Internet Engineering Task Force Richard Johnson Internet Draft Mark Stapp Expiration: October 2004 Theyn Palaniappan File: draft-ietf-dhc-subscriber-id-03.txt Cisco Systems, Inc. DHCP Subscriber ID Suboption for the DHCP Relay Agent Option October 15, 2004 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Copyright Notice Copyright (C) The Internet Society (2002). All Rights Reserved. Abstract This memo defines a new DHCP Relay Suboption for passing a printable character string defining named the "Subscriber ID". Its intended purpose is to provide an unchanging description of a "subscriber" such that the underlying hardware and/or aggregation point for a particular DHCP client may change without having to change the configuration on the DHCP server itself. Johnson, et. al. [Page 1] Internet Draft DHCP Subscriber ID Suboption October 2004 1.0 Introduction The Remote-ID sub-option of the relay agent information option (also called option-82) are calculated based on network resources like IP address of the NSAP, atm VP, atm VC. As a result, when moving a link to a different port, a different value is calculated. This holds true for every subscriber that is connected with the particular link and the links may connected to different service providers. In a situation where the connection to the customer is provided separately from the DHCP service, when the subscriber moves, each Service Provider must be informed of the change and all the Service Providers have to change their DHCP [2] settings for the affected customers. This results in delays and complications due to necessary synchronization of the changes between all parties involved. When the service delivered to the customer has not changed, every move involves administrative changes in Service Providers environment causing delay in the customer service. Any change in the underlying hardware connecting to the customer site will involve reconfiguration of the Service Provider's DHCP server. From an administrative viewpoint there is a simple need to connect a customer's DHCP configuration with the customer administrative information. Using a "subscriber-id" character string, which can uniquely identify the customer, would be preferable to maintaining a database relating the customer to their Option 82 information. Furthermore, any such database would need to be constantly updated whenever a customer moves or the hardware is changed, while the "subscriber-id" designating the customer will not change. An additional Relay Suboption for the DHCP Relay Agent option is being introduced, to add a configurable printable character string to provide this customer information. This unique id will enable the Service Provider to identify a subscriber and to assign/activate subscriber specific actions, e.g. assignment of host IP address, subnet mask, DNS, trigger accounting, etc. This specific field is de- coupled from the NAS-IP, since the users could be able to move between NAS termination points. Thus when a subscriber moves from one NAS to another, this would not result in a configuration change on the side of the DHCP server of the Service Provider. This memo describes a new DHCP Relay suboption which would carry a "Subscriber ID" value. The value is a printable character string giving the name of the subscriber. Johnson, et. al. [Page 2] Internet Draft DHCP Subscriber ID Suboption October 2004 1.1 Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC-2119 [1]. 1.2 Terminology VC Virtual Channel. Logical circuit created to ensure reliable communication between two network devices. A virtual circuit is defined by a VPI/VCI pair, and can be either permanent (PVC) or switched (SVC). Virtual circuits are used in Frame Relay and X.25. In ATM, a virtual circuit is called a virtual channel. VP Virtual Path. Logical grouping of virtual circuits that connect two sites. NAS Network Access Server. Platform (or collection of platforms) that interfaces between the packet world (for example, the Internet) and the circuit world (for example, the PSTN). NSAP Network Service Access Point. Network addresses, as specified by ISO. An NSAP is the point at which OSI network service is made available to a transport layer (Layer 4) entity. PSTN Public Switched Telephone Network. General term referring to the variety of telephone networks and services in place worldwide. NVT ASCII Network Virtual Terminal American Standard Code for Information Interchange. [6] 2.0 DHCP Relay Information Suboption Definition The Subscriber ID is a DHCP Relay Information Suboption. The exact option code value is TBD. The suboption takes the same form as other Relay Information Suboptions: Code Len Subscriber ID string +-----+-----+------+-----+-----+--- | TBD | n | v1 | v2 | v3 | ... +-----+-----+------+-----+-----+--- Johnson, et. al. [Page 3] Internet Draft DHCP Subscriber ID Suboption October 2004 The option minimum length (n) is 1. The "Subscriber ID string", in NVT ASCII, MUST NOT be NULL terminated since the length is specified in the "len" field. This option provides the DHCP server additional information to the DHCP server. The DHCP server, if it is configured to support this option, should use this information in addition to other options included in the DHCPDISCOVER packet in order to assign an IP address and/or other configuration parameters for the DHCP client. As per [3], the contents of the entire Relay Agent Option SHALL be included in all replies by DHCP servers understanding the Relay Agent Option. There is no special additional processing for this suboption. 3.0 Security Considerations Message authentication in DHCP for intradomain use where the out-of- band exchange of a shared secret is feasible is defined in RFC 3118 [5]. Potential exposures to attack are discussed in section 7 of the DHCP protocol specification in RFC 2131 [2]. The DHCP Relay Agent option depends on a trusted relationship between the DHCP relay agent and the server, as described in section 5 of RFC 3046. While the introduction of fraudulent relay-agent options can be prevented by a perimeter defense that blocks these options unless the relay agent is trusted, a deeper defense using the authentication option for relay agent options [4] SHOULD be deployed as well. 4.0 IANA Considerations IANA has assigned a value of TBD for the DHCP Relay Information Suboption code described in this document. 5.0 Acknowledgments This document is the result of work done within Cisco Systems. Thanks to Mark Stapp and Theyn Palaniappan for their work on this option definition and the other related work for which this is necessary. Thanks also to Andy Sudduth for his review comments. References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, BCP 14, March 1997. Johnson, et. al. [Page 4] Internet Draft DHCP Subscriber ID Suboption October 2004 [2] Droms, R. "Dynamic Host Configuration Protocol", RFC 2131, March 1997. [3] Patrick, M., "DHCP Relay Agent Information Option", RFC 3046, January 2001 [4] Stapp, M. "The Authentication Suboption for the DHCP Relay Agent Option", draft-ietf-dhc-auth-suboption-00.txt, June 23, 2002 [5] Droms, R. "Authentication for DHCP Messages", RFC 3118, June 2001 [6] Postel, J., "Telnet Protocol Specification", RFC 854, May 1983 Author Information: Richard Johnson Theyn Palaniappan Cisco Systems 170 W. Tasman Dr. San Jose, CA 95134 Phone: (408) 526-4000 EMail: athenmoz@cisco.com raj@cisco.com Mark Stapp Cisco Systems 250 Apollo Drive Chelmsford, MA 01824 Phone: (978) 244-8000 EMail: rdroms@cisco.com mjs@cisco.com Copyright Notice Copyright (C) The Internet Society (2002). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published Johnson, et. al. [Page 5] Internet Draft DHCP Subscriber ID Suboption October 2004 and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS 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." Johnson, et. al. [Page 6]