Prefix Unreachable Announcement for SRv6 Fast Convergence
draft-wang-lsr-prefix-unreachable-annoucement-00

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LSR Working Group                                                A. Wang
Internet-Draft                                             China Telecom
Intended status: Standards Track                                   Z. Hu
Expires: April 26, 2020                              Huawei Technologies
                                                        October 24, 2019

       Prefix Unreachable Announcement for SRv6 Fast Convergence
            draft-wang-lsr-prefix-unreachable-annoucement-00

Abstract

   This document describes the mechanism that can be used to announce
   the unreachable prefixes for SRv6 fast convergence.

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   This Internet-Draft will expire on April 26, 2020.

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   Copyright (c) 2019 IETF Trust and the persons identified as the
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Wang & Hu                Expires April 26, 2020                 [Page 1]
Internet-Draft                     PUA                      October 2019

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   2
   3.  Scenario Description  . . . . . . . . . . . . . . . . . . . .   3
   4.  Inter-area prefix unreachable solution  . . . . . . . . . . .   3
   5.  Intra-area prefix unreachable solution  . . . . . . . . . . .   4
   6.  Implementation Consideration  . . . . . . . . . . . . . . . .   4
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   9.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .   5
   10. Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   OSPF and IS-IS have the summary route and default route mechanism on
   area border router or L1L2 border router, which can be 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.

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] .

Wang & Hu                Expires April 26, 2020                 [Page 2]
Internet-Draft                     PUA                      October 2019

3.  Scenario Description

   Figure1 illustrates the topology scenario when OSPF is running in
   multi-area.  R0-R4 are routers in backbone area, S1-S4,T1-T4 are
   internal routers in area 1 and area 2 respectively.  R1 and R3 are
   area border routers between area 0 and area 1.  R2 and R4 are area
   border routers between area 0 and area 2.  Ps2 is the host address of
   S2 and Pt2 is the host address T2.

    +---------------------+------+--------+-----+--------------+
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