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Versions: 00 01 02 03 RFC 4578

Dynamic Host Configuration Working                           M. Johnston
Group                                                  Intel Corporation
Internet-Draft                                            S. Venaas, Ed.
Expires: April 29, 2006                        University of Southampton
                                                        October 26, 2005


            DHCP Preboot eXecution Environment (PXE) Options
                     draft-ietf-dhc-pxe-options-02

Status of this Memo

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   We define DHCP options being used by PXE and EFI clients to uniquely
   identify booting client machines 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.

Requirements Language



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   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 [1].


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Revision history  . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Option Definitions  . . . . . . . . . . . . . . . . . . . . . . 4
     3.1.  Client System Architecture Type Option Definition . . . . . 4
     3.2.  Client Network Interface Identifier Option Definition . . . 4
     3.3.  Client Machine Identifier Option Definition . . . . . . . . 5
     3.4.  Options Requested by PXE Clients  . . . . . . . . . . . . . 5
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   7.  Normative References  . . . . . . . . . . . . . . . . . . . . . 6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 7
   Intellectual Property and Copyright Statements  . . . . . . . . . . 8































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1.  Introduction

   These DHCP [2] options 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 [3] and EFI
   [4] 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 use of options 128 through 135.

   o  Added IANA Considerations and Security Considerations sections.

   Revision 01 to Revision 02

   o  Changed and extended description of use of options 128 through
      135.

   o  Removed text on IANA registries since Informational.







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3.  Option Definitions

   There are three DHCP options [5] 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
   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).



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   Octets "M" and "m" describe the interface revision.  To encode the
   UNDI revision of 2.11, "M" would be set to 2 and "m" would be set to
   11 (0x0B).

      Revision  Description
      --------  -----------
      < 2.00    LANDesk service agent boot ROMs.  No PXE APIs.

        2.00    First generation PXE boot ROMs.  (PXENV+)  [3]

        2.01    Second generation PXE boot ROMs.  (!PXE)   [3]

        3.00    32/64-bit UNDI specification.  (Alpha)     [4]
                EFI boot services driver only.  No EFI runtime support.

        3.10    32/64-bit UNDI specification.  (Beta)  [4]
                First generation EFI runtime driver support.

        3.20    32/64-bit UNDI specification.  (Release)  [4]
                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.  Options Requested by PXE Clients

   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



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   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.

   As options 128-135 are not officially assigned for PXE use (previous
   to November 2004 they were considered site-specific options, [6]),
   use of these options may conflict with other uses of these options.


4.  Acknowledgements

   The authors thank Bernie Volz for valuable input.


5.  IANA Considerations

   This document has no actions for IANA.


6.  Security Considerations

   This document in and by itself provides no security, nor does it
   impact existing security.

7.  Normative References

   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [2]  Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
        March 1997.

   [3]  Henry, M. and M. Johnston, "Preboot Execution Environment (PXE)
        Specification", September 1999,
        <http://www.pix.net/software/pxeboot/archive/pxespec.pdf>.

   [4]  Intel Corp., "Extensible Firmware Interface Specification",
        December 2002, <http://developer.intel.com/technology/efi/
        main_specification.htm>.

   [5]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
        Extensions", RFC 2132, March 1997.

   [6]  Volz, B., "Reclassifying Dynamic Host Configuration Protocol
        version 4 (DHCPv4) Options", RFC 3942, November 2004.






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Authors' Addresses

   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


   Stig Venaas
   University of Southampton
   School of Electronics and Computer Science
   Southampton, Hampshire  SO17 1BJ
   United Kingdom

   Email: sv@ecs.soton.ac.uk
































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