Reverse Tunneling for Mobile IP, revised
RFC 3024

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Network Working Group                              G. Montenegro, Editor
Request for Comments: 3024                        Sun Microsystems, Inc.
Obsoletes: 2344                                             January 2001
Category: Standards Track

                Reverse Tunneling for Mobile IP, revised

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

   Mobile Internet Protocol (IP) uses tunneling from the home agent to
   the mobile node's care-of address, but rarely in the reverse
   direction.  Usually, a mobile node sends its packets through a router
   on the foreign network, and assumes that routing is independent of
   source address.  When this assumption is not true, it is convenient
   to establish a topologically correct reverse tunnel from the care-of
   address to the home agent.

   This document proposes backwards-compatible extensions to Mobile IP
   to support topologically correct reverse tunnels.  This document does
   not attempt to solve the problems posed by firewalls located between
   the home agent and the mobile node's care-of address.

   This document obsoletes RFC 2344.

Montenegro                  Standards Track                     [Page 1]
RFC 3024        Reverse Tunneling for Mobile IP, revised    January 2001

Table of Contents

   1. Introduction ...................................................  3
   1.1. Terminology ..................................................  4
   1.2. Assumptions ..................................................  4
   1.3. Justification ................................................  5
   2. Overview .......................................................  5
   3. New Packet Formats .............................................  6
   3.1. Mobility Agent Advertisement Extension .......................  6
   3.2. Registration Request .........................................  6
   3.3. Encapsulating Delivery Style Extension .......................  7
   3.4. New Registration Reply Codes .................................  8
   4. Changes in Protocol Behavior ...................................  9
   4.1. Mobile Node Considerations ...................................  9
   4.1.1. Sending Registration Requests to the Foreign Agent .........  9
   4.1.2. Receiving Registration Replies from the Foreign Agent ...... 10
   4.2. Foreign Agent Considerations ................................. 10
   4.2.1. Receiving Registration Requests from the Mobile Node ....... 11
   4.2.2. Relaying Registration Requests to the Home Agent ........... 11
   4.3. Home Agent Considerations .................................... 11
   4.3.1. Receiving Registration Requests from the Foreign Agent ..... 12
   4.3.2. Sending Registration Replies to the Foreign Agent .......... 12
   5. Mobile Node to Foreign Agent Delivery Styles ................... 13
   5.1. Direct Delivery Style ........................................ 13
   5.1.1. Packet Processing .......................................... 13
   5.1.2. Packet Header Format and Fields ............................ 13
   5.2. Encapsulating Delivery Style ................................. 14
   5.2.1 Packet Processing ........................................... 14
   5.2.2. Packet Header Format and Fields ............................ 15
   5.3. Support for Broadcast and Multicast Datagrams ................ 16
   5.4. Selective Reverse Tunneling .................................. 16
   6. Security Considerations ........................................ 17
   6.1. Reverse-tunnel Hijacking and Denial-of-Service Attacks ....... 17
   6.2. Ingress Filtering ............................................ 18
   6.3. Reverse Tunneling for Disparate Address Spaces ............... 18
   7. IANA Considerations ............................................ 18
   8. Acknowledgements ............................................... 18
   References ........................................................ 19
   Editor and Chair Addresses ........................................ 20
   Appendix A: Disparate Address Space Support ....................... 21
      A.1. Scope of the Reverse Tunneling Solution ................... 21
      A.2. Terminating Forward Tunnels at the Foreign Agent .......... 24
      A.3. Initiating Reverse Tunnels at the Foreign Agent ........... 26
      A.4. Limited Private Address Scenario .......................... 26
   Appendix B: Changes from RFC2344 .................................. 29
   Full Copyright Statement .......................................... 30

Montenegro                  Standards Track                     [Page 2]