Architectural Approaches to Multi-homing for IPv6
RFC 4177

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Network Working Group                                          G. Huston
Request for Comments: 4177                                         APNIC
Category: Informational                                   September 2005

           Architectural Approaches to Multi-homing for IPv6

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This memo provides an analysis of the architectural aspects of
   multi-homing support for the IPv6 protocol suite.  The purpose of
   this analysis is to provide a taxonomy for classification of various
   proposed approaches to multi-homing.  It is also an objective of this
   exercise to identify common aspects of this domain of study, and also
   to provide a framework that can allow exploration of some of the
   further implications of various architectural extensions that are
   intended to support multi-homing.

Huston                       Informational                      [Page 1]
RFC 4177                  Multi6 Architecture             September 2005

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  The Multi-Homing Space . . . . . . . . . . . . . . . . . . . .  5
   4.  Functional Goals and Considerations  . . . . . . . . . . . . .  7
   5.  Approaches to Multi-Homing . . . . . . . . . . . . . . . . . .  7
       5.1.  Multi-Homing: Routing  . . . . . . . . . . . . . . . . .  8
       5.2.  Multi-Homing: Mobility . . . . . . . . . . . . . . . . .  9
       5.3.  Multi-homing: Identity Considerations  . . . . . . . . . 12
       5.4.  Multi-homing: Identity Protocol Element  . . . . . . . . 14
       5.5.  Multi-homing: Modified Protocol Element  . . . . . . . . 15
       5.6.  Modified Site-Exit and Host Behaviors  . . . . . . . . . 16
   6.  Approaches to Endpoint Identity  . . . . . . . . . . . . . . . 17
       6.1.  Endpoint Identity Structure  . . . . . . . . . . . . . . 18
       6.2.  Persistent, Opportunistic, and Ephemeral Identities  . . 20
       6.3.  Common Issues for Multi-Homing Approaches  . . . . . . . 23
             6.3.1.  Triggering Locator Switches  . . . . . . . . . . 23
             6.3.2.  Locator Selection  . . . . . . . . . . . . . . . 26
             6.3.3.  Layering Identity  . . . . . . . . . . . . . . . 27
             6.3.4.  Session Startup and Maintenance  . . . . . . . . 29
             6.3.5.  Dynamic Capability Negotiation . . . . . . . . . 31
             6.3.6.  Identity Uniqueness and Stability  . . . . . . . 31
   7.  Functional Decomposition of Multi-Homing Approaches  . . . . . 32
       7.1.  Establishing Session State . . . . . . . . . . . . . . . 32
       7.2.  Re-homing Triggers . . . . . . . . . . . . . . . . . . . 33
       7.3.  Re-homing Locator Pair Selection . . . . . . . . . . . . 33
       7.4.  Locator Change . . . . . . . . . . . . . . . . . . . . . 34
       7.5.  Removal of Session State . . . . . . . . . . . . . . . . 34
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 34
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 34
   10. Informative References . . . . . . . . . . . . . . . . . . . . 34

Huston                       Informational                      [Page 2]
RFC 4177                  Multi6 Architecture             September 2005

1.  Introduction

   The objective of this analysis is to allow various technical
   proposals relating to the support of multi-homing environment in IPv6
   to be placed within an architectural taxonomy.  This is intended to
   allow these proposals to be classified and compared in a structured
   fashion.  It is also an objective of this exercise to identify common
   aspects across all proposals within this domain of study, and also to
   provide a framework that can allow exploration of some of the further
   implications of various architectural extensions that are intended to
   support multi-homing.  The scope of this study is limited to the IPv6
   protocol suite architecture, although reference is made to IPv4
   approaches as required.

2.  Terminology

   Care-of Address (CoA)
      A unicast routeable address associated with a mobile node while
      visiting a foreign link; the subnet prefix of this IP address is a
      foreign subnet prefix.  Among the multiple care-of addresses that
      a mobile node may have at any given time (e.g., with different
      subnet prefixes), the one registered with the mobile node's home
      agent for a given home address is called its "primary" care-of
      address.

   Correspondent Node (CN)
      A peer node with which a mobile node is communicating.  The
      correspondent node may be either mobile or stationary.