Cisco's Mobile IPv4 Host Configuration Extensions
RFC 4332

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Network Working Group                                           K. Leung
Request for Comments: 4332                                      A. Patel
Category: Informational                                    Cisco Systems
                                                             G. Tsirtsis
                                                    Flarion Technologies
                                                             E. Klovning
                                                 Birdstep Technology ASA
                                                           December 2005

           Cisco's Mobile IPv4 Host Configuration Extensions

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).

IESG Note

   This RFC is not a candidate for any level of Internet Standard.  The
   IETF disclaims any knowledge of the fitness of this RFC for any
   purpose and in particular notes that the decision to publish is not
   based on IETF review for such things as security, congestion control,
   or inappropriate interaction with deployed protocols.  The RFC Editor
   has chosen to publish this document at its discretion.  Readers of
   this document should exercise caution in evaluating its value for
   implementation and deployment.  See RFC 3932 for more information.

   This RFC does not offer any security mechanisms to provide data
   origin authentication and integrity, yet these security services are
   vitally important in this context.

Abstract

   An IP device requires basic host configuration to be able to
   communicate.  For example, it will typically require an IP address
   and the address of a DNS server.  This information is configured
   statically or obtained dynamically using Dynamic Host Configuration
   Protocol (DHCP) or Point-to-Point Protocol/IP Control Protocol
   (PPP/IPCP).  However, both DHCP and PPP/IPCP provide host
   configuration based on the access network.  In Mobile IPv4, the
   registration process boots up a Mobile Node at an access network,
   also known as a foreign network.  The information to configure the

Leung, et al.                Informational                      [Page 1]
RFC 4332                      Host Config                  December 2005

   host needs to be based on the home network.  This document describes
   the Cisco vendor-specific extensions to Mobile IPv4 to provide the
   base host configuration in Registration Request and Reply messages.

Table of Contents

   1. Introduction ....................................................2
   2. Host Configuration Extensions Summary ...........................3
   3. Host Configuration Extensions ...................................4
      3.1. Host Configuration Request Extension .......................5
      3.2. Home Network Length Prefix Extension .......................5
      3.3. DNS Server Extension .......................................6
      3.4. DHCP Server Extension ......................................6
      3.5. DHCP Client ID Extension ...................................7
      3.6. Default Gateway Extension ..................................7
      3.7. DNS Suffix Extension .......................................8
      3.8. Configuration URL Extension ................................8
   4. Security Considerations .........................................9
   5. Acknowledgements ................................................9
   6. Informative References ..........................................9

1.  Introduction

   An IPv4 device requires some basic configuration to communicate with
   other nodes.  Typically, it has an IP address for an interface and
   DNS server's IP address to resolve the peer's hostname to an IP
   address.  DHCP [RFC2131] and PPP/IPCP [RFC1332] provide host
   configuration information on the access network interface, but this
   is inadequate in a Mobile IPv4 environment.  In Mobile IPv4
   [RFC3344], a Mobile Node has a virtual network interface on the home
   network, anchored by the Home Agent.  The IP address, home subnet
   prefix, default gateway, and home network's DNS servers are essential
   in the boot up of a network interface.  In some cases, these are the
   only pieces of information needed by the Mobile Node.

   The Mobile IPv4 registration process provides the mechanism for a
   Mobile Node to boot up on a foreign network.  Upon the successful
   registration, the Mobile Node can communicate with the Correspondent
   Node.  The need to provide an efficient method to obtain the host
   configuration exists.  If the Mobile Node is a DHCP client, it can
   obtain configuration parameters from the DHCP server in the home
   network after the initial registration.

   This document introduces the Cisco vendor-specific extensions (VSEs)
   [RFC3115] to provide the means for a Mobile Node to download some