Candidate Access Router Discovery (CARD)
RFC 4066

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Network Working Group                                    M. Liebsch, Ed.
Request for Comments: 4066                                 A. Singh, Ed.
Category: Experimental                                        H. Chaskar
                                                               D. Funato
                                                                 E. Shim
                                                               July 2005

                Candidate Access Router Discovery (CARD)

Status of This Memo

   This memo defines an Experimental Protocol for the Internet
   community.  It does not specify an Internet standard of any kind.
   Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   To enable seamless IP-layer handover of a mobile node (MN) from one
   access router (AR) to another, the MN is required to discover the
   identities and capabilities of candidate ARs (CARs) for handover
   prior to the initiation of the handover.  The act of discovery of
   CARs has two aspects: identifying the IP addresses of the CARs and
   finding their capabilities.  This process is called "candidate access
   router discovery" (CARD).  At the time of IP-layer handover, the CAR,
   whose capabilities are a good match to the preferences of the MN, is
   chosen as the target AR for handover.  The protocol described in this
   document allows a mobile node to perform CARD.

Table of Contents

   1.  Introduction..................................................  2
   2.  Terminology...................................................  3
   3.  CARD Protocol Functions.......................................  4
       3.1.  Reverse Address Translation.............................  4
       3.2.  Discovery of CAR Capabilities...........................  4
   4.  CARD Protocol Operation.......................................  4
       4.1.  Conceptual Data Structures..............................  7
       4.2.  Mobile Node - Access Router Operation...................  8
       4.3.  Current Access Router - Candidate Access Router
             Operation............................................... 11
       4.4.  CARD Protocol Message Piggybacking on the MN-AR
             Interface............................................... 13

Liebsch, et al.               Experimental                      [Page 1]
RFC 4066        Candidate Access Router Discovery (CARD)       July 2005

   5.  Protocol Messages............................................. 14
       5.1.  CARD Messages for the Mobile Node-Access Router
             Interface............................................... 14
       5.2.  CARD Inter-Access Router Messages....................... 28
   6.  Security Considerations....................................... 31
       6.1.  Veracity of CARD Information............................ 31
       6.2.  Security Association between AR and AR.................. 31
       6.3.  Security Association between AR and MN.................. 32
       6.4.  Router Certificate Exchange............................. 32
       6.5.  DoS Attack.............................................. 34
       6.6.  Replay Attacks.......................................... 34
   7.  Protocol Constants............................................ 34
   8.  IANA Considerations........................................... 35
   9.  Normative References.......................................... 35
   10. Informative References........................................ 35
   11. Contributors.................................................. 36
   12. Acknowledgements.............................................. 36
   Appendix A.  Maintenance of Address Mapping Tables in
                Access Routers....................................... 37
       Appendix A.1. Centralized Approach Using a Server Functional
                     Entity.......................................... 37
       Appendix A.2. Decentralized Approach Using Mobile Terminals'
                     Handover........................................ 38
   Appendix B.  Application Scenarios................................ 40
       Appendix B.1. CARD Operation in a Mobile IPv6-Enabled Wireless
                     LAN Network..................................... 40
       Appendix B.2. CARD Operation in a Fast Mobile IPv6-Enabled
                     Network......................................... 43

1.  Introduction

   IP mobility protocols, such as Mobile IP, enable mobile nodes to
   execute IP-level handover among access routers.  Work is underway
   [Kood03][Malk03] to extend the mobility protocols to allow seamless
   IP handover.  Seamless IP mobility protocols will require knowledge
   of candidate access routers (CARs) to which a mobile node can be
   transferred.  The CAR discovery protocol enables the acquisition of
   information about the access routers that are candidates for the