Signaling MSD (Maximum SID Depth) using Border Gateway Protocol - Link State
draft-ietf-idr-bgp-ls-segment-routing-msd-18

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Last updated 2020-08-03 (latest revision 2020-05-08)
Replaces draft-tantsura-idr-bgp-ls-segment-routing-msd
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Details
IDR Working Group                                            J. Tantsura
Internet-Draft                                              Apstra, Inc.
Intended status: Standards Track                             U. Chunduri
Expires: November 9, 2020                         Futurewei Technologies
                                                           K. Talaulikar
                                                           Cisco Systems
                                                               G. Mirsky
                                                               ZTE Corp.
                                                        N. Triantafillis
                                                     Amazon Web Services
                                                             May 8, 2020

 Signaling MSD (Maximum SID Depth) using Border Gateway Protocol - Link
                                 State
              draft-ietf-idr-bgp-ls-segment-routing-msd-18

Abstract

   This document defines a way for a Border Gateway Protocol - Link
   State (BGP-LS) speaker 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 Identifier (SID) stack can be
   supported in a given network.

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
   working documents as Internet-Drafts.  The list of current Internet-
   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 November 9, 2020.

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Copyright Notice

   Copyright (c) 2020 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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   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.  Conventions used in this document . . . . . . . . . . . .   3
       1.1.1.  Terminology . . . . . . . . . . . . . . . . . . . . .   3
       1.1.2.  Requirements Language . . . . . . . . . . . . . . . .   4
   2.  Advertisement of MSD via BGP-LS . . . . . . . . . . . . . . .   4
   3.  Node MSD TLV  . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Link MSD TLV  . . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Manageability Considerations  . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   7
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   8
     10.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   When Segment Routing (SR) [RFC8402] 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 on a
   given SR path.  This ensures that the Segment Identifier (SID) stack
   depth of a computed path doesn't exceed the number of SIDs the node
   is capable of imposing.

   [RFC8664] defines how to signal MSD in the Path Computation Element
   Protocol (PCEP).  The OSPF and IS-IS extensions for signaling of MSD
   are defined in [RFC8476] and [RFC8491] respectively.

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   However, if PCEP is not supported/configured on the head-end of a SR
   tunnel or a Binding-SID anchor node, and the controller does not
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