DHC Working Group L. Huang Internet-Draft H. Deng Intended status: Informational China Mobile Expires: September 5, 2010 March 4, 2010 DHCP option including Multiple Relay Agents' Information draft-huang-dhc-multiple-relay-agents-option-01 Abstract RFC 3046 allows only the first Relay Agent to append Relay Agent Information option. In some networks, both Layer 2 Relay Agents and Layer 3 Relay Agents are deployed and their information is necessary for DHCP packets forwarding and DHCP server's policy designing described as [I-D.huang-dhc-relay-ps]. This document defines new sub-options for Relay Agent Information option (option 82) and describes how multiple relay agents add their information into option 82. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. 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 September 5, 2010. Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. Huang & Deng Expires September 5, 2010 [Page 1] Internet-Draft Option including Multiple Agents' Info March 2010 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. DHCP option including Multiple Relay Agents' Information . . . 4 2.1. Format . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 5. Informative References . . . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 Huang & Deng Expires September 5, 2010 [Page 2] Internet-Draft Option including Multiple Agents' Info March 2010 1. Introduction As defined in RFC 3046, Relay Agent Information option is inserted by the DHCP relay agent (or downstream network element) when forwarding client-originated DHCP packets to a DHCP server. Servers recognizing the Relay Agent Information option may use the information to implement IP address or other parameter assignment policies. The DHCP Server echoes the option back to the relay agent in server-to- client replies, and the relay agent strips the option before forwarding the reply to the client. RFC 3046 allows only one agent add its information with option 82. But in some scenarios as [I-D.huang-dhc-relay-ps], multiply relay agents need to insert more information into the same DHCP message. This document defines new sub-options for Relay Agent Information option (option 82) and describes how multiple relay agents add their information into option 82. Huang & Deng Expires September 5, 2010 [Page 3] Internet-Draft Option including Multiple Agents' Info March 2010 2. DHCP option including Multiple Relay Agents' Information 2.1. Format +-------+-----+-----+ |Code(x)| Len |Value| +-------+-----+-----+ Sub-option x: Agent ID. Describe a unique identifier for the agent who insert this set of sub-options. +-------+-------+ |Code(y)| Len(0)| +-------+-------+ Sub-option y: Identify the end of information of one device. 2.2. Mechanism ------- +-----------+ +-----------+ /// \\\ +------+ +------+ |Layer 2 | |Layer 3 | | | |DHCP | |Client+--+Relay Agent+--+Relay Agent+--+ Network +--+Server| +------+ +-----------+ +-----------+ | | +------+ \\\ /// ------- As shown in above figure, it's a most popular network scenario where option including Multiple Relay Agents' Information is necessary. Based on the demand as [I-D.huang-dhc-relay-ps], agents work as following: (1) An initiating client sends a DHCP discovery packet. (2) Layer 2 relay agent receives the discovery packet without option 82. So it inserts an option 82 as [RFC3046]. After that, the discovery packet is forwarded to the appropriate port. (3) Layer 3 relay agent receives the discovery packet and check out that it already contains an option 82. Firstly it adds an sub-option y defined in section 2.2 into the existing option 82 following sub- options added by layer 2 agent. And then it adds its agent ID sub- option(x), circuit ID sub-option and end ID sub-option(y) into the existing option 82. After that, the discovery packet is forwarded and reaches DHCP server directly or through a network. (4) DHCP server handles the discovery packet and could carry out flexible IP assigning or other policies based on the information of Huang & Deng Expires September 5, 2010 [Page 4] Internet-Draft Option including Multiple Agents' Info March 2010 option 82 described in this document. After that DHCP server reply a DHCP response packet containing the original option 82 carried in the corresponding discovery packet. (5) Layer 3 relay agents quickly get the right outgoing interface based on the information in the option 82 and forward the response packet after deleting sub-options it added before. (6) Layer 2 relay agents quickly get the right outgoing interface based on the information in the option 82 and forward the response packet. Layer 2 relay agent deletes the whole option 82 before forwarding the packet. If there are more relay agents between Layer 2 and Layer 3 relay agent or between Layer 3 relay agent and DHCP server, the third and the following relay agents could only add their agent ID sub- option(x), circuit ID sub-option and end ID sub-option(y) into the existing option 82 before forwarding the discovery packet upward. The processing of replay packet from DHCP server to client is similar as above. Huang & Deng Expires September 5, 2010 [Page 5] Internet-Draft Option including Multiple Agents' Info March 2010 3. Security Considerations This document doesn't propose any new protocol. Huang & Deng Expires September 5, 2010 [Page 6] Internet-Draft Option including Multiple Agents' Info March 2010 4. IANA Considerations This document requires new numbers for sub-option code x and y described in section 2.1. Huang & Deng Expires September 5, 2010 [Page 7] Internet-Draft Option including Multiple Agents' Info March 2010 5. Informative References [I-D.huang-dhc-relay-ps] Huang, L., Deng, H., Kurapati, P., and B. Joshi, "Problem Statement for DHCP Relay Agent", draft-huang-dhc-relay-ps-00 (work in progress), July 2009. [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. Huang & Deng Expires September 5, 2010 [Page 8] Internet-Draft Option including Multiple Agents' Info March 2010 Authors' Addresses Lu Huang China Mobile Unit2, 28 Xuanwumenxi Ave,Xuanwu District Beijing 100053 China Email: huanglu@chinamobile.com Hui Deng China Mobile Unit2, 28 Xuanwumenxi Ave,Xuanwu District Beijing 100053 China Email: denghui@chinamobile.com Huang & Deng Expires September 5, 2010 [Page 9]