Anycast Segments in MPLS based SPRING
draft-psarkar-spring-mpls-anycast-segments-00

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SPRING Working Group                                      P. Sarkar, Ed.
Internet-Draft                                                H. Gredler
Intended status: Standards Track                  Juniper Networks, Inc.
Expires: January 7, 2016                                    July 6, 2015

                 Anycast Segments in MPLS based SPRING
             draft-psarkar-spring-mpls-anycast-segments-00

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.  [I-D.ietf-spring-segment-routing]
   extended the use of anycast addresses to a SPRING network, wherein a
   group of SPRING-capable devices can represent a anycast address, by
   having the same SRGB label block 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 SPRING, 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
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Internet-Draft    Anycast Segments in MPLS based SPRING        July 2015

   This Internet-Draft will expire on January 7, 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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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Solution  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  Anycast Segment Label . . . . . . . . . . . . . . . . . .   6
     3.2.  Virtual SID Label Lookup Table  . . . . . . . . . . . . .   7
     3.3.  Label Stack Computation . . . . . . . . . . . . . . . . .  10
     3.4.  Advertising Anycast Prefix Segments . . . . . . . . . . .  11
     3.5.  Programming Anycast Prefix Segments . . . . . . . . . . .  12
     3.6.  Packet Flow . . . . . . . . . . . . . . . . . . . . . . .  12
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   Anycast is a network addressing scheme and routing methodology in
   which packets from a single source device are forwarded to the
   topologically nearest node in a group of potential receiving devices,
   all identified by the same anycast address.  There are various useful
   usecases of anycast addresses, and discussion of the same are outside
   the scope of this document.

   [I-D.ietf-spring-segment-routing] extended the use of anycast
   addresses to SPRING networks.  An operator may combine a group of
   SPRING-enabled nodes to form a anycast group, by picking a anycast

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