Dynamic Host Configuration Protocol (DHCP) Options for the Intel Preboot eXecution Environment (PXE)
The information below is for an old version of the document that is already published as an RFC.
This is an older version of an Internet-Draft that was ultimately published as RFC 4578.
|Authors||Michael O. Johnston , Stig Venaas|
|Last updated||2020-01-21 (Latest revision 2006-03-20)|
|RFC stream||Internet Engineering Task Force (IETF)|
|Additional resources||Mailing list discussion|
|IESG||IESG state||RFC 4578 (Informational)|
|Responsible AD||Margaret Cullen|
|Send notices firstname.lastname@example.org|
Dynamic Host Configuration Working M. Johnston Group Intel Corporation Internet-Draft S. Venaas, Ed. Expires: September 8, 2006 UNINETT March 7, 2006 DHCP Options for the Intel Preboot eXecution Environment (PXE) draft-ietf-dhc-pxe-options-03 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on September 8, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract We define DHCP options being used by Preboot eXecution Environment (PXE) and Extensible Firmware Interface (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. Johnston & Venaas, Ed. Expires September 8, 2006 [Page 1] Internet-Draft DHCP PXE Options March 2006 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 . Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Option Definitions . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Client System Architecture Type Option Definition . . . . . 3 2.2. Client Network Interface Identifier Option Definition . . . 4 2.3. Client Machine Identifier Option Definition . . . . . . . . 5 2.4. Options Requested by PXE Clients . . . . . . . . . . . . . 5 3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 6. Normative References . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Intellectual Property and Copyright Statements . . . . . . . . . . 8 Johnston & Venaas, Ed. Expires September 8, 2006 [Page 2] Internet-Draft DHCP PXE Options March 2006 1. Introduction These DHCP  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 by Intel in the PXE  and EFI  specifications and are being documented in this draft for completeness within the IETF. 2. Option Definitions There are three DHCP options  defined for use by PXE clients. 2.1. Client System Architecture Type Option Definition The format of the option is: Code Len 16-bit Type +----+-----+-----+-----+ | 93 | n | n1 | n2 | +----+-----+-----+-----+ Octet "n" gives the number of octets containing "architecture types" (not including the code and len fields). It 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. Johnston & Venaas, Ed. Expires September 8, 2006 [Page 3] Internet-Draft DHCP PXE Options March 2006 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. 2.2. 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 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+)  2.01 Second generation PXE boot ROMs. (!PXE)  3.00 32/64-bit UNDI specification. (Alpha)  EFI boot services driver only. No EFI runtime support. 3.10 32/64-bit UNDI specification. (Beta)  First generation EFI runtime driver support. 3.20 32/64-bit UNDI specification. (Release)  Second generation EFI runtime driver support. Johnston & Venaas, Ed. Expires September 8, 2006 [Page 4] Internet-Draft DHCP PXE Options March 2006 This option MUST be present in all DHCP and PXE packets sent by PXE compliant clients and servers. 2.3. 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. 2.4. 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 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, ), use of these option values for PXE may conflict with other uses of the same options on the same networks. 3. Acknowledgements The authors thank Bernie Volz for valuable input. 4. IANA Considerations IANA is requested to update the numbering space defined for public DHCP options in  with references to this document for options 93, 94 and 97 (currently there are references to ), and also mark options 128-135 as being used by PXE and reference this document Johnston & Venaas, Ed. Expires September 8, 2006 [Page 5] Internet-Draft DHCP PXE Options March 2006 (they are currently marked as being used by PXE, but without references). 5. Security Considerations By specifying incorrect values for some of these options a client may get access to, and possibly attempt to execute, code intended for another platform or client. This may have security ramifications. Also note that these options contain information about a client's system architecture and pre-OS runtime environment which is revealed to anyone who is able to listen in on DHCP messages sent by the client. This information may be of use to potential attackers. 6. Normative References  Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.  Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997.  Henry, M. and M. Johnston, "Preboot Execution Environment (PXE) Specification", September 1999, <http://www.pix.net/software/pxeboot/archive/pxespec.pdf>.  Intel Corp., "Extensible Firmware Interface Specification", December 2002, <http://developer.intel.com/technology/efi/ main_specification.htm>.  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor Extensions", RFC 2132, March 1997.  Volz, B., "Reclassifying Dynamic Host Configuration Protocol version 4 (DHCPv4) Options", RFC 3942, November 2004.  Droms, R., "Procedures and IANA Guidelines for Definition of New DHCP Options and Message Types", BCP 43, RFC 2939, September 2000.  Droms, R., "Unused Dynamic Host Configuration Protocol (DHCP) Option Codes", RFC 3679, January 2004. Johnston & Venaas, Ed. Expires September 8, 2006 [Page 6] Internet-Draft DHCP PXE Options March 2006 Authors' Addresses Michael Johnston Intel Corporation MS. JF1-239 2111 NE 25th Ave. Hillsboro, OR 97124 USA Phone: +1 503-264-9703 Email: email@example.com Stig Venaas UNINETT Trondheim NO-7465 Norway Email: firstname.lastname@example.org Johnston & Venaas, Ed. Expires September 8, 2006 [Page 7] Internet-Draft DHCP PXE Options March 2006 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. 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Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Johnston & Venaas, Ed. Expires September 8, 2006 [Page 8]