IETF Mobile IPv6 Working Group Hee Jin Jang Internet-Draft Alper Yegin Expires: November 25, 2004 JinHyeock Choi SAMSUNG AIT May 31, 2004 DHCP Option for Home Agent Discovery in MIPv6 draft-jang-dhc-haopt-00.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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 November 25, 2004. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This draft defines a DHCP-based scheme to enable dynamic discovery of Mobile IPv6 home agent address and home subnet. A new DHCP option is defined to carry the information from a DHCP server to the DHCP client running on the mobile node. Jang, et al. Expires November 25, 2004 [Page 1] Internet-Draft DHCP Option for HA Discovery in MIPv6 May 2004 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. DHCP options for HA Dynamic Discovery . . . . . . . . . . . . 5 3.1 Home Agent Discovery Option . . . . . . . . . . . . . . . . . 5 3.2 Mobile Node Identifier Sub-option . . . . . . . . . . . . . . 5 3.3 Home Network Information Sub-option . . . . . . . . . . . . . 6 4. Option Usage . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.1 DHCP Server - Home Agent Relation . . . . . . . . . . . . . . 9 4.2 Mobile Node Considerations . . . . . . . . . . . . . . . . . . 9 4.3 DHCP Server Considerations . . . . . . . . . . . . . . . . . . 9 5. Security Considerations . . . . . . . . . . . . . . . . . . . 10 6. IANA Consideration . . . . . . . . . . . . . . . . . . . . . . 11 Normative References . . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 12 Intellectual Property and Copyright Statements . . . . . . . . 14 Jang, et al. Expires November 25, 2004 [Page 2] Internet-Draft DHCP Option for HA Discovery in MIPv6 May 2004 1. Introduction Before a mobile node can engage in Mobile IPv6 signaling with a home agent, it should either know the IP address of the home agent via preconfiguration, or dynamically discover it. Mobile IPv6 specification[2] describes how home agents can be dynamically discovered by mobile nodes that know the home subnet prefix. This scheme does not work when prefix information is not already available to the mobile node. This problem can be solved by delivering one or more home subnet prefix information to the mobile node by means of DHCP. Subsequently, the mobile node can engage dynamic home agent discovery using the prefix information. In addition to delivering the prefix information, DHCP can also be used to directly provide the IP addresses of the home agents that are available to the mobile node. The solution involves defining a new DHCP option to carry home agent IP address and home subnet prefix information. A similar solution has already been defined for Mobile IPv4 home agents[6]. As part of configuring the initial TCP/IP parameters, a mobile node can obtain home agent information for the subnet it is directly attached to, other subnets in the visited domain, or a subnet from its home domain. Mobile node can provide its identity in order to make the selection. For example the mobile node can provide its FQDN or its user's NAI and expect that a home agent information from its home domain is returned. The availability of the requested information depends on the DHCP server having prior knowledge or dynamically discovering it. While the specific details are outside the scope of this document, use of static tables and AAA-assisted discovery are possible options. The mobile node may or may not be connected to the "home" subnet when it attempts to learn Mobile IPv6 home network information. This allows operators to centrally deploy home agents while being able to bootstrap mobile nodes that are already roaming. This scenario occurs when HMIP[7]is used, where the mobile node is required to discover the MAP (a special home agent) that is located multiple hops away from the mobile node's attachment point. Jang, et al. Expires November 25, 2004 [Page 3] Internet-Draft DHCP Option for HA Discovery in MIPv6 May 2004 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[1]. Most of terms used in this draft are defined in Mobile IPv6[2] and RFC3315[5]. Jang, et al. Expires November 25, 2004 [Page 4] Internet-Draft DHCP Option for HA Discovery in MIPv6 May 2004 3. DHCP options for HA Dynamic Discovery This section introduces DHCP options used for dynamic home agent discovery in Mobile IPv6. 3.1 Home Agent Discovery Option This is a new DHCP option for the dynamic home agent discovery. It acts as a container for the following sub-options: Mobile Node Identifier (MNId) and Home Network Information (HNInf) sub-options. The mobile node MUST include MNId sub-option along with its Option Request option in its request. If the DHCP server identifies any matching home agent address or home subnet prefix, it MUST deliver them via HNInf sub-option(s). 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_HADISCOVER | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + . Sub-options . . . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code OPTION_HADISCOVER (TBD). option-len Total length of the sub-options. 3.2 Mobile Node Identifier Sub-option Mobile node uses this sub-option to identify itself to the DHCP server. DHCP server uses this identification to determine the matching home agent and home subnet information. This identification allows mobile node to request information for a home subnet within the visited domain, or from a specific domain. It is assumed that the DHCP server has some mechanism to know or retrieve the requested Mobile IPv6 information. The specifics of these mechanisms are Jang, et al. Expires November 25, 2004 [Page 5] Internet-Draft DHCP Option for HA Discovery in MIPv6 May 2004 outside the scope of this draft. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | subopt-type | subopt-len | id-type | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + . . . Mobile Node Identifier . + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ subopt-type MNId_SUBOPT (TBD) subopt-len Length of the Mobile Node Identifier field plus 1. id-type The type of Mobile Node Identifier. Possible values are: 0 Any mobile node from the local domain 1 NAI 2 FQDN 3 Opaque o Type 0 indicates that the mobile node wants to discover the home agents and home subnets within the local domain where it is currently attached to. The length of the identifier field MUST be set to 0. o Type 1 and Type 2 indicate that the mobile node wants to learn the home agents and home subnets that match its NAI [3] [4] or FQDN, respectively. The Mobile Node Identifier field MUST be set to the NAI or FQDN of the mobile node. o Type 3 means the mobile node identifier does not have any specific format. Use of this type is application-specific. 3.3 Home Network Information Sub-option Jang, et al. Expires November 25, 2004 [Page 6] Internet-Draft DHCP Option for HA Discovery in MIPv6 May 2004 This is a sub-option is used to carry one or more home subnet prefix(es) and home agent address(es) to a mobile node. The option can carry a mix of home addresses and home subnet prefixes at the same time. The server MUST provide all of the matching home agent address(es) and home subnet prefix(es) in a HNinf Sub-option. If the server has no information to provide, it MUST reply with the Home Agent Discovery option and set its option-len field to zero. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | subopt-type | subopt-len |A| reserved | prefix length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + home agent address or prefix + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ subopt-type HNInf_SUBOPT (TBD) subopt-len 18 home agent address flag (A) 1-bit home agent address flag. When set, it indicates that the following data field contains the complete IPv6 address of a home agent. When the flag is set to zero, it indicates that the following data field contains only a home subnet prefix that the mobile node may use for the dynamic home agent address discovery mechanism as described in Section 11.4.1 of Mobile IPv6[1]. reserved Jang, et al. Expires November 25, 2004 [Page 7] Internet-Draft DHCP Option for HA Discovery in MIPv6 May 2004 This field is currently unused and reserved for future use. It MUST be initialized to zero by the sender and MUST be ignored by the receiver. prefix length 8-bit unsigned integer. The number of leading bits of the following 128-bit value that are valid as a home subnet prefix. The value ranges from 0 to 128. Jang, et al. Expires November 25, 2004 [Page 8] Internet-Draft DHCP Option for HA Discovery in MIPv6 May 2004 4. Option Usage The requesting and sending of this option follows the rules for DHCP options in [5]. 4.1 DHCP Server - Home Agent Relation The DHCP server does not have to be co-located with a home agent, or even be on the home subnet of the mobile node. Its location with respect to home network does not matter as long as it possesses the requested information. 4.2 Mobile Node Considerations When a Mobile IPv6 Mobile Node finds itself with neither a home subnet prefix nor a home agent address, it may request the needed information with Option Request Option. For instance, a mobile node connecting to a network for the first time may acquire a DHCP address and solicit for Home Agent information at the same time. A mobile node MUST identify itself with Mobile Node Identifier Sub-option to facilitate a DHCP server to provide the matching information. For example, a DHCP server may have information about home agents from several domains (and subnets). It relies on the mobile node identifier for determining which ones it should provide in response to the client's request. When the mobile node gets more than one home agent address, it MUST have a selection mechanism to determine which one to use for establishing a Mobile IPv6 session. In case it retrieves only home subnet prefix(es), it needs to perform dynamic home agent discovery to learn the IP addresses of the home agents. 4.3 DHCP Server Considerations It is assumed that the DHCP server has access to home network information for its clients for this option to be useful. The DHCP server can rely on pre-configuration, or some dynamic discovery mechanisms for obtaining this information. In case it does not have any information, or it cannot locate matching information based on the mobile node identifier, it returns a Home Agent Discovery Option with 0-length data. Jang, et al. Expires November 25, 2004 [Page 9] Internet-Draft DHCP Option for HA Discovery in MIPv6 May 2004 5. Security Considerations Secure delivery of home agent and home link information from a DHCP server to the mobile node (DHCP client) relies on the overall DHCP security. The particular option defined in this draft does not have additional impact on the DHCP security. DHCP authentication mechanism MUST be used when the operator seeks authentication of the requestor and the information source (DHCP server). In that case, the Mobile Node Identifier MUST be compatible with the DHCP client identifier. For example, if the Mobile Node Identifier type is 0, the DHCP client identifier MUST belong to the local domain. Aside from the DHCP client to server interaction, an operator must also ensure secure delivery of mobile IP information to the DHCP server. This is outside the scope of DHCP and the newly defined option. Jang, et al. Expires November 25, 2004 [Page 10] Internet-Draft DHCP Option for HA Discovery in MIPv6 May 2004 6. IANA Consideration This document introduces one new DHCPv6 option, Home Agent Discovery option which has two sub-options, Mobile Node Identifier and Home Network Information. The type numbers for new DHCP option and sub-options are currently TBD. An appropriate request will be made to IANA if this Internet draft gets accepted as an RFC. Jang, et al. Expires November 25, 2004 [Page 11] Internet-Draft DHCP Option for HA Discovery in MIPv6 May 2004 Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Johnson, D., Perkins, C. and J. Arkko, "Mobility Support in IPv6", draft-ietf-mobileip-ipv6-24 (work in progress), July 2003. [3] Aboba, B. and M. Beadles, "The Network Access Identifier", RFC 2486, January 1999. [4] Calhoun, P. and C. Perkins, "Mobile IP Network Access Identifier Extension for IPv4", RFC 2794, March 2000. [5] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. [6] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997. [7] Soliman, H., Castelluccia, C., Malki, K. and L. Bellier, "Hierarchical Mobile IPv6 mobility management (HMIPv6)", draft-ietf-mipshop-hmipv6-01 (work in progress), February 2004. [8] Levkowetz, H., "DHCP Option for Mobile IP Mobility Agents", draft-ietf-dhc-mipadvert-opt-02 (work in progress), February 2004. Authors' Addresses Hee Jin Jang i-Networking Lab Samsung AIT P.O. Box 111 Suwon 440-600 Korea EMail: heejin.jang@samsung.com Alper E. Yegin i-Networking Lab Samsung AIT 75 West Plumeria Drive San Jose, CA 95134 USA EMail: alper.yegin@samsung.com Jang, et al. Expires November 25, 2004 [Page 12] Internet-Draft DHCP Option for HA Discovery in MIPv6 May 2004 JinHyeok Choi i-Networking Lab Samsung AIT P.O. Box 111 Suwon 440-600 Korea EMail: athene@sait.samsung.co.kr Jang, et al. Expires November 25, 2004 [Page 13] Internet-Draft DHCP Option for HA Discovery in MIPv6 May 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication 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 implementors or users of this specification can be obtained from the IETF Secretariat. 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Expires November 25, 2004 [Page 14] Internet-Draft DHCP Option for HA Discovery in MIPv6 May 2004 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgement Thank Youn-Hee Han, Jung-Hoon Cheon and Xiaoyu Liu who discussed together and gave the helpful advice on this draft. Jang, et al. Expires November 25, 2004 [Page 15]