Segment Routing with MPLS data plane
draft-ietf-spring-segment-routing-mpls-13

Document Type Active Internet-Draft (spring WG)
Last updated 2018-04-02
Replaces draft-filsfils-spring-segment-routing-mpls
Stream IETF
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Network Working Group                                  A. Bashandy, Ed.
Internet Draft                                         C. Filsfils, Ed.
Intended status: Standards Track                            S. Previdi,
Expires: October 2018                               Cisco Systems, Inc.
                                                            B. Decraene
                                                           S. Litkowski
                                                                 Orange
                                                              R. Shakir
                                                                 Google
                                                          April 2, 2018

                   Segment Routing with MPLS data plane
                 draft-ietf-spring-segment-routing-mpls-13

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.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any

Filsfils, et al.       Expires October 2, 2018                 [Page 1]
Internet-Draft        Segment Routing with MPLS              April 2018

   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 October 2, 2018.

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
   (http://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
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction...................................................3
   2. MPLS Instantiation of Segment Routing..........................3
      2.1. Supporting Multiple Forwarding Behaviors for the Same Prefix
      ...............................................................4
      2.2. SID Representation in the MPLS Forwarding Plane...........4
      2.3. Segment Routing Global Block and Local Block..............5
      2.4. Mapping a SID Index to an MPLS label......................6
      2.5. Incoming Label Collision..................................6
         2.5.1. Tie-breaking Rules...................................8
         2.5.2. Redistribution between Routing Protocol Instances...11
            2.5.2.1. Illustration...................................11
      2.6. Outgoing Label Collision.................................11
      2.7. PUSH, CONTINUE, and NEXT.................................12
         2.7.1. PUSH................................................12
         2.7.2. CONTINUE............................................12
         2.7.3. NEXT................................................12
      2.8. MPLS Label downloaded to FIB corresponding to Global and
      Local SIDs....................................................13
      2.9. Active Segment...........................................13
      2.10. Forwarding behavior for Global SIDs.....................13
         2.10.1. Forwarding Behavior for PUSH and CONTINUE Operation for
         Global SIDs................................................13
         2.10.2. Forwarding Behavior for NEXT Operation for Global SIDs
         ...........................................................15

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