Segment Routing Recursive Information
draft-filsfils-spring-sr-recursing-info-05

Document Type Active Internet-Draft (candidate for spring WG)
Last updated 2017-06-20
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SPRING                                                       C. Filsfils
Internet-Draft                                                S. Previdi
Intended status: Standards Track                               P. Psenak
Expires: December 22, 2017                                   L. Ginsberg
                                                     Cisco Systems, Inc.
                                                           June 20, 2017

                 Segment Routing Recursive Information
               draft-filsfils-spring-sr-recursing-info-05

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).

   There are use cases where it is desirable to utilize a SID associated
   with a given node in order to transport traffic destined to different
   local services supported by such node.  This document defines the
   mechanism to do so and illustrates it.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

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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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 22, 2017.

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Copyright Notice

   Copyright (c) 2017 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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Segment Routing Recursing Information (SRRI)  . . . . . . . .   3
   4.  Illustration  . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Reference Diagram . . . . . . . . . . . . . . . . . . . .   5
     4.2.  Description . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Benefits  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Segment Routing (SR) as defined in [I-D.ietf-spring-segment-routing]
   utilizes forwarding instructions called "segments" to direct packets
   through the network.  When an MPLS dataplane is in use Segment
   Identifiers (SIDs) are assigned to prefixes and are associated with a
   specific algorithm.  SIDs may be Local or Global in scope.  When a
   SID has global scope the SID is mapped via the Segment Routing Global
   Block (SRGB) to a node specific label which acts as the forwarding
   instruction.

   There are use cases where it is desirable to utilize a SID associated
   with a node N to transport traffic destined to different local
   services supported by N.  This document defines the mechanism to do
   so and illustrates it.

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