Prefix Unreachable Announcement
draft-wang-lsr-prefix-unreachable-annoucement-01
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LSR Working Group A. Wang
Internet-Draft China Telecom
Intended status: Standards Track Z. Hu
Expires: June 11, 2020 Huawei Technologies
December 9, 2019
Prefix Unreachable Announcement
draft-wang-lsr-prefix-unreachable-annoucement-01
Abstract
This document describes the mechanism that can be used to announce
the unreachable prefixes for service fast convergence.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 11, 2020.
Copyright Notice
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
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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described in the Simplified BSD License.
Wang & Hu Expires June 11, 2020 [Page 1]
Internet-Draft PUA December 2019
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 2
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
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 6
10. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
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 June 11, 2020 [Page 2]
Internet-Draft PUA December 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
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