Dynamic Host Configuration Working M. Johnston
Group Intel Corporation
Internet-Draft January 21, 2005
Expires: July 22, 2005
DHCP Preboot eXecution Environment (PXE) Options
draft-ietf-dhc-pxe-options-01.txt
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
Define DHCP options being used by PXE and EFI clients.
Requirements Language
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 RFC 2119 [RFC2119].
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Revision history . . . . . . . . . . . . . . . . . . . . . . . 3
3. Option Definitions . . . . . . . . . . . . . . . . . . . . . . 3
3.1 Client System Architecture Type Option Definition . . . . 3
3.2 Client Network Interface Identifier Option Definition . . 4
3.3 Client Machine Identifier Option Definition . . . . . . . 5
3.4 Site Specific Options Being Requested By PXE Client . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. Normative References . . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . . 7
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1. Introduction
These DHCP options [RFC2131] are being widely used by PXE compliant
clients to uniquely identify booting client machines themselves and
their pre-OS runtime environment so the DHCP and/or PXE boot server
can return the correct OS bootstrap image (or pre-boot application)
name and server to the client. In the past, this work was done by
examining the network MAC address in the "chaddr" field in the BOOTP/
DHCP header and keeping a database of MAC addresses on the BOOTP/DHCP
server. This was deemed insufficient for large and complex networks
for two main reasons. 1) Multiple laptops could end up with the same
MAC address if the NIC was in a shared docking station. 2) Multiple
network devices and MAC addresses could be used by one machine for
redundancy or because of repairs. Another issue that came up was the
machine that could change its pre-OS runtime environment. This issue
caused the creation of another new option to identify the runtime
environment so the correct binary image could be matched up with the
booting machine. These options are defined in the PXE [pxe] and EFI
[efi] specifications and are being documented in this draft for
completeness within the IETF. Comments about this Internet Draft
should be sent to the dhcwg@ietf.org mailing list.
2. Revision history
Revision 00 to Revision 01
o Changed all occurrences of "suboption" to "option".
o Re-worded first sentence of Introduction to clarify that these
options are in wide use by PXE clients.
o Clarified external document references.
o Added description of site specific options 128 through 135.
o Added IANA Considerations and Security Considerations sections.
3. Option Definitions
There are three DHCP options [RFC2132]defined for use by PXE clients.
3.1 Client System Architecture Type Option Definition
The format of the option is:
Code Len 16-bit Type
+----+---+------+------+
| 93 | n | n1 | n2 |
+----+---+------+------+
Octet "n" MUST be an even number greater than zero. Clients that
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support more than one architecture type MAY include a list of these
types in their initial DHCP and PXE boot server packets. The list of
supported architecture types MAY be reduced in any packet exchange
between the client and server(s). Octets "n1" and "n2" encode a
16-bit architecture type identifier that describes the pre-boot
runtime environment(s) of the client machine.
As of the writing of this document the following pre-boot
architecture types have been requested.
Type Architecture Name
---- -----------------
0 Intel x86PC
1 NEC/PC98
2 EFI Itanium
3 DEC Alpha
4 Arc x86
5 Intel Lean Client
6 EFI IA32
This option must be present in all DHCP and PXE packets sent by PXE
compliant clients and servers.
3.2 Client Network Interface Identifier Option Definition
The format of the option is:
Code Len Type Major Minor
+----+-----+----+-----+-----+
| 94 | 3 | t | M | m |
+----+-----+----+-----+-----+
Octet "t" encodes a network interface type. For now the only
supported value is 1 for UNDI (Universal Network Device Interface).
Octets "M" and "m" describe the interface revision. To encode the
UNDI revision of 2.11, "M" would set to 2 and "m" would be set to 11
(0x0B).
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Revision Description
-------- -----------
< 2.00 LANDesk service agent boot ROMs. No PXE APIs.
2.00 First generation PXE boot ROMs. (PXENV+) [pxe]
2.01 Second generation PXE boot ROMs. (!PXE) [pxe]
3.00 32/64-bit UNDI specification. (Alpha) [efi]
EFI boot services driver only. No EFI runtime support.
3.10 32/64-bit UNDI specification. (Beta) [efi]
First generation EFI runtime driver support.
3.20 32/64-bit UNDI specification. (Release) [efi]
Second generation EFI runtime driver support.
This option must be present in all DHCP and PXE packets sent by PXE
compliant clients and servers.
3.3 Client Machine Identifier Option Definition
The format of the option is:
Code Len Type Machine Identifier
+----+-----+----+-----+ . . . +-----+
| 97 | n | t | | . . . | |
+----+-----+----+-----+ . . . +-----+
Octet "t" describes the type of the machine identifier in the
remaining octets in this option. 0 (zero) is the only defined value
for this octet at the present time and it describes the remaining
octets as a 16-octet GUID. Octet "n" is 17 for type 0. (One
definition of GUID can be found in Appendix A in the EFI
specification [efi].)
This option must be present in all DHCP and PXE packets sent by PXE
compliant clients and servers.
3.4 Site Specific Options Being Requested By PXE Client
All compliant PXE clients MUST include a request for DHCP options 128
through 135 in all DHCP and PXE packets. The format and contents of
these options are NOT defined by the PXE specification. These
options MAY be present in the DHCP and PXE boot server replies and
are meant for use by the downloaded network bootstrap programs.
These options are NOT used by the PXE boot ROMs.
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4. IANA Considerations
This document defines two new name spaces associated with PXE
compliant client machines: Client System Architecture Type and Client
Network Interface Identifier. IANA is requested to manage a registry
of values for these new name spaces, which are described in sections
2.1 and 2.2.
5. Security Considerations
This document in and by itself provides no security, nor does it
impact existing security.
6 Normative References
[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.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
[efi] Intel Corp., "Extensible Firmware Interface
Specification", December 2002.
http://developer.intel.com/technology/efi/main_specification.htm
[pxe] Henry, M. and M. Johnston, "Preboot Execution Environment
(PXE) Specification", September 1999.
ftp://download.intel.com/labs/manage/wfm/download/pxespec.pdf
Author's Address
Michael Johnston
Intel Corporation
MS. JF1-239 2111 NE 25th Ave.
Hillsboro, OR 97124
USA
Phone: +1 503-264-9703
EMail: michael.johnston@intel.com
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