Network Working Group S. Krishnan Internet-Draft Ericsson Intended status: Standards Track November 11, 2007 Expires: May 14, 2008 Carrying DHCP options over Neighbor Discovery Messages draft-krishnan-intarea-ra-dhcp-00 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of 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 May 14, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Krishnan Expires May 14, 2008 [Page 1] Internet-Draft Carrying DHCP Options over ND messages November 2007 Abstract DHCP options are used to convey network and host configuration information to the hosts attached to a network. Some networks may wish to configure their routers to advertise these same pieces of information, and might use IPv6 Router Advertisements do distribute these parameters. This document defines a generic neighbor discovery option for carrying DHCP options. This option is carried over IPv6 Router Advertisements. Table of Contents 1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Justification . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 6 5. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6. DHCP Container(DHCPC) Option . . . . . . . . . . . . . . . . . 8 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8. Security Considerations . . . . . . . . . . . . . . . . . . . 11 9. Acknowledgmentes . . . . . . . . . . . . . . . . . . . . . . . 12 10. Normative References . . . . . . . . . . . . . . . . . . . . . 13 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14 Intellectual Property and Copyright Statements . . . . . . . . . . 15 Krishnan Expires May 14, 2008 [Page 2] Internet-Draft Carrying DHCP Options over ND messages November 2007 1. Requirements notation 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]. Krishnan Expires May 14, 2008 [Page 3] Internet-Draft Carrying DHCP Options over ND messages November 2007 2. Introduction Router Advertisements (RAs) as defined in [RFC2461] are used to deliver configuration information that is common to several nodes in the same network. The router advertisements are usually multicasted to all nodes in a given network in order to be scalable. The configuration information is contained in Neigbor Discovery (ND) options. DHCP [RFC3315] is used for delivering addressing information and other related configuration information to single clients when they request it. Since there are two mechanisms for delivering common configuration information to a given node, configuration parameters need to be defined under two varying option formats. This leads to duplication of work needed to standardize these options and additional implementation complexity on hosts in order to process these option variants. In order to prevent this duplication, this document proposes a neighbor discovery option that can be used to directly carry any relevant DHCP option. Krishnan Expires May 14, 2008 [Page 4] Internet-Draft Carrying DHCP Options over ND messages November 2007 3. Justification Recently there has been interest in doing more of DHCP work using Neighbor Discovery (Router Advertisement) messages. This is mainly to accomodate environments where DHCP is not available and the only way of convey configuration information is through RAs. Since DHCP options cannot be carried in RAs this leads to duplicate standardization efforts to develop ND options for options already developed for DHCP. For example consider [RFC5006] that redefines a DNS server address option for RAs that has been defined long ago for DHCP. Not only does this waste valuable time in redundant standardization effort, it also complicates client implementations that need to be able to parse and understand tho incompatible option formats. It also takes away valuable code points away from the neighbor discovery message types (8 bit value). Thus it make sense to define a DHCP carrier option for neighbor discovery messages so that we can reuse DHCP options as necessary without coming up with new neighbor discovery options. Krishnan Expires May 14, 2008 [Page 5] Internet-Draft Carrying DHCP Options over ND messages November 2007 4. Applicability It is possible to carry any DHCP option using the DHCPC option. However, this does not always make sense since there are DHCP options that are client specific and hence are not uniform across all the hosts in the network. The DHCPC option SHOULD NOT be used to carry DHCP options that are client specific. This option can be carried in any neighbor discovery messages. Krishnan Expires May 14, 2008 [Page 6] Internet-Draft Carrying DHCP Options over ND messages November 2007 5. Operation After a node receives a neighbor discovery that contains a DHCPC option it needs to verify if the DHCPC option length is at least 1 (8 octets). If it is not, the node MUST NOT process the DHCPC option any further and SHOULD log an error message locally. Otherwise it needs to process the embedded DHCP options one at a time as it would if it had received them through a DHCP message. It is entirely possible that the code for processing these options is shared between the neighbor discovery based delivery and DHCP based delivery of these options. Krishnan Expires May 14, 2008 [Page 7] Internet-Draft Carrying DHCP Options over ND messages November 2007 6. DHCP Container(DHCPC) Option The DHCPC option in Neighbor Discovery messages is used to carry complete DHCP options. There can be more than DHCP option contained in a DHCPC option. The number of contained DHCP options is not explicitly mentioned in the DHCPC. The receiving node MUST process all the contained options 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPT1_code | OPT1_len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPT1_data | | (OPT1_len octets) | . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPTn_code | OPTn_len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPTn_data | | (OPTn_len octets) | . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type 8-bit identifier of the type of option. The option identifier for the DHCPC option will be allocated by the IANA. Option Length 8-bit unsigned integer. The length of the option (including the type and length fields) in units of 8 octets. The value 0 is considered invalid. OPT1_code 16-bit unsigned integer. The DHCPv6 option code of the first DHCP option that is carried in the DHCPC option. OPT1_len 16-bit unsigned integer. The length of the option data of the first included DHCP option (excluding the OPT1_code and the Krishnan Expires May 14, 2008 [Page 8] Internet-Draft Carrying DHCP Options over ND messages November 2007 OPT1_len fields) OPT1_Data The data field of the first included neighbor discovery option. The contents of this field are determined by the type of the option. OPT1_code 16-bit unsigned integer. The DHCPv6 option code of the first DHCP option that is carried in the DHCPC option. OPT1_len 16-bit unsigned integer. The length of the option data of the first included DHCP option (excluding the OPT1_code and the OPT1_len fields) OPT1_Data The data field of the first included neighbor discovery option. The contents of this field are determined by the type of the option. Figure 1: DHCPC layout Krishnan Expires May 14, 2008 [Page 9] Internet-Draft Carrying DHCP Options over ND messages November 2007 7. IANA Considerations This document defines a new IPv6 neighbor discovery option for carrying DHCP options. IANA is requested to assign the a new neighbor discovery option type in the registry maintained at http://www.iana.org/assignments/icmpv6-parameters DHCP Carrier Option [RFC-krishnan-intarea-ra-dhcp-00.txt] The option type 26 is recommended as it is the first unused option type at the time of writing this draft. Krishnan Expires May 14, 2008 [Page 10] Internet-Draft Carrying DHCP Options over ND messages November 2007 8. Security Considerations The mechanism described in this document provides a method by which one or more DHCP options can be carried using IPv6 Router Advertisement messages. The neighbor discovery messages containing the DHCPC option may be intercepted, modified or replayed in order to communicate false configuration data to the client hosts. In order to prevent these kinds of attacks, it is recommended that SEND [RFC3971] be used. Krishnan Expires May 14, 2008 [Page 11] Internet-Draft Carrying DHCP Options over ND messages November 2007 9. Acknowledgmentes The author would like to thank Jari Arkko for his detailed review and comments on the earlier versions of this document. Krishnan Expires May 14, 2008 [Page 12] Internet-Draft Carrying DHCP Options over ND messages November 2007 10. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2461] Narten, T., Nordmark, E., and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998. [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. [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005. [RFC5006] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli, "IPv6 Router Advertisement Option for DNS Configuration", RFC 5006, September 2007. Krishnan Expires May 14, 2008 [Page 13] Internet-Draft Carrying DHCP Options over ND messages November 2007 Author's Address Suresh Krishnan Ericsson 8400 Decarie Blvd. Town of Mount Royal, QC Canada Phone: +1 514 345 7900 x42871 Email: suresh.krishnan@ericsson.com Krishnan Expires May 14, 2008 [Page 14] Internet-Draft Carrying DHCP Options over ND messages November 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Krishnan Expires May 14, 2008 [Page 15]