Internet Engineering Task Force T. Narten Internet-Draft J. Johnson Intended status: Standards Track IBM Expires: June 19, 2011 December 16, 2010 Definition of the UUID-based DHCPv6 Unique Identifier (DUID-UUID) draft-ietf-dhc-duid-uuid-02 Abstract This document defines a new DHCPv6 Unique Identifier (DUID) type, called DUID-UUID. DUID-UUIDs are derived from the already standardized UUID format. DUID-UUID makes it possible for devices to use UUIDs to identify themselves to DHC servers and vice versa. UUIDs are globally unique and readily available on many systems, making them convenient identifiers to leverage within DHCP. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on June 19, 2011. Copyright Notice Copyright (c) 2010 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as Narten & Johnson Expires June 19, 2011 [Page 1]
Internet-Draft DUID-UUID December 2010 described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. UUID Considerations . . . . . . . . . . . . . . . . . . . . . . 4 4. DUID-UUID Format . . . . . . . . . . . . . . . . . . . . . . . 5 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 Narten & Johnson Expires June 19, 2011 [Page 2]
Internet-Draft DUID-UUID December 2010 1. Introduction DHCP Unique Identifiers (DUIDs) are used in DHCPv6 to identify clients and servers. This document defines a new DHCP Unique Identifier (DUID) type that embeds a Universally Unique IDentifier (UUID) [RFC4122]. UUIDs are already in wide spread use and serve as an existing identifier that could be leveraged by DHCPv6. For example, x86 based systems ship with an embedded UUID in firmware that is readily available to the software running on the device. Although DUIDs are new to DHCPv6, identifying clients in DHCP via a UUID is not. DHCPv4 [RFC2132] defines a Client Machine Identifier Option (option 97) that embeds a UUID (aka GUID) [RFC4578]. This document extends that capability to DHCPv6. 2. Background In DHCPv6, clients identify themselves to servers via DHCP Unique Identifiers (DUIDs) [RFC3315]. DUIDs are identifiers that DHCP servers treat as opaque objects with no internal structure. DUIDs are intended to be globally unique, with no two devices using the same DUID. Three DUIDs types have been defined previously: DUID-LLT - the Link-Layer address of one of the device's network interfaces, concatenated with a timestamp DUID-EN - an Enterprise Number plus additional information specific to the enterprise DUID-LL - the Link-Layer address of one of the device's network interfaces DUIDs are intended to remain constant over time, so that they can be used as permanent identifiers for a device. In the case of DUID- LLTs, they are intended to be generated once, and then stored in stable storage and reused from that point forward. One issue that has arisen concerns devices that employ multi-step network boot loading. An initial step (typically run out of firmware) loads a small image that in turn loads a second image, and so forth, until the actual target system is loaded. Each step in the booting process may invoke DHCP. In some operational environments, it is important that each step in the sequence use the same DUID, so that the server knows it is getting requests from the same device and can return the proper configuration information (including the pointer to the correct image to load). Narten & Johnson Expires June 19, 2011 [Page 3]
Internet-Draft DUID-UUID December 2010 Unfortunately, none of the previously defined DUIDs are ideal for multi-step network booting. The DUID-LLT and DUID-LL identifiers that a given device may use are not guaranteed to remain constant across each booting step. Even if the different stages used DUID-LL or DUID-LLT, on devices with multiple interfaces, there is no way to guarantee that the same interface (and hence DUID) will be selected. Finally, in the case of DUID-LLT, even if the same interface were chosen, it can be difficult to ensure that each stage would use the same timestamp value. While a DUID-EN could be defined and used, such usage would be proprietary by definition. This document defines a new DUID type, based on the Universally Unique IDentifier (UUID) [RFC4122]. UUIDs are already used in practice and serve as an existing identifier that could be leveraged by DHCP. In some environments, a UUID-based DUID would be preferable to the other existing DUID types. It should be noted that use of a DUID-UUID will not by itself solve all the network boot problems described in this document. Given the availablility of a suitable DUID-UUID, implementations will still need to take steps to ensure that all boot stages use the same DUID- UUID as appropriate. Given that DHCP has already defined multiple DUID types, the question of which of several DUIDs to select from already exists -- and defining a new DUID type doesn't by itself help. It is believed, however, that network boot services can be configured to use a DUID-UUID and that other software can do so as well. Ensuring this happens in general is beyond the scope of this document. 3. UUID Considerations Although many UUIDs are in use today, not all UUIDs meet the requirements of the DHCP protocol (see Section 9 of [RFC3315]). DHCP UUIDs should be persistant across system restarts, across system reconfiguration events, system software and operating system upgrades or reinstallation, and be easily available to any part of the boot process that requires access to the DHCP UUID. For example, UUIDs used in Microsoft's Component Object Module (COM), and for labeling partitions in filesystems, are likely not appropriate as they may not be accessible to firmware boot loaders, and can change over time. Implementations of this specification using DUID-UUID must select a UUID that is persistent across system restart and reconfiguration events, and that is available to all DHCP protocol agents that may need to identify themselves. For instance, a UUID that is part of the system firmware, or managed by the system firmware, would satisfy this requirement. Narten & Johnson Expires June 19, 2011 [Page 4]
Internet-Draft DUID-UUID December 2010 4. DUID-UUID Format The DUID-UUID is carried within Client Identifier or Server Identifier options. It has the following format: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | DUID-Type (4) | UUID (128 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | | | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- DUID-UUID format. . Figure 1 DUID-Type - DUID-UUID (4) - (16 bits) UUID - An RFC4122 UUID (128 bits) 5. Acknowledgements This document was inspired by a discussion on the DHC mailing list in November, 2009 on the topic of netboot for IPv6. Specifically, some scenarios were described where it was difficult to do something in DHCPv6 that had worked well in DHCPv4. We would like to thank the following individuals in particular for their specific comments and suggestions on this draft: Andre Kostur, Suresh Krishnan, Ted Lemon, Bernie Volz & Vincent Zimmer. 6. IANA Considerations IANA has assigned the value 4 for use by the DHCPv6 DUID-UUID type. [TO BE REMOVED UPON PUBLICATION: IANA should update the registry entry for the DUID-UUID DUID-Type and mark the assignment permanent.] 7. Security Considerations DHCP traffic between a client and server is sent in the clear. An eavesdroppper residing on the path between the client and server Narten & Johnson Expires June 19, 2011 [Page 5]
Internet-Draft DUID-UUID December 2010 could see DHCP traffic and obtain the UUID for a particular machine. This may raise some privacy issues. 8. References 8.1. Normative References [RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor Extensions", RFC 2132, 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. [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally Unique IDentifier (UUID) URN Namespace", RFC 4122, July 2005. 8.2. Informative References [RFC4578] Johnston, M. and S. Venaas, "Dynamic Host Configuration Protocol (DHCP) Options for the Intel Preboot eXecution Environment (PXE)", RFC 4578, November 2006. Authors' Addresses Thomas Narten IBM Email: narten@us.ibm.com Jarrod B. Johnson IBM Email: jarrod.b.johnson@gmail.com Narten & Johnson Expires June 19, 2011 [Page 6]
