HTTP/1.1 200 OK Date: Tue, 09 Apr 2002 01:51:51 GMT Server: Apache/1.3.20 (Unix) Last-Modified: Fri, 14 Mar 1997 10:01:00 GMT ETag: "2ed763-1df5-332921dc" Accept-Ranges: bytes Content-Length: 7669 Connection: close Content-Type: text/plain Internet Engineering Task Force C. Perkins INTERNET DRAFT IBM 14 March 1997 DHCP Options for Service Location Protocol draft-ietf-dhc-slp-01.txt Status of This Memo This document is a submission to the Dynamic Host Configuration Working Group of the Internet Engineering Task Force (IETF). Comments should be submitted to the dhcp@bucknell.edu 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 (North Europe), ftp.nis.garr.it (South Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). Abstract The Dynamic Host Configuration Protocol provides a framework for passing configuration information to hosts on a TCP/IP network. Entities using the Service Location Protocol need to find out the address of Directory Agents in order to transact messages. In certain other instances they may need to discover the correct scope to be used in conjunction with the service attributes and URLS which are exchanged using the Service Location Protocol. Perkins Expires 14 September 1997 [Page i] Internet Draft DHCP Options for Service Location 14 March 1997 1. Introduction The Dynamic Host Configuration Protocol [2] provides a framework for passing configuration information to hosts on a TCP/IP network. Entities using the Service Location Protocol [3] need to find out the address of Directory Agents in order to transact messages. In certain other instances they may need to discover the correct scope to be used in conjunction with the service attributes and URLs [1] which are exchanged using the Service Location Protocol. The scope MAY be denoted in any standardized character set. Values for character encoding can be found in IANA's database http://www.isi.edu/in-notes/iana/assignments/character-sets and have the values referred by the MIBEnum value. Note that each option listed below may be included multiple times in the same DHCPOFFER or DHCPREQUEST. If so, then the options SHOULD be included in order of decreasing preference. 2. Directory Agent Option This option requests or specifies a Directory Agent (DA), along with zero or more scopes supported by that DA. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Code | Length |D|S| reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | (if present) Directory Agent address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Char Encoding | scope ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Code 78 Length variable D If the 'D' bit is set, the Directory Agent address is present. S If the 'S' bit is set, the scope is present, encoded in the indicated character set. Char Encoding The standardized encoding for the characters making up the string denoting the scope. Perkins Expires 14 September 1997 [Page 1] Internet Draft DHCP Options for Service Location 14 March 1997 scope A string denoting the scope. Note that more than one Directory Agent option may be present in a DHCP message. Each such option may have the same or different scope. The client may request any Directory Agent with a particular scope, by including the Directory Agent option in a DHCP Request message with no Directory Agent address included (the 'D' bit set to zero), and the string denoting the scope. The length of the scope string is only indicated implicitly by the overall length of the option. 3. Service Scope Option This option indicates a scope that should be used by a Service Agent (SA) [3], when responding to Service Request messages as specified by the Service Location Protocol. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Code | Length | Char Encoding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | scope ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Code 79 Length variable Char Encoding The standardized encoding for the characters making up the string denoting the scope. scope A string denoting the scope. Note that more than one Service Scope option may be present in a DHCP message. The length of the scope string is only indicated implicitly by the overall length of the option. 4. Security Considerations If a malicious host is able to insert fraudulent information in DHCPOFFER packets sent to a prospective client of the Service Location Protocol, then the client will be unable to obtain service, and vulnerable to disclosing information to unauthorized service agents. Likewise, a service agent would find that it might rely on Perkins Expires 14 September 1997 [Page 2] Internet Draft DHCP Options for Service Location 14 March 1997 fraudulent or otherwise malicious directory agents to advertise its services. Many opportunities for denial of service exist. This difficulty is inherited from the much larger and more serious problem, viz. securing or authenticating any information whatsoever from a DHCP server (or client!) is not possible in common DHCP deployments. 5. Acknowledgements Thanks to Erik Guttman for his helpful suggestions in the creation of this draft. References [1] T. Berners-Lee, L. Masinter, and M. McCahill. Uniform Resource Locators (URL). RFC 1738, December 1994. [2] Ralph Droms. Dynamic Host Configuration Protocol. RFC 1541, October 1993. [3] J. Veizades, E. Guttman, C. Perkins, and S. Kaplan. Service Location Protocol, November 1996. draft-ietf-svrloc-protocol-15.txt (work in progress). Author's Address Questions about this memo can be directed to: Charles E. Perkins Sun Microsystems 2550 Garcia Avenue Mountain View, CA 94043 Phone: +1 415 336 7153 Fax: +1 415 336 0670 EMail: charliep@acm.org Perkins Expires 14 September 1997 [Page 3]