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rfc:rfc4332

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
 fundamental configuration associated with the home network via the

Leung, et al. Informational [Page 2] RFC 4332 Host Config December 2005

 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.

Leung, et al. Informational [Page 3] RFC 4332 Host Config December 2005

 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)

Leung, et al. Informational [Page 4] RFC 4332 Host Config December 2005

   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:
    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.

Leung, et al. Informational [Page 5] RFC 4332 Host Config December 2005

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.

Leung, et al. Informational [Page 6] RFC 4332 Host Config December 2005

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.

Leung, et al. Informational [Page 7] RFC 4332 Host Config December 2005

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.

Leung, et al. Informational [Page 8] RFC 4332 Host Config December 2005

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.

Leung, et al. Informational [Page 9] RFC 4332 Host Config December 2005

Authors' Addresses

 Kent Leung
 Cisco Systems
 170 W. Tasman Drive
 San Jose, CA  95134
 US
 Phone: +1 408-526-5030
 EMail: kleung@cisco.com
 Alpesh Patel
 Cisco Systems
 170 W. Tasman Drive
 San Jose, CA  95134
 US
 Phone: +1 408-853-9580
 EMail: alpesh@cisco.com
 George Tsirtsis
 Flarion Technologies
 Bedminster One
 135 Route 202/206 South
 Bedminster, NJ  07921
 US
 Phone: +1 908-947-7059
 EMail: g.tsirtsis@flarion.com
 Espen Klovning
 Birdstep Technology ASA
 Bryggegata 7
 Oslo,   0250
 Norway
 Phone: +47 95 20 26 29
 EMail: espen@birdstep.com

Leung, et al. Informational [Page 10] RFC 4332 Host Config December 2005

Full Copyright Statement

 Copyright (C) The Internet Society (2005).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78 and at www.rfc-editor.org/copyright.html, and
 except as set forth therein, the authors retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

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Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Leung, et al. Informational [Page 11]

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