Network Working Group Walter D. Lazear INTERNET DRAFT MITRE Corporation January 1998 Expires July 1998 The Autonomous System Option for DHCP Status of this memo 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). 1. Abstract This document describes a configuration option that may be used by hosts acting as IP forwarders. The option contains information about the autonomous system in which the host resides and may be required by routing protocols. 2 Requirements Throughout this document, the words that are used to define the significance of particular requirements are capitalized. These words are: o "MUST" This word or the adjective "REQUIRED" means that the item is an absolute requirement of this specification. o "MUST NOT" This phrase means that the item is an absolute prohibition of this specification. o "SHOULD" This word or the adjective "RECOMMENDED" means that there may exist valid reasons in particular circumstances to ignore this item, but the full implications should be understood and the case carefully weighed before choosing a different course. Lazear [Page 1] The Autonomous System Option for DHCP January 1998 o "SHOULD NOT" This phrase means that there may exist valid reasons in particular circumstances when the listed behavior is acceptable or even useful, but the full implications should be understood and the case carefully weighed before implementing any behavior described with this label. o "MAY" This word or the adjective "OPTIONAL" means that this item is truly optional. One vendor may choose to include the item because a particular marketplace requires it or because it enhances the product, for example; another vendor may omit the same item. 3 Terminology This document uses the following terms: o "DHCP client" A DHCP client is an Internet host using DHCP to obtain configuration parameters such as a network address. o "DHCP server" A DHCP server is an Internet host that returns configuration parameters to DHCP clients. 4 Autonomous System Option Any client that is configured by DHCP [1] may act as an IP packet forwarder. This role as router may be performed at the edge of an administrative routing domain known as an autonomous system (AS). The AS is identified by a 16-bit AS number. At an AS edge, a routing protocol may be required to exchange routing information with other AS routers (the Border Gateway Protocol [3] is an example of such a routing protocol). These routing protocols may require that the client know the number of the AS in which it resides. This option is used by DHCP servers to provide the autonomous system number of the local network. The DHCP client can obtain this parameter as part of the normal DHCP protocol message exchange or separately via DHCPINFORM. Code Len AS Number +-----+-----+-----+-----+ | 109 | 2 | a1 | a2 | +-----+-----+-----+-----+ The code for this option is 109 and the length is 2. Lazear [Page 4] The Autonomous System Option for DHCP January 1998 5 References [1] Droms, R., "Dynamic Host Configuration Protocol", RFC 1541, Bucknell University, October 1993. [2] Alexander, S., and R. Droms, "DHCP Options and BOOTP Vendor Extensions", RFC 1533, Lachman Technology, Inc., Bucknell University, October 1993. [3] Rekhter, Y., and T. Li. "A Border Gateway Protocol 4 (BGP-4)", RFC 1771, IBM Corp., Cisco Systems, March 1995. 5 Author's Address Walter D. Lazear MITRE Corporation 1820 Dolley Madison Blvd. McLean VA 22102 Phone: 703 883 6515 EMail: lazear@mitre.org This document will expire on July, 1998 Lazear [Page 5]