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Foreign Agent Error Extension for Mobile IPv4
RFC 4636

Document type: RFC - Proposed Standard (October 2006; Errata)
Updates RFC 3344
Document stream: IETF
Last updated: 2013-04-05
Other versions: plain text, pdf, html

IETF State: (None)
Consensus: Unknown
Document shepherd: No shepherd assigned

IESG State: RFC 4636 (Proposed Standard)
Responsible AD: Margaret Wasserman
Send notices to: mip4-chairs@tools.ietf.org

Network Working Group                                         C. Perkins
Request for Comments: 4636                         Nokia Research Center
Category: Standards Track                                   October 2006

             Foreign Agent Error Extension for Mobile IPv4

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 (2006).

Abstract

   This document specifies a new extension for use by Foreign Agents
   operating Mobile IP for IPv4.  Currently, a foreign agent cannot
   supply status information without destroying the ability for a mobile
   node to verify authentication data supplied by the home agent.  The
   new extension solves this problem by making a better place for the
   foreign agent to provide its status information to the mobile node.

Perkins                     Standards Track                     [Page 1]
RFC 4636                   FA Error Extension               October 2006

1.  Introduction

   This document specifies a new non-skippable extension for use by
   Foreign Agents operating Mobile IP for IPv4 [4].  The new extension
   option allows a foreign agent to supply an error code without
   disturbing the data supplied by the Home Agent within the
   Registration Reply message.  In this way, the mobile node can verify
   that the Registration Reply message was generated by the Home Agent
   even in cases where the foreign agent is required by protocol to
   insert new status information into the Registration Reply message.

2.  Terminology

   The keywords "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 [1].  Other
   terminology is used as already defined in [4].

3.  FA Error Extension Format

   The format of the FA Error Extension conforms to the Short Extension
   format specified for Mobile IPv4 [4].  The FA Error Extension is not
   skippable.

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |   Length      |    Sub-Type   |     Status    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         45

      Length

         2

      Sub-Type

         0

      Status

         A status code used by the foreign agent to supply status
         information to the mobile node.

Perkins                     Standards Track                     [Page 2]
RFC 4636                   FA Error Extension               October 2006

4.  Operation and Use of the FA Error Extension

   The FA Error Extension is only valid for use within Mobile IPv4
   Registration Reply messages.  The FA Error Extension is not
   skippable.  A mobile node that cannot correctly interpret the
   contents of the FA Error Extension MUST NOT use the care-of address
   provided in the Registration Reply message, until another
   Registration Request message has been sent and a successful
   Registration Reply message received.

   Status codes allowable for use within the FA Error Extension are
   within the range 64-127.  The currently specified codes are as
   follows:

      64 reason unspecified
      65 administratively prohibited
      66 insufficient resources
      68 home agent failed authentication
      71 poorly formed Reply
      77 invalid care-of address
      78 registration timeout

   as defined in RFC 3344 [4] for use by the Foreign Agent.  Status
   codes for use with the FA Error extensions must not be differently
   defined for use in the Code field of Registration Reply messages.

   When a foreign agent appends a FA Error Extension to the Registration
   Reply as received from the Home Agent, it has to update the UDP
   Length field in the UDP header [5] to account for the extra 4 bytes
   of length.

   This document updates the Mobile IP base specification [4] regarding
   the procedures followed by the foreign agent in the case that the
   home agent fails authentication.  Instead of modifying the "status"
   field of the Registration Reply to contain the value 68, now the

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