Network Working Group C. Cadar Internet-Draft NEC (Netlab) Expires: August 9, 2004 C. Strauf JOIN (WWU) February 9, 2004 DHCPv6 IPv4 Information Options draft-cadar-dhc-dhcpv6-v4options-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 August 9, 2004. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract To ease the management of a site, the Dynamic Host Configuration Protocol (DHCP) is often used. DHCP exists both for the Internet Protocol Version 4 (DHCPv4 for IPv4) and Version 6 (DHCPv6 for IPv6). To avoid possible pitfalls that occur if both DHCP versions are used and to avoid redundancy, IPv4 Information Options may be transmitted using DHCPv6 as described in this document. In dual-stack IPv4/IPv6 scenarios that employ DHCPv6, DHCPv4 can be completely replaced by using the DHCPv6 IPv4 Information Options. Cadar & Strauf Expires August 9, 2004 [Page 1] Internet-Draft DHCPv6 IPv4 Information Options February 2004 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements notation & Naming Conventions . . . . . . . . . . 4 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Simultaneous DHCPv6 & DHCPv4: Issues . . . . . . . . . . . . . 7 5. Prerequisites & Scenarios . . . . . . . . . . . . . . . . . . 8 6. Integrating DHCPv4 options into DHCPv6 . . . . . . . . . . . . 9 7. State Machine/Protocol Machinery . . . . . . . . . . . . . . . 10 8. IPv4 Information Option Message Format . . . . . . . . . . . . 11 8.1 IPv4 Address Option . . . . . . . . . . . . . . . . . . . . . 11 8.2 The Broadcast Address Option . . . . . . . . . . . . . . . . . 11 8.3 IPv4 Netmask Option . . . . . . . . . . . . . . . . . . . . . 12 8.4 IPv4 Router Option . . . . . . . . . . . . . . . . . . . . . . 12 8.5 The Host Name Option . . . . . . . . . . . . . . . . . . . . . 13 8.6 World Wide Web Server Option . . . . . . . . . . . . . . . . . 14 8.7 IPv4 DNS Servers & Search Domains . . . . . . . . . . . . . . 14 8.8 IPv4 Forwarding Enable/Disable Option . . . . . . . . . . . . 14 9. Security Considerations . . . . . . . . . . . . . . . . . . . 16 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18 References . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 19 Intellectual Property and Copyright Statements . . . . . . . . 20 Cadar & Strauf Expires August 9, 2004 [Page 2] Internet-Draft DHCPv6 IPv4 Information Options February 2004 1. Introduction The Dynamic Host Configuration Protocol (DHCP) is used in both domains of IPv4 and IPv6 to configure hosts automatically. Currently DHCP for IPv4 (DHCPv4) [RFC2131] and DHCP for IPv6 (DHCPv6) [RFC3315] are defined and deployed. One phase during the transition from IPv4 to IPv6 can be the deployment of IPv4 and IPv6 at the same time ("dual-stack"). In particular, a host in a specific broadcast domain has both IPv4 and IPv6 connectivity on the same port and has both an IPv4 and IPv6 stack provided by its operating system. Networks running IPv4 or IPv6 protocol use either DHCPv4 or DHCPv6, but running both version of DHCP in parallel may cause problems that are going to be identified in this document. Hosts being configured using both mechanisms at the same time may end up with a non-useful configuration. This document discusses the integration of DHCPv4 functionality into DHCPv6, and so enabling the configuration of both address domains with a single dynamic host configuration protocol. This is achieved by adapting DHCPv4 options to DHCPv6 option format and by using existing DHCPv6 transport mechanisms. Cadar & Strauf Expires August 9, 2004 [Page 3] Internet-Draft DHCPv6 IPv4 Information Options February 2004 2. Requirements notation & Naming Conventions 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 following conventions and abbreviations will be used within this document: o "DHCPv4" denotes the Dynamic Host Configuration Protocol according to [RFC2131]. o "DHCPv6" denotes the Dynamic Host Configuration Protocol according to [RFC3315]. o "Dual-stack" networks provide both IPv4 and IPv6 connectivity to hosts. o "Dual-stack" hosts have both IPv4 and IPv6 stacks in their operating system and both stacks are enabled. Cadar & Strauf Expires August 9, 2004 [Page 4] Internet-Draft DHCPv6 IPv4 Information Options February 2004 3. Overview The Dynamic Host Configuration Protocol is a common management tool to automatically configure clients in a particular site without the need of the administrator's interaction. This configuration includes but is not limited to IP addresses, default routers (IPv4) and netmasks (IPv4). DHCPv4 or DHCPv6 are the transport and exchange protocols for this information. DHCP is not only used for large sites. It is also commonly used in SOHO sites e.g. on small broadband access routers to automatically configure clients that are attached to the local network. There are two, in some scenarios three different components in DHCP exchanges: there are always a client and a server involved. In some sites, there also exist relay agents that relay DHCP messages between different broadcast domains. However, relay agents do not alter the information conveyed with the DHCP protocols and hence do not need special attention in this document. As stated before, there are two different DHCP standards: DHCPv4 and DHCPv6. Both exist independently, and DHCPv6 is not backward compatible with regards to the protocol. The message and option sizes differ and the client identification is handled in a different way (DHCPv4 uses MAC addresses to identify a client, DHCPv6 uses DHCP Unique Identifiers (DUIDs) and Identity Association Identifiers (IAIDs)). In theory, both DHCP versions could exist in parallel in the same site and a host may be both a DHCPv4 and DHCPv6 client. But there are certain pitfalls described in Section 4, which complicate this co-existence. Therefore it is convenient in a number of scenarios that are identified in Section 5 to use either DHCPv4 or DHCPv6 but not both on the same host. This is only possible if DHCPv6 is capable of transporting information that is normally transported using DHCPv4. The purpose of this document is to present a practical solution to this problem by defining DHCPv6 options that contain IPv4 information. Choosing DHCPv6 over DHCPv4 instead of DHCPv4 over DHCPv6 is done for the following reasons: o DHCPv6 is more sophisticated in a number of ways (authentication, identification of clients, etc.) o DHCPv6 options can easily be adapted to hold IPv4 information o New DHCPv6 options are easily created to convey IPv4 information o The client's identity is independent of the client's hardware. A change of the MAC address of a client has no impact on the client's identity stored on the server It is important to note that this document does not introduce backward compatibility to DHCPv4 in DHCPv6 on the protocol level. The Cadar & Strauf Expires August 9, 2004 [Page 5] Internet-Draft DHCPv6 IPv4 Information Options February 2004 state machinery and option format of DHCPv6 stays untouched and fully compliant with [RFC3315]. Furthermore, it is not the intention of this document to render DHCPv4 obsolete e.g. in IPv4-only sites. Cadar & Strauf Expires August 9, 2004 [Page 6] Internet-Draft DHCPv6 IPv4 Information Options February 2004 4. Simultaneous DHCPv6 & DHCPv4: Issues Issues that occur when employing DHCPv4 and DHCPv6 simultaneously are identified in the document: "IPv4 and IPv6 Dual-Stack Issues for DHCPv6", T. Chown, S. Venaas, C. Strauf, February 2004, draft-chown-dhc-dual-stack-00 (work in progress). Cadar & Strauf Expires August 9, 2004 [Page 7] Internet-Draft DHCPv6 IPv4 Information Options February 2004 5. Prerequisites & Scenarios To use DHCPv6 IPv4 Information Options, the following prerequisites must be met: o A DHCPv6 client MUST have both IPv4 and IPv6 stacks in their operating systems. IPv4 Information Options MUST NOT be used if an IPv4 stack is not present. o A DHCPv6 client that requests IPv4 Information Options SHOULD NOT additionally use DHCPv4. o Neither DHCPv6-clients nor -servers that use IPv4 Information Options need to ensure the existence of IPv4 connectivity. The usage of IPv4 Information Options is the preferred method of providing IPv4 information to clients in a dual-stack network where DHCPv6 is deployed. In such dual-stack networks, the following differentiation is made: 1. IPv4-only clients that use DHCPv4. 2. Dual-stack or IPv6-only clients that use DHCPv6. Dual-stack clients that use DHCPv6 SHOULD NOT additionally use DHCPv4. Instead, IPv4 Information Options SHOULD be requested using DHCPv6. Information like IPv4 address, IPv4 netmask and IPv4 default router is then transmitted using DHCPv6 transport. DHCPv6 can even be used if no global IPv6 connectivity is present but site scoped IPv6 multicast addresses can be used by clients to contact DHCPv6 servers. Contrary to DHCPv4, MAC addresses are not used to identify a client. Instead, the DHCP Unique Identifier (DUID) and Identity Association Identifier (IAID) as defined in [RFC3315] are used in the usual manner for all DHCPv6 exchanges. This reduces the overhead of managing MAC addresses additionally to DUID and IAID. Cadar & Strauf Expires August 9, 2004 [Page 8] Internet-Draft DHCPv6 IPv4 Information Options February 2004 6. Integrating DHCPv4 options into DHCPv6 There are two ways of integrating IPv4 specific options into DHCPv6. Existing DHCPv4 options can be converted to match the DHCPv6 option format or existing DHCPv6 options can be modified to transport IPv4 information. The latter method is preferred if DHCPv6 offers more convenient management methods or if it facilitates the option's implementation. In every case, a new option code needs to be assigned by the IANA. For DHCPv6 options, the address field that normally carries IPv6 addresses can be reduced from a 128 bits to a 32 bits length. Other IPv6 specific parts also need to be adjusted. DHCPv4 options need to be reworked to fit the DHCPv6 option format. The modified DHCPv4 options can be put into a different context in some cases, e.g. as a sub-option of another option. The necessity for this has to be decided for each case. Cadar & Strauf Expires August 9, 2004 [Page 9] Internet-Draft DHCPv6 IPv4 Information Options February 2004 7. State Machine/Protocol Machinery The impact of introducing IPv4 options in the DHCPv6 protocol stack is minimal. The OPTION_IAADDR_IPv4 option MAY be encapsulated in a IA_NA or IA_TA option and its behavior is the same as for IA Address Option described in [RFC3315]. As for the other options they MAY be requested by the clients using the Option Request option described in Section 22.7 of [RFC3315]. The IPv6 address lifetime extension procedure described in [RFC3315] applies to IPv4 addresses as well, the other IPv4 related options, such as DNS and Default Routers, MUST be included in the RENEW/REBIND messages, the IAADDR_IPv4 option containing the IPv4 address for renewal MAY coexist together with an IPv6 IAADDR option in the same IA_TA or IA_NA option of the DHCPv6 message. On reception of an IA option which contains both OPTION_IAADDR option and an OPTION_IAADDR_IPv4 option, the client SHOULD process both options by attaching the IPv6 address to the IPv6 stack of the interface it was intended to and the IPv4 address to its IPv4 stack of the same interface. Also, if the client requested the DNS option the server SHOULD send a DNS server address list containing the DNS servers in order of preference; the list MAY contain both IPv6 addresses and IPv4 addresses in the form of IPv6 compatibility addresses. The server MAY change the IPv4/IPv6 addresses and/or DNS settings of the client at any moment with the RECONFIGURE message. Message relaying SHOULD use IPv6 addresses only as described in [RFC3315]. Cadar & Strauf Expires August 9, 2004 [Page 10] Internet-Draft DHCPv6 IPv4 Information Options February 2004 8. IPv4 Information Option Message Format 8.1 IPv4 Address Option The IAADDR_IPv4 option must be embedded in an IA_NA or IA_TA field as defined in [RFC3315], sections 22.4 and 22.5. The OPTION_IAADDR_IPv4 is depicted in Figure 1. 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_IPv4 | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | preferred-lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | valid-lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . IAaddr-options . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: OPTION_IAADDR_IPv4 option-code: OPTION_IAADDR_IPv4. option-len: 24 + length of IAaddr-options field. IPv4 address: An IPv4 address. preferred-lifetime: The preferred lifetime for the IPv4 address in the option, expressed in units of seconds. valid-lifetime: The valid lifetime for the IPv4 address in the option, expressed in units of seconds. IAaddr-options: Options associated with this address. 8.2 The Broadcast Address Option The IAaddr-options address field of OPTION_IAADDR_IPv4 MAY contain a broadcast options related to the specified IPv4 address. This option specifies the broadcast address in use on the client's subnet Cadar & Strauf Expires August 9, 2004 [Page 11] Internet-Draft DHCPv6 IPv4 Information Options February 2004 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_BROADCAST | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | broadcast-address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: OPTION_BROADCAST option-code: OPTION_BROADCAST. option-len: 4 octets. broadcast-address: The specification of the broadcast address given by the server. 8.3 IPv4 Netmask Option The IAaddr-options address field of OPTION_IAADDR_IPv4 may contain a netmask options related to the specified IPv4 address: 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_NETMASK | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Netmask-address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: OPTION_NETMASK option-code: OPTION_NETMASK. option-len: 4. Netmask-address: The netmask for the IPv4 address. 8.4 IPv4 Router Option The router option specifies a list of IP addresses for routers on the client's subnet. Routers SHOULD be listed in order of preference. Cadar & Strauf Expires August 9, 2004 [Page 12] Internet-Draft DHCPv6 IPv4 Information Options February 2004 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_ROUTER | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Router-address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Router-address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ................ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: OPTION_ROUTER option-code: OPTION_ROUTER. option-len: 4*(number of router addresses). Router-address: Address of the router for the IAID. 8.5 The Host Name Option This option specifies the name of the client. The name may or may not be qualified with the local domain name. See [RFC1035] for character set restrictions. The format of the Host Name option is: 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_HOST_NAME | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | hostname | | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: OPTION_HOST_NAME option-code: OPTION_HOST_NAME. option-len: Length of the "hostname" field in octets. hostname: The specification of the host name given by the server. Cadar & Strauf Expires August 9, 2004 [Page 13] Internet-Draft DHCPv6 IPv4 Information Options February 2004 8.6 World Wide Web Server Option The WWW server option specifies a list of WWW available to the client. Servers SHOULD be listed in order of preference. 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_WWW | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | server-address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | server-address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ................ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6: OPTION_WWW option-code: OPTION_WWW. option-len: 4*(number of server addresses). server-address: The server address. 8.7 IPv4 DNS Servers & Search Domains The DNS Configuration options described in [RFC3646] may be used to carry IPv4 addresses in the form of IPv6 compatibility addresses in OPTION_DNS_SERVERS. The DHCPv6 client should convert IPv6 compatibility addresses back to IPv4 addresses on reception before using them for configuration purposes. This is mandatory on host operating systems that cannot handle IPv6 compatibility addresses. All search domains that are necessary for normal operation can be transmitted using OPTION_DOMAIN_LIST in [RFC3646]. No additional client modifications or interactions are necessary. 8.8 IPv4 Forwarding Enable/Disable Option This option specifies whether the client should configure its IPv4 layer for packet forwarding. A value of 0 means disable IP forwarding, and a value of 1 means enable IP forwarding. Cadar & Strauf Expires August 9, 2004 [Page 14] Internet-Draft DHCPv6 IPv4 Information Options February 2004 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_FORWARDING | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | value | +-+-+-+-+-+-+-+-+ Figure 7: OPTION_FORWARDING option-code: OPTION_FORWARDING. option-len: 1 octet. value Value of Forwarding Enable/Disable Option. Cadar & Strauf Expires August 9, 2004 [Page 15] Internet-Draft DHCPv6 IPv4 Information Options February 2004 9. Security Considerations There are no additional or other security considerations than already mentioned in [RFC3315] and [RFC3646]. Cadar & Strauf Expires August 9, 2004 [Page 16] Internet-Draft DHCPv6 IPv4 Information Options February 2004 10. IANA Considerations The Internet Assigned Numbers Authority (IANA) needs to assign numbers to the following option codes from the DHCP option code space defined in section "IANA Considerations" of [RFC3315]: o OPTION_IAADDR_IPv4 o OPTION_NETMASK o OPTION_ROUTER o OPTION_HOST_NAME o OPTION_FORWARDING o OPTION_BROADCAST o OPTION_WWW Cadar & Strauf Expires August 9, 2004 [Page 17] Internet-Draft DHCPv6 IPv4 Information Options February 2004 11. Acknowledgments The authors would like to thank the following individuals for their input and comments (no particular order): Martin Stiemerling (NEC), Juergen Quittek (NEC), Christian Schild (JOIN), Tina Strauf (JOIN), Andre Stolze (JOIN), Ralph Droms (Cisco), Gunther Van de Velde (Cisco), Tim Chown (University of Southampton), Stig Venaas (UNINETT). Cadar & Strauf Expires August 9, 2004 [Page 18] Internet-Draft DHCPv6 IPv4 Information Options February 2004 References [RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987. [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. [RFC3646] Droms, R., "DNS Configuration options for Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646, December 2003. Authors' Addresses Cristian Cadar Netlab, NEC Europe Ltd. Kurfuersten-Anlage 36 Heidelberg D-69115 DE EMail: cristian.cadar@netlab.nec.de URI: http://www.netlab.nec.de Christian Strauf JOIN (University of Muenster) Roentgenstr. 9-13 Muenster D-48149 DE EMail: strauf@uni-muenster.de URI: http://www.join.uni-muenster.de Cadar & Strauf Expires August 9, 2004 [Page 19] Internet-Draft DHCPv6 IPv4 Information Options February 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. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. Full Copyright Statement Copyright (C) The Internet Society (2004). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assignees. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION Cadar & Strauf Expires August 9, 2004 [Page 20] Internet-Draft DHCPv6 IPv4 Information Options February 2004 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Cadar & Strauf Expires August 9, 2004 [Page 21]