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Network Working Group                                           K. LeungRequest for Comments: 4332                                      A. PatelCategory: Informational                                    Cisco Systems                                                             G. Tsirtsis                                                    Flarion Technologies                                                             E. Klovning                                                 Birdstep Technology ASA                                                           December 2005Cisco's Mobile IPv4 Host Configuration ExtensionsStatus 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.  SeeRFC 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 theLeung, 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 Contents1. Introduction ....................................................22. Host Configuration Extensions Summary ...........................33. Host Configuration Extensions ...................................43.1. Host Configuration Request Extension .......................53.2. Home Network Length Prefix Extension .......................53.3. DNS Server Extension .......................................63.4. DHCP Server Extension ......................................63.5. DHCP Client ID Extension ...................................73.6. Default Gateway Extension ..................................73.7. DNS Suffix Extension .......................................83.8. Configuration URL Extension ................................84. Security Considerations .........................................95. Acknowledgements ................................................96. Informative References ..........................................91.  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 theLeung, 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 insection 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:         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.Leung, et al.                Informational                      [Page 5]

RFC 4332                      Host Config                  December 20053.3.  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 20053.5.  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 20053.7.  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 20054.  Security Considerations   The host configuration extensions follow the same rules for Mobile IP   extensions in registration messages.  See the Security Considerations   section inRFC 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 2005Authors' 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.comLeung, et al.                Informational                     [Page 10]

RFC 4332                      Host Config                  December 2005Full Copyright Statement   Copyright (C) The Internet Society (2005).   This document is subject to the rights, licenses and restrictions   contained inBCP 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.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at ietf-   ipr@ietf.org.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Leung, et al.                Informational                     [Page 11]