Mobility Header Home Agent Switch Message
RFC 5142

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Network Working Group                                           B. Haley
Request for Comments: 5142                               Hewlett-Packard
Category: Standards Track                                 V. Devarapalli
                                                         Azaire Networks
                                                                 H. Deng
                                                            China Mobile
                                                                J. Kempf
                                                         DoCoMo USA Labs
                                                            January 2008

               Mobility Header Home Agent Switch Message

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.

Abstract

   This document specifies a new Mobility Header message type that can
   be used between a home agent and mobile node to signal to a mobile
   node that it should acquire a new home agent.

Haley, et al.               Standards Track                     [Page 1]
RFC 5142               Home Agent Switch Message            January 2008

Table of Contents

   1. Introduction ....................................................2
   2. Terminology .....................................................3
   3. Scenarios .......................................................3
      3.1. Overloaded .................................................3
      3.2. Load Balancing .............................................3
      3.3. Maintenance ................................................3
      3.4. Functional Load Balancing ..................................3
      3.5. Home Agent Renumbering .....................................4
   4. Home Agent Switch Message .......................................4
   5. Home Agent Operation ............................................6
      5.1. Sending Home Agent Switch Messages .........................6
      5.2. Retransmissions ............................................7
      5.3. Mobile Node Errors .........................................7
   6. Mobile Node Operation ...........................................8
      6.1. Receiving Home Agent Switch Messages .......................8
      6.2. Selecting a Home Agent .....................................9
   7. Operational Considerations ......................................9
   8. Protocol Constants .............................................10
   9. IANA Considerations ............................................10
   10. Security Considerations .......................................10
   11. References ....................................................11
      11.1. Normative References .....................................11
      11.2. Informative References ...................................11
   Acknowledgments ...................................................11

1.  Introduction

   RFC 3775 [RFC3775] contains no provision to allow a home agent to
   inform a mobile node that it needs to stop acting as the home agent
   for the mobile node.  For example, a home agent may wish to handoff
   some of its mobile nodes to another home agent because it has become
   overloaded or it is going offline.

   This protocol describes a signaling message, called the Home Agent
   Switch message, that can be used to send a handoff notification
   between a home agent and mobile node.

   The Home Agent Switch message does not attempt to solve all general
   problems related to changing the home agent of a mobile node.  In
   particular, this protocol does not attempt to solve:

      o  The case where the Home Address of a mobile node must change in
         order to switch to a new home agent.  This operation should be
         avoided using this message.

Haley, et al.               Standards Track                     [Page 2]
RFC 5142               Home Agent Switch Message            January 2008

      o  Determining when a home agent should actively move mobile nodes
         to another home agent.  This decision should be made by a
         backend protocol, for example, as described in [hareliability].

2.  Terminology

   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].

3.  Scenarios

   Here are some example scenarios where a home agent signaling message
   would be useful.

3.1.  Overloaded

   There are a number of reasons a home agent might be considered
   overloaded.  One might be that it is at, or near, its limit on the