DHC Working Group M. Boucadair Internet-Draft France Telecom Updates: 3315, 6422 (if approved) X. Pougnard Intended status: Standards Track Orange Labs Expires: March 15, 2013 September 11, 2012 RECONFIGURE Triggered by DHCPv6 Relay Agents draft-ietf-dhc-triggered-reconfigure-00 Abstract This document defines a new DHCPv6 message type: RECONFIGURE-REQUEST. This message is sent by a DHCPv6 relay agent to notify a DHCPv6 server about a configuration information change, so that the DHCPv6 server can send a RECONFIGURE message accordingly. This document updates RFC3315 and RFC6422. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on March 15, 2013. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. 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 Boucadair & Pougnard Expires March 15, 2013 [Page 1] Internet-Draft Relay Triggered Reconfigure September 2012 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Problem . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Requirements Language . . . . . . . . . . . . . . . . . . . 4 2. Proposed Solution . . . . . . . . . . . . . . . . . . . . . . . 4 3. RECONFIGURE-REQUEST . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Message Format . . . . . . . . . . . . . . . . . . . . . . 5 3.2. Message Validation . . . . . . . . . . . . . . . . . . . . 5 3.3. Creation and Transmission of RECONFIGURE-REQUEST . . . . . 6 3.4. Server Behaviour . . . . . . . . . . . . . . . . . . . . . 7 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7.1. Normative References . . . . . . . . . . . . . . . . . . . 8 7.2. Informative References . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 Boucadair & Pougnard Expires March 15, 2013 [Page 2] Internet-Draft Relay Triggered Reconfigure September 2012 1. Introduction 1.1. Problem [RFC6422] updates the DHCPv6 specification [RFC3315] with a new feature to let a DHCPv6 relay agent communicate information towards a DHCPv6 Client, and which is not available at the DHCPv6 server. This is achieved owing to the use of RSOO (Relay-Supplied Options option) which carries configuration data to the DHCPv6 server. The data conveyed in an RSOO is then sent back by the DHCPv6 server to the requesting DHCPv6 client. An example of a RSOO context is shown in Figure 1; only a subset of exchanged DHCPv6 and RADIUS messages is represented. +-------+ +-------+ +-------+ |DHCPv6 | | NAS | |Radius | |Client | |(DHCPv6| |Server | | | | Relay)| | | +-------+ +-------+ +-------+ | | | |---Solicit---------------->| | | |---Access-Request---------->| |<--Access-Accept------------| | (e.g. DS-Lite-Tunnel-Name)| .... | +-------+ | |DHCPv6 | | |Server | | | | | +-------+ | | |---Relay-Forward----------->| | (RSOO(DS-Lite-Tunnel-Name))| | | | |<--Relay-Reply--------------| |<--Advertise---------------| | (e.g., OPTION_AFTR_NAME) | .... Figure 1: An Example of the RSOO Option Usage The change of the configuration may result in RADIUS exchanges ([RFC5176]) between the NAS/DHCPv6 relay agent and Dynamic Authorization Client (DAC) server as shown in Figure 2. Note the change of the configuration in the DHCPv6 relay agent can be Boucadair & Pougnard Expires March 15, 2013 [Page 3] Internet-Draft Relay Triggered Reconfigure September 2012 triggered by any other out-of-band mechanism. +-------+ +-------+ +-------+ |DHCPv6 | | NAS | |Radius | |Client | |(DHCPv6| |Server/| | | | Relay)| | DAC | +-------+ +-------+ +-------+ | | | |<-----CoA-Request-----------| | (e.g. DS-Lite-Tunnel-Name) | |------CoA-Response--------->| .... CoA (Change-of-Authorization, [RFC5176]) Figure 2: Change of configuration Whenever the configuration information sent by the DHCPv6 relay agent to the DHCPv6 server change, the DHCPv6 server has no means to detect it so that it can send a Reconfigure message with the updated configuration data accordingly. A solution is sketched in Section 2. 1.2. Requirements Language 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 [RFC2119]. 2. Proposed Solution To solve the problem described in Section 1.1, this document proposes a new DHCP message called Reconfigure-Request. In the example depicted in Figure 3 a Reconfigure-Request message is sent by the DHCPv6 relay agent to a DHCPv6 server as soon as the configuration data conveyed in an RSOO option have changed. Upon receipt of this message, and if it is configured to support such mode, the DHCPv6 server must build a Reconfigure message. This message is then sent to the DHCPv6 relay, which in turn will forward the message to the appropriate DHCPv6 client. This setup assumes the relay has a record of the client, so that it has enough information to send the Reconfigure-Request message to the server. Means to recover state in failure events must be supported, but are not discussed in this document. Boucadair & Pougnard Expires March 15, 2013 [Page 4] Internet-Draft Relay Triggered Reconfigure September 2012 +-------+ +-------+ +-------+ |DHCPv6 | | NAS | |Radius | |Client | |(DHCPv6| |Server/| | | | Relay)| | DAC | +-------+ +-------+ +-------+ | | | |<-----CoA-Request-----------| | (e.g. DS-Lite-Tunnel-Name) | | | |------CoA-Response--------->| .... | +-------+ | |DHCPv6 | | |Server | | | | | +-------+ | | |---Reconfigure-Request----->| | | | | | |<--Relay-Reply -------------| |<--Reconfigure-------------| (Reconfigure) | | | | .... Figure 3: RECONFIGURE-REQUEST Flow Example The Reconfigure-Request message can also be used in other scenarios than those that assume the use of RSOO. It is out of scope of this document to describe all these scenarios. 3. RECONFIGURE-REQUEST 3.1. Message Format A new message type code is defined: RECONFIGURE-REQUEST (To be assigned by IANA, see Section 4). RECONFIGURE-REQUEST uses the same format as defined in Section 6 of [RFC3315]. 3.2. Message Validation Clients MUST silently discard any received RECONFIGURE-REQUEST messages. Boucadair & Pougnard Expires March 15, 2013 [Page 5] Internet-Draft Relay Triggered Reconfigure September 2012 Servers MUST silently discard any received RECONFIGURE-REQUEST messages that meet any of the following conditions: o the message does not include an OPTION_CLIENTID option. o the message includes an OPTION_SERVERID option but the contents of the OPTION_SERVERID option does not match the server's identifier. The server MUST be configurable to accept or reject RECONFIGURE- REQUEST messages. If the server is configured to reject RECONFIGURE- REQUEST, the server MUST silently discard any RECONFIGURE-REQUEST it receives. Discussion Note: Should the document specify the behavior of intermediate relay agents if any? Because this message provides a mechanism for triggering the DHCP Reconfigure message, and the DHCP Reconfigure message can raise security threats (e.g., to control the timing of a DHCP renewal), the DHCP server MUST have some mechanism for determining that the relay agent is a trusted entity. RECONFIGURE-REQUEST messages originating from unknown relay agents MUST be silently dropped. 3.3. Creation and Transmission of RECONFIGURE-REQUEST For any event (e.g., modification of the configuration information) that requires the server to issue a Reconfigure message, the relay agent determines the client which is affected by the change and then builds a Reconfigure-Request message: the relay agent sets the "msg- type" field to RECONFIGURE-REQUEST and sets the "transaction-id " field to 0. The relay agent MUST include an OPTION_CLIENTID option [RFC3315] so that the DHCPv6 server can identify the corresponding client. The relay agent MAY supply the updated configuration in the RSOO [RFC6422]. The relay agent MAY supply an OPTION_RECONF_MSG option to indicate which form of Reconfigure to use. When several clients are concerned with a configuration change, the relay MUST include several OPTION_CLIENTID options, each of them identifies a specific client. If including OPTION_CLIENTID options of all impacted clients exceeds the maximum message size, the relay MUST generate several RECONFIGURE-REQUEST messages required to carry all OPTION_CLIENTID options. Discussion Note: What to do when all clients bound to the same relay agent are impacted by a configuration change? Should the document indicate the relay MUST include Relay-ID Option (RFC5460)? Boucadair & Pougnard Expires March 15, 2013 [Page 6] Internet-Draft Relay Triggered Reconfigure September 2012 3.4. Server Behaviour Upon receipt of a valid Reconfigure-Request message from a DHCPv6 relay agent (see Section 3.2), the server determines the client(s) for which a Reconfigure message is to be sent. The server MAY use the content of the OPTION_RECONF_MSG option supplied by the relay agent to determine which form of Reconfigure to use. If RSOO is supplied, the server MAY use its content to double check whether a Reconfigure is required to be sent to the client. This assumes the server store the content of RSOO it used to generate configuration data sent to requesting clients. Then, the server MUST follow the procedure defined in Section 19.1 of [RFC3315] to construct a Reconfigure message. This message may be sent directly to the DHCPv6 client or to a relay agent [RFC3315]. 4. IANA Considerations This document requests IANA to assign a new DHCPv6 Message type: RECONFIGURE-REQUEST 5. Security Considerations Security considerations elaborated in [RFC3315] and [RFC6422] must be taken into account. In addition, DHCPv6 servers MAY be configured to discard relayed RECONFIGURE-REQUEST messages or restrict relay chaining (see [RFC5007] for more discussion about the rationale of this recommended behavior). Relay agents SHOULD implement appropriate means to prevent using RECONFIGURE-REQUEST messages as a denial-of-service attack on the DHCPv6 servers. 6. Acknowledgements Many thanks to T. Lemon, R. Maglione, A. Kostur, G. Halwasia and C. Jacquenet for the comments and review. 7. References Boucadair & Pougnard Expires March 15, 2013 [Page 7] Internet-Draft Relay Triggered Reconfigure September 2012 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. [RFC6422] Lemon, T. and Q. Wu, "Relay-Supplied DHCP Options", RFC 6422, December 2011. 7.2. Informative References [RFC5007] Brzozowski, J., Kinnear, K., Volz, B., and S. Zeng, "DHCPv6 Leasequery", RFC 5007, September 2007. [RFC5176] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B. Aboba, "Dynamic Authorization Extensions to Remote Authentication Dial In User Service (RADIUS)", RFC 5176, January 2008. Authors' Addresses Mohamed Boucadair France Telecom Rennes, 35000 France Email: mohamed.boucadair@orange.com Xavier Pougnard Orange Labs Lannion, France Phone: Email: xavier.pougnard@orange.com Boucadair & Pougnard Expires March 15, 2013 [Page 8]