Anycast Segments in MPLS based Segment Routing
draft-psarkar-spring-mpls-anycast-segments-01

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SPRING Working Group                                      P. Sarkar, Ed.
Internet-Draft                                    Juniper Networks, Inc.
Intended status: Standards Track                              H. Gredler
Expires: April 11, 2016                           Individual Contributor
                                                             C. Filsfils
                                                              S. Previdi
                                                     Cisco Systems, Inc.
                                                             B. Decraene
                                                                  Orange
                                                            M. Horneffer
                                                        Deutsche Telekom
                                                         October 9, 2015

             Anycast Segments in MPLS based Segment Routing
             draft-psarkar-spring-mpls-anycast-segments-01

Abstract

   Instead of forwarding to a specific device or to all devices in a
   group, anycast addresses, let network devices forward a packet to (or
   steer it through) one or more topologically nearest devices in a
   specific group of network devices.  The use of anycast addresses has
   been extended to the Segment Routing (SR) network, wherein a group of
   SR-capable devices can represent a anycast address, by having the
   same Segment Routing Global Block (SRGB) provisioned on all the
   devices and each one of them advertising the same anycast prefix
   segment (or Anycast SID).

   This document describes a proposal for implementing anycast prefix
   segments in a MPLS-based SR network, without the need to have the
   same SRGB block (label ranges) provisioned across all the member
   devices in the group.  Each node can be provisioned with a separate
   SRGB from the label range supported by the specfic hardware platform.

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

Sarkar, et al.           Expires April 11, 2016                 [Page 1]
Internet-Draft      Anycast Segments in MPLS-based SR       October 2015

   working documents as Internet-Drafts.  The list of current Internet-
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   This Internet-Draft will expire on April 11, 2016.

Copyright Notice

   Copyright (c) 2015 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
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Solution  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Definitions . . . . . . . . . . . . . . . . . . . . . . .   7
       3.1.1.  Common Anycast SRGB (CA-SRGB) . . . . . . . . . . . .   7
       3.1.2.  Common Anycast Prefix Segment Label (CAPSL) . . . . .   8
       3.1.3.  Anycast Prefix Segment Label (APSL) . . . . . . . . .   8
     3.2.  Procedures  . . . . . . . . . . . . . . . . . . . . . . .   9
       3.2.1.  Label Stack Computation . . . . . . . . . . . . . . .   9
       3.2.2.  Virtual SID Label Lookup Table  . . . . . . . . . . .  10
       3.2.3.  Advertising Anycast Prefix Segments . . . . . . . . .  13
       3.2.4.  Programming Anycast Prefix Segments . . . . . . . . .  14
     3.3.  Packet Flow . . . . . . . . . . . . . . . . . . . . . . .  16
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  17
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
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