Network Working Group F. Xia Internet-Draft B. Sarikaya Expires: August 18, 2008 Huawei USA February 15, 2008 Usage of Host Generating Interface Identifier in DHCPv6 draft-xia-dhc-host-gen-id-00.txt 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 August 18, 2008. Copyright Notice Copyright (C) The IETF Trust (2008). Xia & Sarikaya Expires August 18, 2008 [Page 1] Internet-Draft Host Generating Interface Identifier February 2008 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 . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Address Auto-configuration in SEND . . . . . . . . . . . . . . 4 4. DHCPv6 Operation . . . . . . . . . . . . . . . . . . . . . . . 5 5. DHCPv6 Options . . . . . . . . . . . . . . . . . . . . . . . . 6 5.1. Identity Association for Prefix Assignment Option . . . . 6 5.2. IA_PD Prefix option . . . . . . . . . . . . . . . . . . . 8 5.3. IA Address Validation Option . . . . . . . . . . . . . . . 8 6. IANA consideration . . . . . . . . . . . . . . . . . . . . . . 9 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 9.1. Normative References . . . . . . . . . . . . . . . . . . . 9 9.2. Informative references . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Intellectual Property and Copyright Statements . . . . . . . . . . 12 Xia & Sarikaya Expires August 18, 2008 [Page 2] Internet-Draft Host Generating Interface Identifier February 2008 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. The following are some scenarios in which separation of prefix and interface identifier assignment is necessary. o A DHCP server is incapable of generating an interface identifier for a host. [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 it's interface identifier. o A prefix is sufficient to identify a host. [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. A usage of DHCPv6 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. Xia & Sarikaya Expires August 18, 2008 [Page 3] Internet-Draft Host Generating Interface Identifier February 2008 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 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. Xia & Sarikaya Expires August 18, 2008 [Page 4] Internet-Draft Host Generating Interface Identifier February 2008 4. DHCPv6 Operation Figure 1 shows the operation of separating prefix assignment and interface identifier generation using DHCPv6. +------------+ +-----------+ |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. In CGA scenario, 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. In CGA scenario, the assigned prefixes SHOULD be a subset of the authorized prefixes or derivative prefixes of the authorized prefixes. Identity Association for Prefix Assignment Xia & Sarikaya Expires August 18, 2008 [Page 5] Internet-Draft Host Generating Interface Identifier February 2008 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 generate interface identifier. [RFC3972] defines a method to generate the interface identifier by computing a cryptographic hash of a public key of the host. [RFC4941] describes another way in which interface identifier is derived from IEEE 802 addresses. An interface identifier could even be generated via random number generation. 4. The host sends a Request message for confirming usage of the combined address. An IA Address Validation option defined 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 Validation option to grant the usage of the combined address. Otherwise, a status code is included in the replied IA Address Validation option to deny the usage of the combined address. 5. DHCPv6 Options In this section, two new options are defined, Identity Association for Prefix Assignment Option and IA Address Validation Option. At the same time, we extend the usage of an existing option, IA_PD Prefix 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 & Sarikaya Expires August 18, 2008 [Page 6] Internet-Draft Host Generating Interface Identifier February 2008 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 & Sarikaya Expires August 18, 2008 [Page 7] Internet-Draft Host Generating Interface Identifier February 2008 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 Validation Option The IA Address Validation option must be encapsulated in the Options field of an IA_NA or IA_TA option. IA_NA and IA_TA are described in [RFC3315]. A host sends this option to a DHCP server for validating the usage of an address in the option. 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_IAADDR_VAL | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | IPv6 address | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | preferred-lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | valid-lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . IAaddr-options . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code OPTION_IAADDR_VAL(TDB by IANA) option-len 24 + length of IAaddr-options field. IPv6 address An IPv6 address. preferred-lifetime The preferred lifetime for the IPv6 address in the option, expressed in units of seconds. valid-lifetime The valid lifetime for the IPv6 address in the option, expressed in units of seconds. Xia & Sarikaya Expires August 18, 2008 [Page 8] Internet-Draft Host Generating Interface Identifier February 2008 IAaddr-options Options associated with this address. The status of any operations involving this IA Address Validation is indicated in a Status Code option in the IAaddr-options field. The details of the fields are the same as the description in [RFC3315]. 6. IANA consideration The value of OPTION_IA_PA and OPTION_IAADDR_VAL should assigned by IANA. A status code needs to be assgined by IANA: ValdidationFailure: a DHCPv6 server can't grant the usage of an address in IA Address Validation Option 7. 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 messages" of [RFC3315]. 8. Acknowledgements 9. References 9.1. 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)", Xia & Sarikaya Expires August 18, 2008 [Page 9] Internet-Draft Host Generating Interface Identifier February 2008 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. 9.2. 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. Xia & Sarikaya Expires August 18, 2008 [Page 10] Internet-Draft Host Generating Interface Identifier February 2008 Authors' Addresses Frank Xia Huawei USA 1700 Alma Dr. Suite 500 Plano, TX 75075 Phone: +1 972-509-5599 Email: xiayangsong@huawei.com Behcet Sarikaya Huawei USA 1700 Alma Dr. Suite 500 Plano, TX 75075 Phone: +1 972-509-5599 Email: sarikaya@ieee.org Xia & Sarikaya Expires August 18, 2008 [Page 11] Internet-Draft Host Generating Interface Identifier February 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). 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). Xia & Sarikaya Expires August 18, 2008 [Page 12]