DHC L. Huang, Ed. Internet-Draft H. Deng Intended status: Informational China Mobile Expires: January 6, 2010 P. Kurapati B. Joshi Infosys Technologies July 5, 2009 Problem Statement for DHCP Relay Agent draft-huang-dhc-relay-ps-00 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. 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. This Internet-Draft will expire on January 6, 2010. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the Huang, et al. Expires January 6, 2010 [Page 1] Internet-Draft DHCP Relay PS July 2009 document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract RFC 3046 allows only the first Relay Agent to append Relay Agent Information option. In some networks, Layer 2 Relay Agents and Layer 3 Relay Agents are deployed but only Layer 2 Relay Agent appends the Relay Agent Information option. This document describes two pretty common network scenarios that uses Layer 2 and Layer 3 Relay Agents and their unique requirements where either DHCP server or Relay Agent need more information to handle DHCP messages. Huang, et al. Expires January 6, 2010 [Page 2] Internet-Draft DHCP Relay PS July 2009 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Identifying the downstream subscriber's interface . . . . . . . 4 3. location based authentication . . . . . . . . . . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 5. IANA Consideration . . . . . . . . . . . . . . . . . . . . . . 5 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 6.1. Normative References . . . . . . . . . . . . . . . . . . . 6 6.2. Informative References . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 Huang, et al. Expires January 6, 2010 [Page 3] Internet-Draft DHCP Relay PS July 2009 1. Introduction DHCP Relay Agents eliminate the necessity of having a DHCP server on each physical network. RFC 3046 introduces Relay Agent Information option which is inserted by DHCP relay agent when forwarding client- originated DHCP packets to a DHCP server. DHCP server may use the information available in this option to implement IP address or other parameter assignment policies. DHCP server echo back the Relay Agent Information option in the reply messages and Relay Agent strips this option before forwarding the reply to the client. In some network configurations, DHCP server and clients are separated by multiple Relay Agents. This document describes two such network scenarios and their unique requirements in details. This document is intended to be a problem statement document and document the problems and thier requirements. This document does not suggest any specific ways to solve these problems. 2. Identifying the downstream subscriber's interface ------- +-----------+ +-----------+ /// \\\ +------+ +------+ |Layer 2 | |Layer 3 | | | |DHCP | |Client+--+Relay Agent+--+Relay Agent+--+ Network +--+Server| +------+ +-----------+ +-----------+ | | +------+ \\\ /// ------- Figure 1: Network Scenario Under current mechanism defined in RFC3046, only downstream relay agent can insert relay agent information. In some deployments, Layer 3 Relay Agent uses unnumbered interfaces. When these Layer 3 Relay Agents are used along with Layer 2 Relay agents, they need to maintain internal states to identify the outgoing interface. Maintaining state information for each packet will not scale as number of DHCP clients increases. 3. location based authentication When IPoE is used as access authentication mechanism, clients' location is recognized through DHCP relay agent information. Sometime, operator may limit the ability of access of subscriber within the pre-arranged area, such as a certain building. But in the current deployment, relay agent information can be inserted either by the floor switches or the building switches, which means that the Huang, et al. Expires January 6, 2010 [Page 4] Internet-Draft DHCP Relay PS July 2009 subscriber!_s location is either too specific or too ambiguous. It will need much more policies for the operator to configure the subscriber's right to access from various kind of location scenario. For example, a layer 3 switch is installed for a 20 floor building and a layer 2 switch is installed at each floor inside this building. +-------+ Layer 3 |Layer 3| Relay Agent |Switch | -+---/---+--- --- / ---- -- / ---- --- / ----- +-------+ | +---/---+ | | +-------+ Layer 2 |Layer 2| | |Layer 2| | ....... | |Layer 2| Relay Agent |Switch | | |Switch | | | |Switch | +-------+ | +-------+ | | +-------+ | | | floor 1 | floor 2 | | floor 20 Figure 2: Network Scenario If the administrator plan to allow client A to access only from the first floor of this building and allow client B to access from every each floor. Based on the current mechanism, relay agent option information can only be inserted by layer 2 switch and the administrator should make 21 policies, one for client A and twenty for client B in this scenario. If Layer 3 switch can also insert some relay agent information even if layer 2 switch has inserted one, the administrator only need to make 2 policies, one for client A and the other for client B. 4. Security Considerations This is a problem statement document and does not suggest any protocol functionality. 5. IANA Consideration This document makes no requests to IANA. 6. References Huang, et al. Expires January 6, 2010 [Page 5] Internet-Draft DHCP Relay PS July 2009 6.1. Normative References [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997. [RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor Extensions", RFC 2132, March 1997. [RFC3046] Patrick, M., "DHCP Relay Agent Information Option", RFC 3046, January 2001. 6.2. Informative References [Relay Chaining] Joshi, B., "Relay Chaining in DHCPv4", draft-kurapati-dhc-relay-chaining-dhcpv4-01.txt (work in progress), June 2007. Authors' Addresses Lu Huang (editor) China Mobile 53A,Xibianmennei Ave., Xuanwu District, Beijing 100053 China Email: huanglu@chinamobile.com Hui Deng China Mobile 53A,Xibianmennei Ave., Xuanwu District, Beijing 100053 China Email: denghui02@gmail.com Huang, et al. Expires January 6, 2010 [Page 6] Internet-Draft DHCP Relay PS July 2009 Pavan Kurapati Infosys Technologies 44 Electronics City, Hosur Road Bangalore 560100 India Email: pavan_kurapati@infosys.com Bharat Joshi Infosys Technologies 44 Electronics City, Hosur Road Bangalore 560100 India Email: bharat_joshi@infosys.com Huang, et al. Expires January 6, 2010 [Page 7]