Dynamic Host Configuration WG T. Mrugalski Internet-Draft ISC Intended status: Standards Track P. Wu Expires: March 30, 2013 Tsinghua University September 26, 2012 Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Option for DHCPv4 over IPv6 Endpoint draft-mrugalski-softwire-dhcpv4-over-v6-option-01 Abstract [I-D.ietf-dhc-dhcpv4-over-ipv6] defines a way for communication between legacy DHCPv4 clients with DHCPv4 servers over IPv6-only transport. It requires deployment of Client Relay Agent (CRA) that transmits messages to IPv6-Transport Server (TSV) or IPv6-Transport Relay Agent (TRA). Deployed CRA must know an address of TSV or TRA to forward incoming client's messages. This document defines a DHCPv6 option that may be used to provision TSV or TRA location to CRAs. 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 30, 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 Mrugalski & Wu Expires March 30, 2013 [Page 1] Internet-Draft DHCPv4 over IPv6 DHCPv6 Option September 2012 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 Simplified BSD License. Table of Contents 1. Requirements Language . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. The DHCPv4-Over-IPv6 Endpoint DHCPv6 Option . . . . . . . . . . 3 4. DHCPv6 Server Behavior . . . . . . . . . . . . . . . . . . . . 4 5. DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 9.1. Normative References . . . . . . . . . . . . . . . . . . . 6 9.2. Informative References . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Mrugalski & Wu Expires March 30, 2013 [Page 2] Internet-Draft DHCPv4 over IPv6 DHCPv6 Option September 2012 1. 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 RFC 2119 [RFC2119]. 2. Introduction [I-D.ietf-dhc-dhcpv4-over-ipv6] defines a way for communication between legacy DHCPv4 clients with DHCPv4 servers (defined in [RFC2131]) over IPv6-only transport. It requires deployment of Client Relay Agent (CRA) that transmits messages to IPv6-Transport Server (TSV) or IPv6-Transport Relay Agent (TRA). Although there are several scenarios envisaged, all of them assume that CRA needs to know the recipient address of the DHCPv4-over-IPv6 traffic. In a typical deployment as [I-D.cui-softwire-b4-translated-ds-lite] or [I-D.ietf-softwire-public-4over6], CRA functionality will be a part of a Lightweight B4 element (Basic Bridging BroadBand element) implementation. Depending on the scenario discussed, the DHCPv4 over IPv6 transport endpoint could be either an IPv6-Transport Server (TSV) or an IPv6- Transport Relay Agent (TRA). Both cases are indistinguishable from CRA perspective. CRA needs to know TSV's or TRA's IPv6 address in advance to relay traffic. Again, the typical envisaged use would be the Lightweight 4over6 architecture, where TSV or TRA could be part of Lightweight AFTR implementation. As CRA uplink is IPv6-only (otherwise there would be no need to deploy DHCPv4 over IPv6), the only feasible way to provision information to CRA is over DHCPv6. Therefore this document specifies a DHCPv6 option that conveys necessary information. To provide the conveyance of the configuration information, a single DHCPv6 [RFC3315] option is used, expressing the TRA's or TSV's IPv6 address to the CRA. 3. The DHCPv4-Over-IPv6 Endpoint DHCPv6 Option The DHCPv4-over-IPv6 option is a DHCPv6 option. It consists of an option-code and option-len fields (as all DHCPv6 options have), and a fixed-length dhcpv4-over-ipv6-endpoint-addr field containing an IPv6 address that refers to the DHCPv4 over IPv6 transport endpoint to which the CRA MAY transport DHCPv4 traffic. This address represents TRA or TSV, depending on deployment scenario. Mrugalski & Wu Expires March 30, 2013 [Page 3] Internet-Draft DHCPv4 over IPv6 DHCPv6 Option September 2012 The DHCPv4-over-IPv6 option SHOULD NOT appear in any other than the following DHCPv6 messages: Solicit, Advertise, Request, Renew, Rebind, Information-Request and Reply. The format of the DHCPv4 over IPv6 option is shown in the following figure: 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 +-------------------------------+-------------------------------+ | OPTION_DHCP4_OVER_V6: (TBD) | option-len | +-------------------------------+-------------------------------+ | | | dhcpv4-over-ipv6-endpoint-addr | | | +---------------------------------------------------------------+ OPTION_DHCP4_OVER_V6: (TBD) option-len: 16 dhcpv4-over-ipv6-endpoint-addr: An IPv6 address of the DHCPv4-over-IPv6 transport endpoint. Figure 1: AFTR-Name DHCPv6 Option Format The option is validated by confirming that all of the following conditions are met: 1. the option-len is exactly 16; 2. the dhcpv4-over-ipv6-endpoint-addr contains valid unicast address. In particular any address (::), multicast (ff::/8) or IPv4-mapped IPv6 address is invalid and MUST be rejected. 4. DHCPv6 Server Behavior A DHCPv6 server SHOULD NOT send more than one DHCPv4-over-IPv6 option. It SHOULD NOT permit the configuration of multiple addresses within one DHCPv4-over-IPv6 option. Both of these conditions are handled as errors by the client, so an operator using software that does not perform these validations should be careful not to configure multiple addresses. RFC 3315 Section 17.2.2 [RFC3315] describes how a DHCPv6 client and server negotiate configuration values using the Option Request Option (OPTION_ORO). As a convenience to the reader, we mention here that a Mrugalski & Wu Expires March 30, 2013 [Page 4] Internet-Draft DHCPv4 over IPv6 DHCPv6 Option September 2012 server will not reply with a DHCPv4-over-IPv6 option if the client has not explicitly enumerated it on its Option Request Option. In other words, server SHOULD send this option only if client explicitly requested it in ORO. 5. DHCPv6 Client Behavior A client that supports the DHCPv4 over IPv6 functionality of and conforms to this specification MUST include OPTION_DHCP4_OVER_V6 on its OPTION_ORO. If the client receives the DHCPv4-over-IPv6 option, it MUST verify the option contents as described in Section 3. If the CRA entity receives more than one DHCPv4-over-IPv6 option, it MUST use only one instance of that option. If the DHCPv4-over-IPv6 option contains more than one address, the CRA entity system MUST ignore the option. It SHOULD warn its operator about such condition. Note that a CRA system may have multiple network interfaces, and these interfaces may be configured differently; some may be connected to networks that call for DHCPv4-over-IPv6, and some may be connected to networks that are using normal dual stack or other means. The CRA entity should approach this specification on an interface-by- interface basis. For example, if the CRA entity is attached to multiple networks that provide the DHCPv4-over-IPv6 option, then the CRA entity MUST configure a DHCPv4 over IPv6 transport for each interface separately as each transport provides IPv4 connectivity for each distinct interface. 6. Security Considerations This document does not present any new security issues, but as with all DHCPv6-derived configuration state, it is completely possible that the configuration is being delivered by a third party (Man In The Middle). As such, there is no basis to trust that the access the DHCPv4-over-IPv6 connection provides can be trusted. It should be protected by available security mechanisms such as IP firewalls. It should be noted that DHCPv4 over IPv6 traffic may bypass existing firewalls that are typically configured to drop incoming outside DHCPv4 over IPv4 and DHCPv6 over IPv6 traffic. RFC 3315 [RFC3315] discusses DHCPv6-related security issues. Mrugalski & Wu Expires March 30, 2013 [Page 5] Internet-Draft DHCPv4 over IPv6 DHCPv6 Option September 2012 [I-D.ietf-dhc-dhcpv4-over-ipv6] discusses DHCPv4-over-IPv6 related security issues. 7. IANA Considerations IANA is kindly requested to allocate DHCPv6 option code TBD to the OPTION_DHCP4_OVER_V6. The value should be added to the DHCPv6 option code space defined in Section 24.3 of [RFC3315]. 8. Acknowledgements Authors would like to thank nobody so far, as we have not received any comments yet. This work has been partially supported by the Polish Ministry of Science and Higher Education under the European Regional Development Fund, Grant No. POIG.01.01.02-00-045/09-00 (Future Internet Engineering Project). 9. References 9.1. Normative References [I-D.ietf-dhc-dhcpv4-over-ipv6] Cui, Y., Wu, P., Wu, J., and T. Lemon, "DHCPv4 over IPv6 Transport", draft-ietf-dhc-dhcpv4-over-ipv6-05 (work in progress), September 2012. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, 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. 9.2. Informative References [I-D.cui-softwire-b4-translated-ds-lite] Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and I. Farrer, "Lightweight 4over6: An Extension to the DS-Lite Architecture", draft-cui-softwire-b4-translated-ds-lite-08 (work in progress), September 2012. Mrugalski & Wu Expires March 30, 2013 [Page 6] Internet-Draft DHCPv4 over IPv6 DHCPv6 Option September 2012 [I-D.ietf-softwire-public-4over6] Cui, Y., Wu, J., Wu, P., Vautrin, O., and Y. Lee, "Public IPv4 over IPv6 Access Network", draft-ietf-softwire-public-4over6-03 (work in progress), August 2012. Authors' Addresses Tomasz Mrugalski Internet Systems Consortium, Inc. 950 Charter Street Redwood City, CA 94063 USA Phone: +1 650 423 1345 Email: tomasz.mrugalski@gmail.com Peng Wu Tsinghua University Beijing 100084 P.R.China Email: pengwu.thu@gmail.com Mrugalski & Wu Expires March 30, 2013 [Page 7]