Segment Routing with MPLS data plane
draft-ietf-spring-segment-routing-mpls-18

Document Type Active Internet-Draft (spring WG)
Last updated 2018-12-10 (latest revision 2018-12-09)
Replaces draft-filsfils-spring-segment-routing-mpls
Stream IETF
Intended RFC status Proposed Standard
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Document shepherd Shraddha Hegde
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Network Working Group                                  A. Bashandy, Ed.
Internet Draft                                                   Arrcus
Intended status: Standards Track                       C. Filsfils, Ed.
Expires: June 2019                                          S. Previdi,
                                                    Cisco Systems, Inc.
                                                            B. Decraene
                                                           S. Litkowski
                                                                 Orange
                                                              R. Shakir
                                                                 Google
                                                       December 9, 2018

                   Segment Routing with MPLS data plane
                 draft-ietf-spring-segment-routing-mpls-18

Abstract

   Segment Routing (SR) leverages the source routing paradigm.  A node
   steers a packet through a controlled set of instructions, called
   segments, by prepending the packet with an SR header.  In the MPLS
   dataplane, the SR header is instantiated through a label stack. This
   document specifies the forwarding behavior to allow instantiating SR
   over the MPLS dataplane.

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
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   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 June 9, 2019.

Filsfils, et al.         Expires June 9, 2019                  [Page 1]
Internet-Draft        Segment Routing with MPLS           December 2018

Copyright Notice

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

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   described in the Simplified BSD License.

Table of Contents

   1. Introduction...................................................3
      1.1. Requirements Language.....................................4
   2. MPLS Instantiation of Segment Routing..........................4
      2.1. Multiple Forwarding Behaviors for the Same Prefix.........5
      2.2. SID Representation in the MPLS Forwarding Plane...........5
      2.3. Segment Routing Global Block and Local Block..............6
      2.4. Mapping a SID Index to an MPLS label......................6
      2.5. Incoming Label Collision..................................7
         2.5.1. Tie-breaking Rules..................................10
         2.5.2. Redistribution between Routing Protocol Instances...13
            2.5.2.1. Illustration...................................13
            2.5.2.2. Illustration 2.................................14
      2.6. Effect of Incoming Label Collision on Outgoing Label
      Programming...................................................14
      2.7. PUSH, CONTINUE, and NEXT.................................14
         2.7.1. PUSH................................................15
         2.7.2. CONTINUE............................................15
         2.7.3. NEXT................................................15
            2.7.3.1. Mirror SID.....................................15
      2.8. MPLS Label Downloaded to FIB for Global and Local SIDs...16
      2.9. Active Segment...........................................16
      2.10. Forwarding behavior for Global SIDs.....................16
         2.10.1. Forwarding for PUSH and CONTINUE of Global SIDs....16
         2.10.2. Forwarding for NEXT Operation for Global SIDs......18
      2.11. Forwarding Behavior for Local SIDs......................18
         2.11.1. Forwarding for PUSH Operation on Local SIDs........18
         2.11.2. Forwarding for CONTINUE Operation for Local SIDs...19
         2.11.3. Outgoing label for NEXT Operation for Local SIDs...19
   3. IANA Considerations...........................................19

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