From perk@watson.ibm.com Fri Mar 3 08:42:02 1995 From: perk@watson.ibm.com (Charlie Perkins) To: iana@ISI.EDU Cc: jkrey@ISI.EDU, droms@bucknell.edu Subject: Getting a number assigned for a new DHCP option Date: Fri, 03 Mar 95 11:41:55 -0500 Content-Length: 10684 Status: RO X-Lines: 350 I would like to request a new DHCP option number for the following proposed mobile home address option. The following Internet Draft outlines the desired function. Briefly, mobile hosts need to specify to the DHCP server that they need a home address, instead of the IP address that would be issued by the DHCP server in reply to currently standard DHCP client requests. I am submitting the following proposal as an Internet Draft, and I hope to discuss it in the DHCP mailing list and working group at the next IETF meeting. Regards, Charles Perkins ======================================================================== Internet Engineering Task Force C. Perkins INTERNET DRAFT IBM 3 March 1995 DHCP Home Address option draft-perkins-homeaddr-dhcpopt-00.txt Abstract This draft defines a new option in the Bootstrap Protocol (BOOTP) and the Dynamic Host Configuration Protocol (DHCP) to enable mobile hosts, that obey the mobile-IP specification under consideration in the mobile-IP working group (afterwards just called "mobile hosts"), to configure themselves automatically. The option enables a mobile host to derive an mobile home address, and determine the subnet mask for the home network. Terminology defined in the mobile-IP draft specification and the DHCP specification applies here. Status of This Memo This document is a submission to the DHCP Working Group of the Internet Engineering Task Force (IETF). Comments should be submitted either to the author, or to the DHCP mailing list. Distribution of this memo is unlimited. This document is an Internet-Draft. Internet Drafts are working documents of the Internet Engineering Task Force (IETF), its Areas, and its Working Groups. Note that other groups may also distribute working documents as Internet Drafts. Internet Drafts are draft documents valid for a maximum of six months, and may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet Drafts as reference material, or to cite them other than as a ``working draft'' or ``work in progress.'' To learn the current status of any Internet-Draft, please check the ``1id-abstracts.txt'' listing contained in the internet-drafts Shadow Directories on ds.internic.net (US East Coast), nic.nordu.net (Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim). Perkins Expires 3 September 1995 [Page i] Internet Draft DHCP Home Address Option 3 March 1995 Contents Abstract i Status of This Memo i 1. Introduction 1 2. Mobile Home Address Option 1 3. Using BOOTP to acquire mobility configuration information 2 4. Using DHCP to acquire mobility configuration information 2 5. Acknowledgements 4 Author's Address 4 Perkins Expires 3 September 1995 [Page ii] Internet Draft DHCP Home Address Option 3 March 1995 1. Introduction This draft defines a new option in the Bootstrap Protocol (BOOTP)([2],[5]) and the Dynamic Host Configuration Protocol (DHCP)([3]) to enable mobile hosts to configure themselves automatically. The changes are intended to be useful to mobile hosts, which in this document are defined to be those host computers that conform to mobile-IP draft specification([4]). To use this method of autoconfiguration, a mobile host must also be a DHCP client -- that is, be capable of sending and receiving DHCP packets. The draft defines one new DHCP option (also called a BOOTP vendor extension): the 'mobile home address' option. The option is used by a BOOTP/DHCP server to communicate information to a client. The home address is used by a mobile host to register its local care-of address. The care-of address can also be obtained via DHCP, but that operation places no new requirements on the DHCP server, and can be completed by the normal means available to DHCP clients. The existing DHCP options are currently insufficient, because the IP address desired by the mobile host should be allocated from a pool of address managed by a mobile-IP home agent, and not necessarily related to the particular network from which the client's request emanates. This draft updates the list of DHCP options and BOOTP vendor extensions in RFC 1533. The option defined in this document consists of a tag octet and a length octet followed by the value of the option. The length octet contains the length in octets of the option value. The values of the option are in network byte order. 2. Mobile Home Address Option When this option is present in a DHCPDISCOVER message, the DHCP server is asked to send an appropriate home address to the mobile host, which address is configured by the local administration to be associated with a mobile home agent. The DHCP server, in its corresponding DHCPOFFER message, will insert the requested address into the usual place for requested IP addresses, namely the 'yiaddr' field. If the DHCP server wishes to also notify the mobile host of one of its home agents' addresses (and this will normally be the case), that home agent's IP address is inserted in the data field of the mobile home address option. It is anticipated that the mobile-IP working group will approve one of the current proposals for allowing a mobile host, with its already Perkins Expires 3 September 1995 [Page 1] Internet Draft DHCP Home Address Option 3 March 1995 known mobile home address, to dynamically discover the location of a home agent serving the home address. In that case, the DHCP server may be configured to send out mobile home addresses and expect that the mobile host discover the home agent's address by whichever method is approved by the working group. It is also anticipated that many installations will allow several home agents to serve the same mobile home addresses, for redundancy or load sharing. For this reason, we have also allowed for the possibility that the DHCP server may wish to insert multiple home agent addresses in the new option. The code for the mobile home address option is <68> as assigned by the IANA. The length is either four octets multiplied by the number of home agents supplied in the option, which may be zero or more. It is expected that the usual length will be four octets, containing a single home agent's address. Code Len Home Agent Addresses (zero or more) +----+----+ - -+ - -+ - -+ - -+ - -+ - -+ - -+ | 68 | n | a1 | a2 | a3 | a4 | ... +----+----+ - -+ - -+ - -+ - -+ - -+ - -+ - -+ 3. Using BOOTP to acquire mobility configuration information On receiving a BOOTP request from a client, a BOOTP server MUST return the above option in the 'vendor extensions' field, if the option has been configured in the BOOTP database (e.g. by the system administrator). A BOOTP server SHOULD also return the IPv4 subnet mask ('subnet mask' option) for the home network. The IPv4 list of default routers ('router' option)[1] is not useful for mobile home addresses; after registration with its home agent, the mobile host will use the care-of address as the address of its default router. On receiving a BOOTP reply from a server, a client uses the 32-bit (IPv4) address returned in the 'yiaddr' field as its home address, and proceeds to register that address with the associated home agent. 4. Using DHCP to acquire mobility configuration information To retrieve the above option or any other option of interest, a DHCP client MUST request the return of this information when a DHCPDISCOVER or DHCPREQUEST message is sent. This option is requested by including in a DHCPDISCOVER or DHCPREQUEST message the Perkins Expires 3 September 1995 [Page 2] Internet Draft DHCP Home Address Option 3 March 1995 'parameter request list' option containing the appropriate option codes. According to the DHCP specification, the server must return an option that is explicitly requested (assuming a value has been configured in the database). In particular, to acquire a mobile home address, a DHCP client MUST request the return of the 'mobile home address' option in a DHCPDISCOVER and DHCPREQUEST message. On receiving a BOOTP reply from a server, a client uses the 32-bit (IPv4) address returned in the 'yiaddr' field as its home address, and proceeds to register that address with the associated home agent. Perkins Expires 3 September 1995 [Page 3] Internet Draft DHCP Home Address Option 3 March 1995 5. Acknowledgements I would like to acknowledge that the form of this document was modeled after Sue Thompson's "draft-ietf-sipp-dhcpopt-01.txt". References [1] S. Alexander and R. Droms. DHCP Options and BOOTP Vendor Extensions. RFC 1533, October 1993. [2] B. Croft and J. Gilmore. Bootstrap Protocol (BOOTP). RFC 951, September 1985. [3] R. Droms. Dynamic Host Configuration Protocol. RFC 1541, October 1993. [4] IETF Mobile-IP Working Group. ietf-draft-mobileip-protocol-08.txt. Internet Draft -- work in progress, January 1995. [5] W. Wimer. Clarifications and Extensions for the Bootstrap Protocol. RFC 1542, October 1993. Author's Address Questions about this memo can be directed to: Charles Perkins Room J1-A25 T. J. Watson Research Center IBM Corporation 30 Saw Mill River Rd. Hawthorne, NY 10532 Work: +1 914 7847350 Fax: +1 914 7847007 E-mail: perk@watson.ibm.com Perkins Expires 4 September 1995 [Page 4]