Signaling MSD (Maximum SID Depth) using OSPF
draft-ietf-ospf-segment-routing-msd-10

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Last updated 2018-04-05
Replaces draft-tantsura-ospf-segment-routing-msd
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OSPF Working Group                                           J. Tantsura
Internet-Draft                                            Nuage Networks
Intended status: Standards Track                             U. Chunduri
Expires: October 7, 2018                             Huawei Technologies
                                                               S. Aldrin
                                                             Google, Inc
                                                               P. Psenak
                                                           Cisco Systems
                                                          April 05, 2018

              Signaling MSD (Maximum SID Depth) using OSPF
                 draft-ietf-ospf-segment-routing-msd-10

Abstract

   This document defines a way for an OSPF 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 maximum label imposition, but defines an encoding which can
   support other MSD types.  Here the term OSPF means both OSPFv2 and
   OSPFv3.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on October 7, 2018.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Tantsura, et al.         Expires October 7, 2018                [Page 1]
Internet-Draft                                                April 2018

   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
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   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
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Node MSD TLV  . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Link MSD sub-TLV  . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Using Node and Link MSD Advertisements  . . . . . . . . . . .   5
   6.  Base MPLS Imposition MSD  . . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   9.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   7
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     11.2.  Informative References . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

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 a given SR path to
   insure that the SID stack depth of a computed path doesn't exceed the
   number of SIDs the node is capable of imposing.

   The PCEP SR extensions draft [I-D.ietf-pce-segment-routing] signals
   MSD in SR PCE Capability TLV and METRIC Object.  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 which has
   been configured.  BGP-LS [RFC7752] defines a way to expose topology
   and associated attributes and capabilities of the nodes in that
   topology to a centralized controller.  MSD signaling by BGP-LS has
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