Signaling MSD (Maximum SID Depth) using IS-IS
draft-ietf-isis-segment-routing-msd-17
IS-IS Working Group J. Tantsura
Internet-Draft Nuage Networks
Intended status: Standards Track U. Chunduri
Expires: March 30, 2019 Huawei Technologies
S. Aldrin
Google, Inc
L. Ginsberg
Cisco Systems
September 26, 2018
Signaling MSD (Maximum SID Depth) using IS-IS
draft-ietf-isis-segment-routing-msd-17
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 SID stack can be supported in a given
network. This document only defines one type of MSD (Base MPLS
Imposition), but defines an encoding that can support other MSD
types. This document focuses on MSD use in a Segment Routing enabled
network, but MSD may also be useful when Segment Routing is not
enabled.
Status of This Memo
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This Internet-Draft will expire on March 30, 2019.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 4
3. Link MSD Advertisement . . . . . . . . . . . . . . . . . . . 5
4. Procedures for using Node and Link MSD Advertisements . . . . 6
5. Base MPLS Imposition MSD . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . 8
10.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
When Segment Routing (SR) paths are computed by a centralized
controller, it is critical that the controller learns the Maximum SID
Depth (MSD) that can be imposed at each node/link of a given SR path
to ensure that the Segment Identifier (SID) stack depth of a computed
path does not exceed the number of SIDs the node is capable of
imposing.
[I-D.ietf-pce-segment-routing] defines how to signal MSD in the Path
Computation Element Protocol (PCEP). However, if PCEP is not
supported/configured on the head-end of an SR tunnel or a Binding-SID
anchor node and controller does not participate in IGP routing, it
has no way to learn the MSD of nodes and links. BGP-LS (Distribution
of Link-State and TE Information using Border Gateway Protocol)
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