     3.3.  Intra-Area Node Failure Scenario  . . . . . . . . . . . .   4
   4.  Inter-area prefix unreachable solution  . . . . . . . . . . .   4
   5.  Intra-area prefix unreachable solution  . . . . . . . . . . .   5
   6.  Implementation Consideration  . . . . . . . . . . . . . . . .   5
     6.1.  Usages of Tunnel among ABRs . . . . . . . . . . . . . . .   6
     6.2.  Fast Rerouting to Avoid Routing Backhole  . . . . . . . .   7
     6.3.  PUA Capabilities Announcement . . . . . . . . . . . . . .   8
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   9.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .   9
   10. Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   OSPF and IS-IS have the summary route and default route mechanism on
   area border router or L1L2 border router, which is used to increase
   the scalability of these IGP protocols.  Such summary mechanism can
   also reduce the SPF calculation time when the link oscillation occurs
   in another area.

   The summary route and the default route may cover the host route or
   link prefixes of intra area or inter area.  But in some situations,
   the router needs to know the exact reachability information about
   prefix in other area, especially when the prefix is unreachable but
   it is located within the summary range.

   With the introduction of SRv6, more and more services are migrated
   from the MPLS data plane to the IPv6 data plane.  The biggest
   difference between IPv6 and MPLS is that IPv6 has aggregation
   ability, so we need to reconsider how to know the prefix reachability
   in the case of aggregation.

   This document introduces the mechanism that can be used in such
   situation, to announce the unreachable prefixes which are located in
   the summary address range.

Wang, et al.            Expires January 28, 2021                [Page 2]
Internet-Draft                     PUA                         July 2020

2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119] .