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



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  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
  fundamental configuration associated with the home network via the





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  Home Agent.  These extensions provide information for home subnet
  prefix, DNS server, DHCP server, DHCP client identifier, default
  gateway, DNS suffix, and configuration URL.

2.  Host Configuration Extensions Summary

  The following Cisco vendor-specific extensions provide the host
  configuration for a Mobile Node.  The "Host Configuration Request"
  extension is allowed only in the Registration Request.  The rest of
  the extensions are appended in the Registration Reply.

  o  Host Configuration Request

     *  Request for host configuration information from the Mobile Node
        to the Home Agent.

  o  Home Network Prefix Length

     *  The length of the subnet prefix on the home network.

  o  Default Gateway

     *  The default gateway's IP address on the home network.

  o  DNS Server

     *  The DNS server's IP address in the home network.

  o  DNS Suffix

     *  The DNS suffix for hostname resolution in the home network.

  o  DHCP Client ID

     *  The DHCP Client ID used to obtain the IP address.  When the
        Mobile Node returns home and is responsible for managing its
        own address, this information maps to the client identifier
        option as defined in section 9.14 of [RFC2132] and referenced
        in [RFC2131].

  o  DHCP Server

     *  The DHCP server's IP address in the home network.

  o  Configuration URL

     *  The URL for the Mobile Node to download configuration
        parameters from a server.



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  When the Mobile Node needs to obtain its host configuration, the Host
  Configuration Request VSE is appended to the Registration Request.
  This VSE indicates to the Home Agent that either all or selected host
  configuration VSEs need to be appended to the Registration Reply.  If
  the Home Agent retrieved the information from a DHCP server (in Proxy
  DHCP mode), then the DHCP Client ID and DHCP Server extensions are
  appended in the Registration Reply.  These DHCP-related extensions
  are populated with values that had been used in the DHCP messages
  exchanged between the Home Agent and the DHCP server.

  The VSEs are authenticated as part of the registration message using
  any of the authentication mechanism defined for Mobile IP ([RFC3344],
  [RFC3012]).

  This message MAY contain extensions defined in Mobile IP, including
  vendor-specific extensions [RFC3115].

3.  Host Configuration Extensions

  Cisco's host configuration extensions to Mobile IPv4 are based on the
  vendor-specific extensions defined in [RFC3115].  The format of the
  VSE TLV (Type-Length-Value) is as follows:

   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      |          Reserved             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Vendor/Org-ID                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Vendor-NVSE-Type        |     Vendor-NVSE-Value ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Type: 134

    Length:

       Indicates the length (in bytes) of the data field within this
       extension, excluding the Type and Length fields.

    Reserved:

       Reserved for future use.  To be set to 0 while sending, ignored
       on reception.

    Vendor/Org-ID:

       9 (Cisco Systems)



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    Vendor-NVSE-Type:

       14 (Host Configuration)

    Vendor-NVSE-Value:

       Format is shown below for each subtype.  The Sub-Type field is
       an integer from 0 to 255.

3.1.  Host Configuration Request Extension

  This format of the Host Configuration Request extension is shown
  below.

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           Sub-Type            |           Selector            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Sub-Type:

        0

     Selector:

        0 indicates all host configuration available to the Home
        Agent (HA) is requested by the Mobile Node.

3.2.  Home Network Length Prefix Extension

  This format of the Home Network Prefix Length extension is shown
  below.

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           Sub-Type            |        Prefix Length          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Sub-Type:

        1

     Prefix Length:

        The number of bits in the home subnet prefix.




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3.3.  DNS Server Extension

  This format of the DNS Server extension is shown below.

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           Sub-Type            |        Primary DNS Server
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                . . .               |        Secondary DNS Server
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                . . .               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Sub-Type:

        2

     Primary DNS Server:

        The IP address of the primary DNS server.

     Secondary DNS Server:

        The IP address of the secondary DNS server.

3.4.  DHCP Server Extension

  This format of the DHCP Server extension is shown below.

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           Sub-Type            |          DHCP Server
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                . . .               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Sub-Type:

        3

     DHCP Server:

        The IP address of the DHCP server.






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3.5.  DHCP Client ID Extension

  This format of the DHCP Client ID extension is shown below.

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           Sub-Type            |          Client ID . . .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Sub-Type:

        4

     Client ID:

        DHCP servers use this value to index their database of address
        bindings.  This value is expected to be unique for all clients
        in an administrative domain.  The size of field is between 2
        and 255 octets.

3.6.  Default Gateway Extension

  This format of the Default Gateway extension is shown below.

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           Sub-Type            |          Default Gateway
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                . . .               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Sub-Type:

        5

     Default Gateway:

        The IP address of the default gateway for the Mobile Node on
        the home network.










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3.7.  DNS Suffix Extension

  This format of the DNS Suffix extension is shown below.

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           Sub-Type            |         DNS Suffix . . .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Sub-Type:

        6

     DNS Suffix:

        The DNS suffix to be appended to the name of Mobile Node when
        completing its fully qualified domain name (FQDN).  The size of
        field is between 1 and 246 octets.

3.8.  Configuration URL Extension

  This format of the Configuration URL extension is shown below.

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           Sub-Type            |         URL String . . .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Sub-Type:

        7

     URL String:

        The Mobile Node can retrieve configuration parameters via the
        URL.  The URL is at most 246 bytes in length.













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4.  Security Considerations

  The host configuration extensions follow the same rules for Mobile IP
  extensions in registration messages.  See the Security Considerations
  section in RFC 3344.

  The Configuration URL extension may trigger the Mobile Node to
  download the configuration parameters from a server.  The protection
  of the data transfer is outside the scope of this document.  Possible
  options include encryption of data before transfer or using HTTPS.

5.  Acknowledgements

  The authors would like to acknowledge Jayshree Bharatia, Kuntal
  Chowdhury, Avi Lior, and Lila Madour for their contributions to the
  work in progress titled "Mobile IPv4 Extension for Configuration
  Options Exchange".

6.  Informative References

  [RFC1332]  McGregor, G., "The PPP Internet Protocol Control Protocol
             (IPCP)", RFC 1332, May 1992.

  [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
             RFC 2131, March 1997.

  [RFC2132]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
             Extensions", RFC 2132, March 1997.

  [RFC3012]  Perkins, C. and P. Calhoun, "Mobile IPv4 Challenge/
             Response Extensions", RFC 3012, November 2000.

  [RFC3115]  Dommety, G. and K. Leung, "Mobile IP Vendor/
             Organization-Specific Extensions", RFC 3115, April 2001.

  [RFC3344]  Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
             August 2002.














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Authors' Addresses

  Kent Leung
  Cisco Systems
  170 W. Tasman Drive
  San Jose, CA  95134
  US

  Phone: +1 408-526-5030
  EMail: [email protected]


  Alpesh Patel
  Cisco Systems
  170 W. Tasman Drive
  San Jose, CA  95134
  US

  Phone: +1 408-853-9580
  EMail: [email protected]


  George Tsirtsis
  Flarion Technologies
  Bedminster One
  135 Route 202/206 South
  Bedminster, NJ  07921
  US

  Phone: +1 908-947-7059
  EMail: [email protected]


  Espen Klovning
  Birdstep Technology ASA
  Bryggegata 7
  Oslo,   0250
  Norway

  Phone: +47 95 20 26 29
  EMail: [email protected]










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Acknowledgement

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