IS-IS Extensions for Segment Routing
RFC 8667

Document Type RFC - Proposed Standard (December 2019; No errata)
Last updated 2019-12-06
Replaces draft-previdi-isis-segment-routing-extensions
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Stream WG state Submitted to IESG for Publication
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Shepherd write-up Show (last changed 2018-11-08)
IESG IESG state RFC 8667 (Proposed Standard)
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Send notices to "Christian Hopps" <chopps@chopps.org>, Uma Chunduri <uma.chunduri@huawei.com>, aretana.ietf@gmail.com
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Internet Engineering Task Force (IETF)                   S. Previdi, Ed.
Request for Comments: 8667                           Huawei Technologies
Category: Standards Track                               L. Ginsberg, Ed.
ISSN: 2070-1721                                              C. Filsfils
                                                     Cisco Systems, Inc.
                                                             A. Bashandy
                                                                  Arrcus
                                                              H. Gredler
                                                            RtBrick Inc.
                                                             B. Decraene
                                                                  Orange
                                                           December 2019

                  IS-IS Extensions for Segment Routing

Abstract

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

   This document describes the IS-IS extensions that need to be
   introduced for Segment Routing operating on an MPLS data plane.

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/rfc8667.

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.  Prefix Segment Identifier (Prefix-SID) Sub-TLV
       2.1.1.  Flags
       2.1.2.  Prefix-SID Propagation
     2.2.  Adjacency Segment Identifier
       2.2.1.  Adjacency Segment Identifier (Adj-SID) Sub-TLV
       2.2.2.  Adjacency Segment Identifier (LAN-Adj-SID) Sub-TLV
     2.3.  SID/Label Sub-TLV
     2.4.  SID/Label Binding TLV
       2.4.1.  Flags
       2.4.2.  Range
       2.4.3.  Prefix Length, Prefix
       2.4.4.  Mapping Server Prefix-SID
       2.4.5.  SID/Label Sub-TLV
       2.4.6.  Example Encodings
     2.5.  Multi-Topology SID/Label Binding TLV
   3.  Router Capabilities
     3.1.  SR-Capabilities Sub-TLV
     3.2.  SR-Algorithm Sub-TLV
     3.3.  SR Local Block Sub-TLV
     3.4.  SRMS Preference Sub-TLV
   4.  IANA Considerations
     4.1.  Sub-TLVs for Types 22, 23, 25, 141, 222, and 223
     4.2.  Sub-TLVs for Types 135, 235, 236, and 237
     4.3.  Sub-TLVs for Type 242
     4.4.  New TLV Codepoint and Sub-TLV Registry
   5.  Security Considerations
   6.  References
     6.1.  Normative References
     6.2.  Informative References
   Acknowledgements
   Contributors
   Authors' Addresses

1.  Introduction

   Segment Routing (SR) allows for a flexible definition of end-to-end
   paths within IGP topologies by encoding paths as sequences of
   topological sub-paths, 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 of the cases, is a one-hop path.  SR's
   control plane can be applied to both IPv6 and MPLS data planes and
   does not require any additional signaling (other than the regular
   IGP).  For example, when used in MPLS networks, SR paths do not
   require any LDP or RSVP-TE signaling.  Still, SR can interoperate in
   the presence of Label Switched Paths (LSPs) established with RSVP or
   LDP.

   There are additional segment types, e.g., the Binding SID as defined
   in [RFC8402].  This document also defines an advertisement for one
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