Signaling Maximum SID Depth (MSD) Using IS-IS
RFC 8491
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Type |
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RFC - Proposed Standard
(November 2018; No errata)
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Last updated |
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2018-11-14
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Replaces |
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draft-tantsura-isis-segment-routing-msd
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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
(wg milestones:
Jul 2018 - IS-IS Reverse Metric...,
Jul 2018 - IS-IS Segment Routin...
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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 2018-06-16)
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| IESG |
IESG state |
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RFC 8491 (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) J. Tantsura
Request for Comments: 8491 Apstra, Inc.
Category: Standards Track U. Chunduri
ISSN: 2070-1721 Huawei Technologies
S. Aldrin
Google, Inc.
L. Ginsberg
Cisco Systems
November 2018
Signaling Maximum SID Depth (MSD) Using IS-IS
Abstract
This document defines a way for an Intermediate System to
Intermediate System (IS-IS) router to advertise multiple types of
supported Maximum SID Depths (MSDs) at node and/or link granularity.
Such advertisements allow entities (e.g., centralized controllers) to
determine whether a particular Segment ID (SID) stack can be
supported in a given network. This document only defines one type of
MSD: Base MPLS Imposition. However, it defines an encoding that can
support other MSD types. This document focuses on MSD use in a
network that is Segment Routing (SR) enabled, but MSD may also be
useful when SR is not enabled.
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/rfc8491.
Tantsura, et al. Standards Track [Page 1]
RFC 8491 Signaling MSD Using IS-IS November 2018
Copyright Notice
Copyright (c) 2018 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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 4
3. Link MSD Advertisement . . . . . . . . . . . . . . . . . . . 5
4. Procedures for Defining and Using Node and Link MSD
Advertisements . . . . . . . . . . . . . . . . . . . . . . . 6
5. Base MPLS Imposition MSD . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . 9
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 10
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
When Segment Routing (SR) paths are computed by a centralized
controller, it is critical that the controller learn the Maximum SID
Depth (MSD) that can be imposed at each node/link of a given SR path.
This ensures that the Segment Identifier (SID) stack depth of a
computed path does not exceed the number of SIDs the node is capable
of imposing.
[PCEP-EXT] defines how to signal MSD in the Path Computation Element
Communication Protocol (PCEP). However, if PCEP is not supported/
configured on the head-end of an SR tunnel or a Binding-SID anchor
node, and the controller does not participate in IGP routing, it has
no way of learning the MSD of nodes and links. BGP-LS (Distribution
Tantsura, et al. Standards Track [Page 2]
RFC 8491 Signaling MSD Using IS-IS November 2018
of Link-State and TE Information Using Border Gateway Protocol)
[RFC7752] defines a way to expose topology and associated attributes
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