OSPF Extensions for Segment Routing
RFC 8665

Document Type RFC - Proposed Standard (December 2019; No errata)
Authors Peter Psenak  , Stefano Previdi  , Clarence Filsfils  , Hannes Gredler  , Rob Shakir  , Wim Henderickx  , Jeff Tantsura 
Last updated 2019-12-06
Replaces draft-psenak-ospf-segment-routing-extensions
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Stream WG state Submitted to IESG for Publication
Document shepherd Acee Lindem
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Send notices to "Acee Lindem" <acee@cisco.com>, aretana.ietf@gmail.com
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Internet Engineering Task Force (IETF)                    P. Psenak, Ed.
Request for Comments: 8665                               S. Previdi, Ed.
Category: Standards Track                                    C. Filsfils
ISSN: 2070-1721                                      Cisco Systems, Inc.
                                                              H. Gredler
                                                            RtBrick Inc.
                                                               R. Shakir
                                                            Google, Inc.
                                                           W. Henderickx
                                                                   Nokia
                                                             J. Tantsura
                                                            Apstra, Inc.
                                                           December 2019

                  OSPF Extensions for Segment Routing

Abstract

   Segment Routing (SR) allows a flexible definition of end-to-end paths
   within IGP topologies by encoding paths as sequences of topological
   subpaths called "segments".  These segments are advertised by the
   link-state routing protocols (IS-IS and OSPF).

   This document describes the OSPFv2 extensions required for Segment
   Routing.

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/rfc8665.

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.

Table of Contents

   1.  Introduction
     1.1.  Requirements Language
   2.  Segment Routing Identifiers
     2.1.  SID/Label Sub-TLV
   3.  Segment Routing Capabilities
     3.1.  SR-Algorithm TLV
     3.2.  SID/Label Range TLV
     3.3.  SR Local Block TLV
     3.4.  SRMS Preference TLV
   4.  OSPF Extended Prefix Range TLV
   5.  Prefix-SID Sub-TLV
   6.  Adjacency Segment Identifier (Adj-SID)
     6.1.  Adj-SID Sub-TLV
     6.2.  LAN Adj-SID Sub-TLV
   7.  Elements of Procedure
     7.1.  Intra-area Segment Routing in OSPFv2
     7.2.  Inter-area Segment Routing in OSPFv2
     7.3.  Segment Routing for External Prefixes
     7.4.  Advertisement of Adj-SID
       7.4.1.  Advertisement of Adj-SID on Point-to-Point Links
       7.4.2.  Adjacency SID on Broadcast or NBMA Interfaces
   8.  IANA Considerations
     8.1.  OSPF Router Information (RI) TLVs Registry
     8.2.  OSPFv2 Extended Prefix Opaque LSA TLVs Registry
     8.3.  OSPFv2 Extended Prefix TLV Sub-TLVs Registry
     8.4.  OSPFv2 Extended Link TLV Sub-TLVs Registry
     8.5.  IGP Algorithm Types Registry
   9.  TLV/Sub-TLV Error Handling
   10. Security Considerations
   11. References
     11.1.  Normative References
     11.2.  Informative References
   Acknowledgements
   Contributors
   Authors' Addresses

1.  Introduction

   Segment Routing (SR) allows a flexible definition of end-to-end paths
   within IGP topologies by encoding paths as sequences of topological
   subpaths called "segments".  These segments are advertised by the
   link-state routing protocols (IS-IS and OSPF).  Prefix segments
   represent an ECMP-aware shortest path to a prefix (or a node), as per
   the state of the IGP topology.  Adjacency segments represent a hop
   over a specific adjacency between two nodes in the IGP.  A prefix
   segment is typically a multi-hop path while an adjacency segment, in
   most cases, is a one-hop path.  SR's control plane can be applied to
   both IPv6 and MPLS data planes, and it does not require any
   additional signaling (other than IGP extensions).  The IPv6 data
   plane is out of the scope of this specification; it is not applicable
   to OSPFv2, which only supports the IPv4 address family.  When used in
   MPLS networks, SR paths do not require any LDP or RSVP-TE signaling.
   However, SR can interoperate in the presence of LSPs established with
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