Internet Engineering Task Force B. Patel INTERNET DRAFT C. Perkins IBM Research 09 February 1996 The Mobility Agent Configuration Option to PPP IP Control Protocol (IPCP) draft-patel-mobileip-pppext-00.txt Status of This Memo This document is a submission to the Mobile-IP Working Group of the Internet Engineering Task Force (IETF). Comments should be submitted to the mobile-ip@smallworks.com 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 inappropriate to use Internet-Drafts as reference material or to cite them other than as ``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 ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). Abstract This document specifies a new option to the IP Control Protocol (IPCP) which can be used by mobile nodes to allow more efficient use of PPP along with the mobile-IP protocol. The new option allows the mobile IP peers to negotiate the use of mobile IP protocol over a PPP link. This option allows a requesting peer to determine if the responding peer is capable of and willing to perform either home or foreign agent functions of mobile IP. As part of this transaction, the requesting peer provides its own IP address to the responding peer and requests a care-of address from the responding peer. Patel, Perkins Expires 09 August 1996 [Page i] Internet Draft Mobility Agent Option to IPCP 09 February 1996 1. Introduction Mobile-IP [1] allows mobile nodes to move from one point of attachment within the Internet to another, and defines mechanisms by which a home agent on the mobile node's home network can send packets to the mobile node. PPP [3] offers a popular means by which mobile nodes may attach to the Internet, often by creation of links using telephone hookups. Mobile-IP requires that the mobile node acquire a care-of address at every new point of attachment when it is away from its home network. In this document, a mobility agent is defined to be either a home agent or a foreign agent, as those terms are defined in [1]. There are two ways in which a mobile IP host might communicate with the rest of the network as a dial-in client over a PPP link. 1. The mobile node could be able to decapsulate datagrams sent to its care-of address, and 2. The dial-in server could be capable of being the foreign or home agent for the mobile IP peer. If, as in (1), the mobile IP host is capable of assigning a new care-of address to one of its interfaces and decapsulating datagrams sent to that care-of address, it could obtain an address through the IP Address option of IPCP and use that as care-of address. No changes are required in IPCP for this mode of operation. However, if as in (2) the mobile IP host cannot, or does not choose to, decapsulate datagrams sent to its care-of address, it must determine whether its peer (e.g., the dial-in server) is capable of serving as a home or foreign agent for the mobile node. In order to do that, the mobile IP host will use the Mobility Agent Configuration option proposed in this document to notify the server of its home address. The responding peer will indicate if it can act as a home agent or as a foreign agent for the mobile node. In the latter case, it will also provide a care-of address to the mobile node. This document specifies an option to IPCP [2, 3], which is an integral part of the PPP protocol suite, to allow the mobile node determine if its peer is a mobility agent, and possibly to obtain a care-of address useful with the mobile-IP protocol, when it negotiates with a PPP peer. Patel, Perkins Expires 09 August 1996 [Page 1] Internet Draft Mobility Agent Option to IPCP 09 February 1996 2. The Mobility Agent Configuration Option to IPCP This configuration option enables a mobile node to negotiate with a peer which is capable of being mobility agent. When a peer receives the Mobility Agent Configuration option with a valid IP address, it MUST respond in one of the following ways: a. Configure-Ack with its own IP address, meaning that the requesting peer is connected to its home subnet, and that the responding peer can act as a home agent. After the link is established, the responding peer MUST send a Mobile-IP Agent Advertisement, possibly in response to a Mobile-IP Agent Solicitation. b. Configure-Nak with a care-of address, meaning that the mobile node is not connected to its home subnet. However, the responding peer is capable of and is willing to act as a foreign agent for the requesting peer. The care-of address to be used by the requesting peer is included in the response. After the link is established, the responding peer MUST send a Mobile-IP Agent Advertisement, possibly in response to a Mobile-IP Agent Solicitation. c. Configure-Rej to indicate that the responding peer is not capable of being a mobile IP foreign/home agent or it does not implement this option. The requesting peer may send requests with IP Address and the Mobility Agent Configuration options at the same time. However, if the Mobility Agent Configuration option is supported by the responding peer, the requesting peer may not need to use the IP address obtained using the IP Address option. Therefore, it is recommended that a mobile IP peer first try the Mobility Agent Configuration option and then the IP Address option, if necessary. Patel, Perkins Expires 09 August 1996 [Page 2] Internet Draft Mobility Agent Option to IPCP 09 February 1996 3. Format of the Mobility Agent Configuration Option The format of the Mobility Agent Configuration Option 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | IP Address ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... IP Address (cont) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type 4 Length 6 IP Address The four octet IP Address is the home address of the mobile node which sends the Mobility Agent Configuration option. 4. Security Considerations Security considerations are not addressed in this document. References [1] IETF Mobile-IP Working Group. IPv4 Mobility Support. ietf-draft-mobileip-protocol-12.txt - work in progress, September 1995. [2] G. McGregor. The PPP Internet Procotol Control Protocol (IPCP). RFC 1332, May 1992. [3] G. McGregor and G. S. Pall. draft-ietf-pppext-ipcp-network-00.txt. Internet Draft -- work in progress, October 1995. Patel, Perkins Expires 09 August 1996 [Page 3] Internet Draft Mobility Agent Option to IPCP 09 February 1996 Authors' Addresses Questions about this memo can also be directed to: Baiju Patel Room H3-D36 T. J. Watson Research Center IBM Corporation 30 Saw Mill River Rd. Hawthorne, NY 10532 Work: +1-914-784-6786 Fax: +1-914-784-6205 E-mail: baiju@watson.ibm.com Charles Perkins Room H3-D34 T. J. Watson Research Center IBM Corporation 30 Saw Mill River Rd. Hawthorne, NY 10532 Work: +1-914-784-7350 Fax: +1-914-784-6205 E-mail: perk@watson.ibm.com Patel, Perkins Expires 09 August 1996 [Page 4]