Network Working Group F. Xia Internet-Draft B. Sarikaya Expires: April 25, 2010 S. Jiang Huawei Technologies October 22, 2009 Usage of Host Generating Interface Identifier in DHCPv6 draft-xia-dhc-host-gen-id-02.txt 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 April 25, 2010. Copyright Notice Copyright (c) 2009 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 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. Xia, et al. Expires April 25, 2010 [Page 1] Internet-Draft Host Generating Interface Identifier October 2009 Abstract This document describes a procedure for configuring a host's IPv6 address which prefix is allocated from a DHCPv6 server while it's interface identifier is independently generated by the host. The method is applicable to Cryptographically Generated Addresses (CGA). Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Address Auto-configuration in SEND . . . . . . . . . . . . . . 4 4. DHCPv6 Operation . . . . . . . . . . . . . . . . . . . . . . . 4 5. DHCPv6 Options . . . . . . . . . . . . . . . . . . . . . . . . 6 5.1. Identity Association for Prefix Assignment Option . . . . 6 5.2. IA_PD Prefix option . . . . . . . . . . . . . . . . . . . 8 5.3. IA Address Option . . . . . . . . . . . . . . . . . . . . 8 6. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 8 7. IANA consideration . . . . . . . . . . . . . . . . . . . . . . 8 8. Security Considerations . . . . . . . . . . . . . . . . . . . 8 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 10.1. Normative References . . . . . . . . . . . . . . . . . . . 9 10.2. Informative references . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Xia, et al. Expires April 25, 2010 [Page 2] Internet-Draft Host Generating Interface Identifier October 2009 1. Introduction [RFC3315] describes the operation of address assignment by a DHCP server. A client uses a Solicit message to discover DHCP servers configured to assign addresses. A server sends an Advertise message in response to announce the availability of the server to the client. The client then uses a Request message to request addresses. The server then returns addresses in a Reply message. The operation assumes that the server is responsible for the assignment of an integral address which include prefix and interface identifier parts as described in [RFC4291]. [RFC3633] defines Prefix Delegation options providing a mechanism for automated delegation of IPv6 prefixes using the DHCPv6. This mechanism is intended for delegating a long-lived prefix from a delegating router to a requesting router. The practice of separating prefix assignment from interface identifier assignment is only used for routers not hosts. [RFC3972] describes a method for binding a public signature key to an IPv6 address in the Secure Neighbor Discovery (SEND) protocol [RFC3971]. The basic idea is to generate the interface identifier (i.e., the rightmost 64 bits) of the IPv6 address by computing a cryptographic hash of the public key. That is, the host decides its interface identifier. As for the prefix part of the CGA, it is probably got through Router Advertisement message defined in [RFC4861], or through DHCPv6 operations defined in this document. [I-D.ietf-csi-dhcpv6-cga-ps]describes potential issues in the interaction between DHCPv6 and CGA. A usage of DHCPv6 for generating CGA is proposed in the document to facilitate separation of prefix and interface identifier assignment. A host's IPv6 address prefix is allocated from a DHCPv6 server while interface identifier is independently generated by the host. 2. Terminology 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]. The terminology in this document is based on the definitions in [RFC3315], in addition to the ones specified in this section Xia, et al. Expires April 25, 2010 [Page 3] Internet-Draft Host Generating Interface Identifier October 2009 derivative prefix: A prefix is derived from another prefix. For example, a /64 prefix is derived from a /48 prefix, that is, the /64 prefix has the same leftmost 48 bits with the /48 prefix. authorized prefix: A specific router is given a specific set of subnet prefixes to advertise; other routers have an authorization to advertise other subnet prefixes. In [RFC3971],Certification Path Advertisement message is used to convey authorized prefixes. 3. Address Auto-configuration in SEND Router Advertisements in [RFC4861] allow routers to inform hosts how to perform Address Auto-configuration. For example, routers can specify whether hosts should use DHCPv6 and/or stateless address configuration. In Router Advertisement message, M and O bits are used for indication of address auto-configuration mode. Whatever address auto-configuration mode a host uses, the following two parts are necessary for the host to formulate it's IPv6 address: o A prefix part. In [RFC3971], Certification Path Solicitation and Certification Path Advertisement messages are designed for verifying routers being authorized to act as routers. Certification Path Advertisement message can also be used to verify that routers are authorized to advertise a certain set of subnet prefixes. In stateless auto-configuration mode, the prefixes in Router Advertisement message should be a subset of authorized prefixes, or derivative prefixes from authorized prefixes. In the stateful auto-configuration mode, Section 4 illustrates a procedure for prefix allocation from a DHCPv6 server. o An interface identifier. The basic idea of [RFC3972] is to generate the interface identifier (i.e., the rightmost 64 bits) of the IPv6 address by computing a cryptographic hash of a public key of a host. The host is responsible for interface identifier generation. 4. DHCPv6 Operation Figure 1 shows the operation of separating prefix assignment and interface identifier generation. Xia, et al. Expires April 25, 2010 [Page 4] Internet-Draft Host Generating Interface Identifier October 2009 +------------+ +-----------+ |Host(Client)| |DHCP Server| +------------+ +-----------+ | | | | | | | 1 Solicit | |---------------------> | | | | 2 Advertise | |<--------------------- | | | | | 3 Combination of Prefix | and Interface Identifier | | | | | | 4 Request | |---------------------> | | | | 5 Reply | |<--------------------- | | | | | Figure 1: DHCPv6 Operation 1. A host uses a Solicit message to discover DHCP servers configured to assign prefixes for the host. Identity Association for Prefix Delegation Option (IA_PD) is defined in [RFC3633] for prefix delegation between a requesting router and delegating router. Referring to the definition, we design Identity Association for Prefix Assignment Option (IA-PA) in Section 5.1 for prefix assignment from a DHCPv6 server to a host. The host uses hints for prefix assignment preference. The hints are authorized prefixes advertised by an authorized router through Certification Path Advertisement defined in [RFC3971]. 2. Based on the hints, the DHCP server assigns one or more prefixes to the host. The assigned prefixes SHOULD be a subset of the authorized prefixes or derivative prefixes of the authorized prefixes. Identity Association for Prefix Assignment Option in Section 5.1 is used for conveying the assigned prefixes. If there is not a proper prefix available, a status-code is returned to the host and the procedure is terminated. 3. The host generates an interface identifier and formulates a combined IPv6 address by concatenating the assigned prefix and the self-generated interface identifier. There are many ways to Xia, et al. Expires April 25, 2010 [Page 5] Internet-Draft Host Generating Interface Identifier October 2009 generate interface identifier. [RFC3972] defines a method to generate the interface identifier by computing a cryptographic hash of a public key of the host. 4. The host sends a Request message for confirming usage of the combined address. An IA Address option described in Section 5.3 SHOULD be included to convey the combined address. 5. The DHCP server SHOULD verify the uniqueness of the combined IP address, and send Reply with IA Address option to grant the usage of the combined address. Otherwise, a status code is included to deny the usage of the combined address. 5. DHCPv6 Options In this section, one new option is defined, Identity Association for Prefix Assignment Option . At the same time, we extend the usage of existing options, IA_PD Prefix and IA Address option. 5.1. Identity Association for Prefix Assignment Option The IA_PA option is used to carry a prefix assignment identity association, the parameters associated with the IA_PA and the prefixes associated with it. The format of the IA_PA option is: Xia, et al. Expires April 25, 2010 [Page 6] Internet-Draft Host Generating Interface Identifier October 2009 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_IA_PA | option-length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IAID (4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | T1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | T2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . IA_PA-options . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code: OPTION_IA_PA (TDB by IANA) option-length: 12 + length of IA_PA-options field. IAID: The unique identifier for this IA_PA; the IAID must be unique among the identifiers for all of this host's IA_PAs. T1: The time at which the host should contact the DHCPv6 server from which the prefixes in the IA_PA were obtained to extend the lifetimes of the prefixes assigned to the IA_PA; T1 is a time duration relative to the current time expressed in units of seconds. T2: The time at which the host should contact any available DHCPv6 server to extend the lifetimes of the prefixes assigned to the IA_PA; T2 is a time duration relative to the current time expressed in units of seconds. IA_PA-options: Options associated with this IA_PA. The details of the fields are similar to the IA_PD option description in [RFC3633]. The difference is here a DHCP server and a host involved, while a delegating router and requesting router involved in [RFC3633]. Xia, et al. Expires April 25, 2010 [Page 7] Internet-Draft Host Generating Interface Identifier October 2009 5.2. IA_PD Prefix option IA_PD Prefix option in [RFC3633] is reused here. Originally the option is used for conveying prefix information between a delegating router and a requesting router. Here the IA_PD Prefix option is used to specify IPv6 address prefixes associated with an IA_PA in Section 5.1. The IA_PD Prefix option must be encapsulated in the IA_PA-options field of an IA_PA option. 5.3. IA Address Option The IA Address option in [RFC3315] is reused here. It must be encapsulated in the Options field of an IA_NA or IA_TA option. IA_NA and IA_TA are also described in [RFC3315]. A host sends a DHCPv6 message with an IA Address option to a DHCPv6 server for validating the usage of an address in the option. 6. Applicability In point-to-point link model, DHCPv6 operation with host generating interface identifier described in this document may be used. [RFC4968] provides different IPv6 link models that are suitable for 802.16 based networks and a point-to-point link model is recommended. Also, 3GPP and 3GPP2 have earlier adopted the point-to-point link model based on the recommendations in [RFC3314]. In this model, one prefix can only be assigned to one interface of a host (mobile station) and different hosts (mobile stations) can't share a prefix. The unique prefix can be used to identify the host. It is not necessary for a DHCP server to generate an interface identifier for the host. The host may generates it's interface identifier as described in [RFC4941]. An interface identifier could even be generated via random number generation. 7. IANA consideration The option code OPTION_IA_PA SHOULD be assigned by IANA. 8. Security Considerations Security considerations in DHCPv6 are described in [RFC3315]. To guard against attacks through prefix assignment and address confirmation, a host and a DHCPv6 server SHOULD use DHCP authentication as described in section "Authentication of DHCP Xia, et al. Expires April 25, 2010 [Page 8] Internet-Draft Host Generating Interface Identifier October 2009 messages" of [RFC3315]. 9. Acknowledgements 10. References 10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, September 2007. [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005. [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", RFC 3972, March 2005. [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. [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6", RFC 3633, December 2003. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006. [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy Extensions for Stateless Address Autoconfiguration in IPv6", RFC 4941, September 2007. 10.2. Informative references [RFC4968] Madanapalli, S., "Analysis of IPv6 Link Models for 802.16 Based Networks", RFC 4968, August 2007. [RFC3314] Wasserman, M., "Recommendations for IPv6 in Third Generation Partnership Project (3GPP) Standards", RFC 3314, September 2002. [I-D.ietf-csi-dhcpv6-cga-ps] Xia, et al. Expires April 25, 2010 [Page 9] Internet-Draft Host Generating Interface Identifier October 2009 Jiang, S., Shen, S., and T. Chown, "DHCPv6 and CGA Interaction: Problem Statement", draft-ietf-csi-dhcpv6-cga-ps-00 (work in progress), October 2009. Xia, et al. Expires April 25, 2010 [Page 10] Internet-Draft Host Generating Interface Identifier October 2009 Authors' Addresses Frank Xia Huawei Technologies 1700 Alma Dr. Suite 500 Plano, TX 75075 Phone: +1 972-509-5599 Email: xiayangsong@huawei.com Behcet Sarikaya Huawei Technologies 1700 Alma Dr. Suite 500 Plano, TX 75075 Phone: +1 972-509-5599 Email: sarikaya@ieee.org Sheng Jiang Huawei Technologies KuiKe Building, No.9 Xinxi Rd., Shang-Di Information Industry Base, Hai-Dian District, Beijing 100085 P.R. China Phone: +86 10-82836774 Email: shengjiang@huawei.com Xia, et al. Expires April 25, 2010 [Page 11]