INTERNET DRAFT Mike Henry
Intel Corp.
Feb 22, 1999
DHCP Options For Host System Characteristics
<draft-dittert-host-sys-char-03.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.
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Abstract
The interoperability of configuration services based on the Dynamic Host
Configuration Protocol (DHCP) [1] in an environment of heterogeneous
clients depends on clients accurately identifying themselves and their
relevant characteristics to configuration servers. The class identifier
provided through DHCP option 60 [2] helps in this regard, but such
identifiers essentially only enable clients and servers that are "good
friends" to find each other. This draft proposes the definition of three
options that convey particular, generally useful information about the
client system. This enables all servers to recognize this information,
and is a step toward a richer form of interoperability for configuration
services.
The options in question are
Option 93 - Client System Architecture
Option 94 - Client Network Device Interface
Option 97 - UUID/GUID-based Client Identifier
Subsequent to IANA issuing the above DHCP option numbers, the DHCP Working
Group has determined that use of these options is not appropriate. As a
result, it was agreed in the August 1998 IETF DHCP WG meeting that use of
Options 93, 94, and 97 as described in this draft would be allowed until
August of 2004 (six years), after which time the option numbers would be
made available for new options.
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In the interim, it is expected that systems using Options 93, 94, and 97
will be redefined to use Options 60 and 61. It is allowable that systems
may use both methods during the 6 year interim period as a means of
migrating to exclusive use of Options 60 and 61 for this functionality by
the end of the interim period.
The DHCP Working Group has agreed that this draft will be published as
an Informational RFC to document the expected term of use for Options 93,
94, and 97 as defined in this ID.
1.0 Introduction
The use of DHCP to provide clients with configuration information in
general, and boot images in particular can be complicated by several
circumstances. Among these are
1) clients in the same service domain with different system
architectures or hardware configurations
2) clients in the same service domain for which different software
configurations are desired
3) the desire to have clients and servers provided by different
vendors successfully interact
(By "clients in the same service domain" we mean clients, requests
from which can reach the same server.) A key element in enabling the
successful use of DHCP in such circumstances is the provision of
mechanisms by which clients can accurately identify themselves and
their relevant characteristics to a server.
For identifying characteristics of the client that are relevant to
the selection of a boot image, the currently available mechanisms are
the DHCP class identifier option (code 60) and the DHCP vendor
specific information option (code 43). By definition, the vendor
specific information option does not address the problem of enabling
interoperability of clients and servers provided by different
vendors. Information conveyed by the class identifier option could
enable interoperability, provided that a sufficiently specific and
complete set of class identifiers were defined and agreed to.
We suggest using an alternate approach, in which new, specific
options are used to convey the characteristics of the client that
determine which boot image(s) could run on the client, and the class
identifier is used as a (site-specific) designation of the desired
software configuration for the client. Section 2 defines two new
options that are useful for conveying the client's hardware
configuration.
For identifying the client as a unique entity, the currently
available mechanism is the DHCP client identifier option (code 61)
[2]. Section 3 of this draft defines an alternative option (code 97)
identifier type based on generated GUIDs - identifiers that are
guaranteed to be, or are very, very likely to be unique across time
and all clients.
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2.0 Client Characteristics Options
The options defined in this section provide the server with explicit
knowledge about the client system that is generally useful in
selecting an executable that the client can use as a boot image.
2.1 Client System Architecture Option
DHCP clients SHOULD include this option in DHCPDISCOVER and
DHCPREQUEST messages. Doing so provides the server with explicit
knowledge of the client's system architecture.
DHCP servers that use this option MAY include the option in
responses that contain a bootfile name. If included, the value of
the option MUST denote a system architecture for which the bootfile
named is valid. DHCP servers MUST NOT include this option in
responses that do not contain a bootfile name.
The format for this option is as follows:
Code Len System Arch Code
+-----+-----+-----+-----+
| 93 | 2 | s1 | s2 |
+-----+-----+-----+-----+
The currently defined types and their codes are
System Architecture Code
------------------- ----
Intel Architecture PC 0
NEC PC-9800 1
Intel Architecture 64 PC 2
DEC Alpha 3
ARCx86 4
Intel Lean Client 5
2.2 Client Network Device Interface Option
DHCP clients SHOULD include this option in DHCPDISCOVER and
DHCPREQUEST messages. Doing so provides the server with explicit
knowledge of the client's network device.
DHCP servers that use this option MAY include the option in
responses that contain a bootfile name. If included, the value of
the option MUST denote a network device for which the bootfile named
is valid. DHCP servers MUST NOT include this option in responses
that do not contain a bootfile name.
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Three types of network device specifications are defined for use with
this option:
* devices that support the Universal Network Driver Interface
(UNDI), as described in "Network PC System Design Guidelines: A
Reference for Designing Net PC Systems for Use with the
Microsoft Windows and Windows NT Operating Systems" [3]
* Plug-and-Play devices [5]
* PCI devices [6]
Each device that supports (UNDI) MUST be specified as an UNDI
device, regardless of whether it is also a Plug-and-Play device or a
PCI device. To specify an UNDI device, the option contains a type
code of 1 and the major and minor UNDI version numbers:
Code Len Type Major Minor
+-----+-----+-----+-----+-----+
| 94 | 3 | 1 | m1 | m2 |
+-----+-----+-----+-----+-----+
To specify a PCI network device, a type code of 2 is used, and the
vendor ID, device ID, class code, and revision are included:
Code Len Type Vendor ID Device ID Class code Rev
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| 94 | 9 | 2 | v1 | v2 | d3 | d4 | c1 | c2 | c3 | r1 |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
To specify a Plug-and-Play network device, a type code of 3 is used,
and the EISA device ID and the class code are included:
Code Len Type EISA device ID Class code
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| 94 | 8 | 3 | e1 | e2 | e3 | e4 | c1 | c2 | c3 |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
3.0 Unique Client Identifier
This option (code 97) provides a unique client identifier. Type 0 of
this identifier is defined to be in UUID/GUID format. A client
identifier option containing a type code of 0 MUST contain a 128-bit
UUID as follows:
Code Len Type Client UUID
+------+------+-----+------+------+------+
| 97 | 17 | 0 | g1 | g2 | ... |
+------+------+-----+------+------+------+
The format and content of the UUID MUST be as specified in the RPC
Specification from the Open Group [4].
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A client machine providing this option MUST use the same UUID value
each time the option is used. That is, the UUID MUST be static.
DHCP clients SHOULD include this option in all DHCP messages. Doing so
provides the server with a unique and static identifier for the client
platform.
4.0 References
[1] Droms, R. "Dynamic Host Configuration Protocol", RFC 2131
[2] Alexander,S. and Droms, R., "DHCP Options and BOOTP Vendor
Extension" RFC 2132.
[3] "Network PC System Design Guidelines: A Reference for
Designing Net PC Systems for Use with the Microsoft Windows
and Windows NT Operating Systems",
http://www.intel.com/managedpc
[4] CAE Specification
DCE 1.1: Remote Procedure Call
Document Number: C706
Universal Unique Identifier Appendix
Copyright (c) 1997 The Open Group
http://www.opengroup.org/onlinepubs/9629399/toc.htm
[5] Intel Corp. and Microsoft Corp., "Plug and Play ISA
Specification", Version 1.0a, May 5, 1994
[6] Peripheral Component Interconnect Special Interest Group,
"Peripheral Component Interconnect Specification", Revision
2.1, available through PCISIG,
http://www.pcisig.com/specs.html
5.0 Author's Address
Mike Henry
Intel Corporation, MS JF3-206
5200 NE Elam Young Pkwy
Hillsboro, OR 97124
Phone: (503) 264-9689
Email: mike.henry@intel.com
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