IS-IS Routing with Reverse Metric
RFC 8500
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Type |
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RFC - Proposed Standard
(February 2019; No errata)
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Last updated |
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2019-02-28
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Replaces |
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draft-amante-isis-reverse-metric
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Stream |
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IETF
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plain text
pdf
html
bibtex
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Reviews |
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WG state
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Submitted to IESG for Publication
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Document shepherd |
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Christian Hopps
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Shepherd write-up |
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Show
(last changed 2018-07-06)
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| IESG |
IESG state |
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RFC 8500 (Proposed Standard)
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Consensus Boilerplate |
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Yes
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Telechat date |
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Responsible AD |
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Alvaro Retana
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Send notices to |
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Christian Hopps <chopps@chopps.org>, aretana.ietf@gmail.com
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| IANA |
IANA review state |
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IANA OK - Actions Needed
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IANA action state |
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RFC-Ed-Ack
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Internet Engineering Task Force (IETF) N. Shen
Request for Comments: 8500 Cisco Systems
Category: Standards Track S. Amante
ISSN: 2070-1721 Apple Inc.
M. Abrahamsson
T-Systems Nordic
February 2019
IS-IS Routing with Reverse Metric
Abstract
This document describes a mechanism to allow IS-IS routing to quickly
and accurately shift traffic away from either a point-to-point or
multi-access LAN interface during network maintenance or other
operational events. This is accomplished by signaling adjacent IS-IS
neighbors with a higher reverse metric, i.e., the metric towards the
signaling IS-IS router.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8500.
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
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.
Shen, et al. Standards Track [Page 1]
RFC 8500 IS-IS Reverse Metric February 2019
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Node and Link Isolation . . . . . . . . . . . . . . . . . 2
1.2. Distributed Forwarding Planes . . . . . . . . . . . . . . 3
1.3. Spine-Leaf Applications . . . . . . . . . . . . . . . . . 3
1.4. LDP IGP Synchronization . . . . . . . . . . . . . . . . . 3
1.5. IS-IS Reverse Metric . . . . . . . . . . . . . . . . . . 3
1.6. Specification of Requirements . . . . . . . . . . . . . . 4
2. IS-IS Reverse Metric TLV . . . . . . . . . . . . . . . . . . 4
3. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 6
3.1. Processing Changes to Default Metric . . . . . . . . . . 6
3.2. Multi-Topology IS-IS Support on Point-to-Point Links . . 7
3.3. Multi-access LAN Procedures . . . . . . . . . . . . . . . 7
3.4. LDP/IGP Synchronization on LANs . . . . . . . . . . . . . 8
3.5. Operational Guidelines . . . . . . . . . . . . . . . . . 9
4. Security Considerations . . . . . . . . . . . . . . . . . . . 10
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1. Normative References . . . . . . . . . . . . . . . . . . 10
6.2. Informative References . . . . . . . . . . . . . . . . . 11
Appendix A. Node Isolation Challenges . . . . . . . . . . . . . 13
Appendix B. Link Isolation Challenges . . . . . . . . . . . . . 13
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 15
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
The IS-IS [ISO10589] routing protocol has been widely used in
Internet Service Provider IP/MPLS networks. Operational experience
with the protocol combined with ever increasing requirements for
lossless operations have demonstrated some operational issues. This
document describes the issues and a mechanism for mitigating them.
This document defines the IS-IS "Reverse Metric" mechanism that
allows an IS-IS node to send a Reverse Metric TLV through the IS-IS
Hello (IIH) PDU to the neighbor or pseudonode to adjust the routing
metric on the inbound direction.
1.1. Node and Link Isolation
The IS-IS routing mechanism has the overload bit, which can be used
by operators to perform disruptive maintenance on the router. But in
many operational maintenance cases, it is not necessary to divert all
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