Segment Routing Architecture
RFC 8402

Document Type RFC - Proposed Standard (July 2018; No errata)
Last updated 2018-07-24
Replaces draft-filsfils-spring-segment-routing
Stream IETF
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Reviews
Stream WG state Submitted to IESG for Publication
Document shepherd Martin Vigoureux
Shepherd write-up Show (last changed 2017-02-21)
IESG IESG state RFC 8402 (Proposed Standard)
Consensus Boilerplate Yes
Telechat date
Responsible AD Alvaro Retana
Send notices to aretana.ietf@gmail.com
IANA IANA review state Version Changed - Review Needed
IANA action state No IANA Actions
Internet Engineering Task Force (IETF)                  C. Filsfils, Ed.
Request for Comments: 8402                               S. Previdi, Ed.
Category: Standards Track                                    L. Ginsberg
ISSN: 2070-1721                                      Cisco Systems, Inc.
                                                             B. Decraene
                                                            S. Litkowski
                                                                  Orange
                                                               R. Shakir
                                                            Google, Inc.
                                                               July 2018

                      Segment Routing Architecture

Abstract

   Segment Routing (SR) leverages the source routing paradigm.  A node
   steers a packet through an ordered list of instructions, called
   "segments".  A segment can represent any instruction, topological or
   service based.  A segment can have a semantic local to an SR node or
   global within an SR domain.  SR provides a mechanism that allows a
   flow to be restricted to a specific topological path, while
   maintaining per-flow state only at the ingress node(s) to the SR
   domain.

   SR can be directly applied to the MPLS architecture with no change to
   the forwarding plane.  A segment is encoded as an MPLS label.  An
   ordered list of segments is encoded as a stack of labels.  The
   segment to process is on the top of the stack.  Upon completion of a
   segment, the related label is popped from the stack.

   SR can be applied to the IPv6 architecture, with a new type of
   routing header.  A segment is encoded as an IPv6 address.  An ordered
   list of segments is encoded as an ordered list of IPv6 addresses in
   the routing header.  The active segment is indicated by the
   Destination Address (DA) of the packet.  The next active segment is
   indicated by a pointer in the new routing header.

Filsfils, et al.             Standards Track                    [Page 1]
RFC 8402                     Segment Routing                   July 2018

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/rfc8402.

Copyright Notice

   Copyright (c) 2018 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.

Filsfils, et al.             Standards Track                    [Page 2]
RFC 8402                     Segment Routing                   July 2018

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Link-State IGP Segments . . . . . . . . . . . . . . . . . . .   9
     3.1.  IGP-Prefix Segment (Prefix-SID) . . . . . . . . . . . . .   9
       3.1.1.  Prefix-SID Algorithm  . . . . . . . . . . . . . . . .   9
       3.1.2.  SR-MPLS . . . . . . . . . . . . . . . . . . . . . . .  10
       3.1.3.  SRv6  . . . . . . . . . . . . . . . . . . . . . . . .  12
     3.2.  IGP-Node Segment (Node-SID) . . . . . . . . . . . . . . .  13
     3.3.  IGP-Anycast Segment (Anycast-SID) . . . . . . . . . . . .  13
       3.3.1.  Anycast-SID in SR-MPLS  . . . . . . . . . . . . . . .  13
     3.4.  IGP-Adjacency Segment (Adj-SID) . . . . . . . . . . . . .  15
       3.4.1.  Parallel Adjacencies  . . . . . . . . . . . . . . . .  17
       3.4.2.  LAN Adjacency Segments  . . . . . . . . . . . . . . .  18
     3.5.  Inter-Area Considerations . . . . . . . . . . . . . . . .  18
   4.  BGP Segments  . . . . . . . . . . . . . . . . . . . . . . . .  19
     4.1.  BGP-Prefix Segment  . . . . . . . . . . . . . . . . . . .  19
     4.2.  BGP Peering Segments  . . . . . . . . . . . . . . . . . .  20
   5.  Binding Segment . . . . . . . . . . . . . . . . . . . . . . .  21
     5.1.  IGP Mirroring Context Segment . . . . . . . . . . . . . .  21
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