Network Working Group R. Droms
INTERNET-DRAFT Bucknell University
Obsoletes: draft-ietf-dhc-new-options-01.txt August 1998
Expires February 1999
Procedure for Defining New DHCP Options
<draft-ietf-dhc-new-options-02.txt>
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Abstract
The Dynamic Host Configuration Protocol (DHCP) provides a framework
for passing configuration information to hosts on a TCP/IP network.
Configuration parameters and other control information are carried in
tagged data items that are stored in the 'options' field of the DHCP
message. The data items themselves are also called 'options.'
New DHCP options may be defined after the publication of the DHCP
specification to accommodate requirements for conveyance of new
configuration parameters. This document describes the procedure for
defining new DHCP options.
Introduction
The Dynamic Host Configuration Protocol (DHCP) [1] provides a
framework for passing configuration information to hosts on a TCP/IP
network. Configuration parameters and other control information are
carried in tagged data items that are stored in the 'options' field
of the DHCP message. The data items themselves are also called
"options." [2]
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This document describes the procedure for defining new DHCP options.
The procedure will guarantee that:
* allocation of new option numbers is coordinated from a single
authority,
* new options are reviewed for technical correctness and
appropriateness, and
* documentation for new options is complete and published.
As indicated in "Guidelines for Writing an IANA Considerations
Section in RFCs" [3], IANA acts as a central authority for assignment
of numbers for new DHCP options. The new procedure outlined in this
document will provide guidance to IANA in the assignment of new
option numbers.
Overview and background
The procedure described in this document modifies and clarifies the
procedure for defining new options in RFC 2131 [2]. The primary
modification is to the time at which a new DHCP option is assigned an
option number. In the procedure described in this document, the
option number is not assigned until after the option has been
accepted as an Internet Standard and the specification is about to be
published as an RFC.
DISCUSSION:
Since the publication of RFC 2132, the option number space for
publically defined DHCP options (1-127) has almost been exhausted.
Many of the defined option numbers have not been followed up with
Internet Drafts submitted to the DHC WG. There has been a lack of
specific guidance to IANA from the DHC WG as to the assignment of
DHCP option numbers
The procedure as specified in RFC 2132 does not clearly state that
new options are to be reviewed individually for acceptance as
Internet Standards and that the specifications for newly accepted
Standard options are to be published as separate RFCs. RFC 2132
also does not require that new options are to be submitted to the
DHC WG through the WG chair, and that the author of the option
specification is responsible for bringing new options to the
attention of the WG chair for WG review. Finally, RFC 2132 does
not make clear that newly defined options are not to be
incorporated into products, included in other specifications or
otherwise used until accepted as Internet Standards.
The Internet Standard DHCP options assigned as of March 1997 are
defined in RFC 2132. In the future, new DHCP options will be
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reviewed individually by the DHC WG and the IETF for acceptance as
Internet Standards and the specifications will be published as
separate RFCs. Groups of related options may be combined into a
single specification and reviewed as a set by the DHC WG. Prior to
acceptance as an Internet Standard, it is not appropriate to
incorporate new options into products, include the specification in
other documents or otherwise make use of the new options.
DISCUSSION:
While the last statement is strong, if it is not included the IETF
may be presented with a "fait accompli" in which a new option is
defined and shipped prior to review by the WG.
The DHCP option number space (1-254) is split into two parts. The
site-specific options (128-254) are defined as "Private Use" and
require no review by the DHC WG. The public options (1-127) are
defined as "Specification Required" and new options must be reviewed
prior to assignment of an option number by IANA. The details of the
review process are given in the following section of this document.
Procedure
The author of a new DHCP option will follow these steps to obtain
acceptance of the option as a part of the DHCP Internet Standard:
1. The author devises the new option.
2. The author documents the new option, leaving the option code as
"To Be Determined" (TBD), as an Internet Draft.
DISCUSSION:
The requirement that the new option be documented as an
Internet Draft is a matter of expediency. In theory, the new
option could be documented on the back of an envelope for
submission; as a practical matter, the specification will
eventually become an Internet Draft as part of the review
process.
3. The author submits the Internet Draft for review through the IETF
standards process as defined in "Internet Official Protocol
Standards" (STD 1) [4] and "Internet Standards Process" (BCP 9)
[6].
DISCUSSION:
Note that simply publishing the new option as an Internet Draft
does not automatically enter the option into the Standards
Track. The author of the new option must explicitly forward a
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DRAFT Procedure for Defining New DHCP Options August 1998
request for action on the new option to the DHC WG or the IESG.
4. The new option progresses through the IETF standards process. The
specification of the new option is reviewed by the DHC WG (if it
exists) or by the IETF. The option is considered for acceptance
as an Internet Standard. If the option is accepted as a Standard,
the specification for the option is published as a separate RFC.
5. At the time of acceptance as an Internet Standard and publication
as an RFC, IANA assigns a DHCP option number to the new option.
References
[1] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, Bucknell
University, March 1997.
[2] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, Lachman Associates, March 1997.
[3] Narten, T. and H. T. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", (work in progress), May 1998.
[4] Postel, J. (Ed.), "Internet Official Protocol Standards", STD 1, May
1998.
[5] Droms, R. and K. Fong, "NetWare/IP Domain Name and Information", RFC
2142, November 1997.
[6] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9,
October, 1996.
Security Considerations
Information that creates or updates an option number assignment needs
to be authenticated.
An analysis of security issues is required for all newly defined DHCP
options. The description of security issues in the specification of
new options must be as accurate as possible. The specification for a
new option may reference the "Security Considerations" section in the
DHCP specification [1]; e.g. (from "NetWare/IP Domain Name and
Information" [5]):
DHCP currently provides no authentication or security mechanisms.
Potential exposures to attack are discussed in section 7 of the
DHCP protocol specification [RFC 2131].
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Author's Address
Ralph Droms
Computer Science Department
323 Dana Engineering
Bucknell University
Lewisburg, PA 17837
Phone: (717) 524-1145
EMail: droms@bucknell.edu
Expiration
This document will expire on February 2, 1999.
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DRAFT Procedure for Defining New DHCP Options August 1998
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