Internet Engineering Task Force T. Narten
Internet-Draft J. Johnson
Intended status: Standards Track IBM
Expires: January 9, 2011 July 8, 2010
Definition of the UUID-based DHCPv6 Unique Identifier (DUID-UUID)
draft-narten-dhc-duid-uuid-01
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
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This Internet-Draft will expire on January 9, 2011.
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. DUID-UUID Format . . . . . . . . . . . . . . . . . . . . . . . 4
3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6. Normative References . . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
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 so far:
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
The intention of DUIDs is that they 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.
In DHCPv4, all clients identify themselves to servers via the MAC
address of the interface on which the DHCP packet is sent. The MAC
address identifier generally remains constant across machine
restarts, installation of new operating system releases, changes in
hardware configuration such as addition or removal of storage
devices, etc. While the MAC address will change if the network
interface is replaced, this is a relatively uncommon event.
In contrast, the DUID-LLT and DUID-LL identifiers that a given device
may use are less likely to remain constant on some types of devices
and deployments. Specifically, when a machine goes through a multi-
step boot process, it may first load a simple boot loader, followed
by a one or more secondary loaders before the eventual actual target
system is loaded. In IPv4, all steps of a multi-step boot processes
that invoke DHCP are guaranteed to use the same MAC identifier during
each stage. In contrast, with DHCPv6, it is more difficult to ensure
or arrange that each boot stage uses the same identifier. First,
there are multiple DUID types, and different systems might choose to
use different formats. Second, 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, there is no guarantee 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.
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This document defines a new DUID type, based on the Universally
Unique IDentifier (UUID) [RFC4122]. UUIDs are already use in
practice and serve as an existing identifier that could be leveraged
by DHCP. For example, x86 based systems ship with an embedded UUID
in firmware that could be accessed for this purpose.
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 must use a DUID 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 DUID that is part of the system
firmware, or managed by the system firmware, would satisfy this
requirement.
It should be noted that use of a DUID-UUID will not by itself solve
all the problems motivating 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 is not a new problem.
2. DUID-UUID Format
The DUID-UUID is carried within Client Identifier or Server
Identifier options. It has the following format:
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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 (TBD) | UUID (128 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
| |
| -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
DUID-UUID format. .
Figure 1
DUID-Type - TBD (16 bits)
UUID - An RFC4122 UUID (128 bits)
3. 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.
4. IANA Considerations
IANA has assigned the value TBD for use by DHCPv6 DUID-UUID type
described in this document.
5. Security Considerations
This document does not create any new security considerations.
6. Normative References
[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.
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Authors' Addresses
Thomas Narten
IBM
Email: narten@us.ibm.com
Jarrod B. Johnson
IBM
Email: jarrod.b.johnson@gmail.com
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