draft-ietf-dhc-reclassify-options-01.txt   rfc3942.txt 
Network Working Group B. Volz Network Working Group B. Volz
Internet-Draft Cisco Systems, Inc. Request for Comments: 3942 Cisco Systems, Inc.
Expires: October 25, 2004 April 26, 2004 Updates: 2132 November 2004
Category: Standards Track
Reclassifying DHCPv4 Options Reclassifying Dynamic Host Configuration Protocol
draft-ietf-dhc-reclassify-options-01 version 4 (DHCPv4) Options
Status of this Memo Status of this Memo
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and any of which I become aware will be disclosed, in accordance with improvements. Please refer to the current edition of the "Internet
RFC 3668. Official Protocol Standards" (STD 1) for the standardization state
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved. Copyright (C) The Internet Society (2004).
Abstract Abstract
This document revises RFC 2132 to reclassify DHCPv4 option codes 128 This document updates RFC 2132 to reclassify Dynamic Host
to 223 (decimal) as publicly defined options to be managed by IANA in Configuration Protocol version 4 (DHCPv4) option codes 128 to 223
(decimal) as publicly defined options to be managed by IANA in
accordance with RFC 2939. This document directs IANA to make these accordance with RFC 2939. This document directs IANA to make these
option codes available for assignment as publicly defined DHCP option codes available for assignment as publicly defined DHCP
options for future options. options for future options.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 2
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3.1 Publicly Defined Options Range . . . . . . . . . . . . . . 3 3.1. Publicly Defined Options Range . . . . . . . . . . . . . 2
3.2 Site-Specific Options Range . . . . . . . . . . . . . . . 4 3.2. Site-Specific Options Range . . . . . . . . . . . . . . 3
4. Reclassifying Options . . . . . . . . . . . . . . . . . . . . 4 4. Reclassifying Options . . . . . . . . . . . . . . . . . . . . 3
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1 Normative References . . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . 5
8.2 Informative References . . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . . 8 Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction 1. Introduction
The DHCPv4 [RFC2131] publicly defined options range, options 1-127, The DHCPv4 [RFC2131] publicly defined options range, options 1-127,
is nearly used up. Efforts such as [RFC3679] help extend the life of is nearly used up. Efforts such as [RFC3679] help extend the life of
this space, but ultimately the space is expected to be exhausted. this space, but ultimately the space will be exhausted.
This document reclassifies much of the site-specific option range, This document reclassifies much of the site-specific option range,
which has not been widely used for its original intended purpose, to which has not been widely used for its original intended purpose, to
extend the publicly defined options space. extend the publicly defined options space.
2. Requirements notation 2. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
3. Background 3. Background
The DHCP option space (0-255) is divided into two ranges [RFC2132]: The DHCP option space (0-255) is divided into two ranges [RFC2132]:
1. 1-127 are publicly defined options, now allocated in accordance 1. 1-127 are publicly defined options, now allocated in accordance
with [RFC2939]. with [RFC2939].
2. 128-254 are site-specific options. 2. 128-254 are site-specific options.
Options 0 (pad) and 255 (end) are special and defined in [RFC2131]. Options 0 (pad) and 255 (end) are special and defined in [RFC2131].
3.1 Publicly Defined Options Range 3.1. Publicly Defined Options Range
The publicly defined options space (1-127) is nearly exhausted. The publicly defined options space (1-127) is nearly exhausted.
Recent work ([RFC3679]) will buy more time as several allocated but Recent work [RFC3679] will buy more time, as several allocated but
never used option codes are reclaimed. And, a review could be done unused option codes have been reclaimed. A review could be made from
from time to time to determine if there are other option codes that time to time to determine whether there are other option codes that
can be reclaimed. can be reclaimed.
A longer term solution to the eventual exhaustion of the publicly A longer-term solution to the eventual exhaustion of the publicly
defined options space is desired. The DHC WG evaluated several defined options space is desired. The DHC WG evaluated several
solutions: solutions:
1. Using options 126 and 127 to carry 16-bit options as originally 1. Using options 126 and 127 to carry 16-bit options as originally
proposed by Ralph Droms in late 1996. However, this significantly proposed by Ralph Droms in late 1996. However, this significantly
penalizes the first option assigned to this new space, as it penalizes the first option assigned to this new space, as it
requires implementing the 16-bit option support. Because of this, requires implementing the 16-bit option support. Because of this,
options 126 and 127 have been reclaimed [RFC3679]. options 126 and 127 have been reclaimed [RFC3679].
2. Using a new magic cookie and 16-bit option code format. However, 2. Using a new magic cookie and 16-bit option code format. However,
this proposal: this proposal
* penalizes the first option assigned to this new space, as it * penalizes the first option assigned to this new space, as it
requires significant changes to clients, servers, and relay requires significant changes to clients, servers, and relay
agents, agents,
* could adversely impact existing clients, servers, and relay * could adversely impact existing clients, servers, and relay
agents that fail to properly check the magic cookie value, agents that fail to properly check the magic cookie value,
* requires support of both message formats for the foreseeable * requires support of both message formats for the foreseeable
future, and future, and
* requires clients to send multiple DHCPDISCOVER messages - one
* requires clients to send multiple DHCPDISCOVER messages -- one
for each magic cookie. for each magic cookie.
3. Reclassifying a portion of the site-specific option codes as 3. Reclassifying a portion of the site-specific option codes as
publicly defined. The impact is minimal as only those sites publicly defined. The impact is minimal, as only those sites
presently using options in the reclassified range need to presently using options in the reclassified range need to renumber
renumber their options. their options.
3.2 Site-Specific Options Range 3.2. Site-Specific Options Range
The site-specific option range is rather large (127 options in all) The site-specific option range is rather large (127 options in all)
and has been little used. The original intent of the site-specific and little used. The original intent of the site-specific option
option range was to support local (to a site) configuration options, range was to support local (to a site) configuration options, and it
and it is difficult to believe a site would need 127 options for this is difficult to believe a site would need 127 options for this
purpose. Further, many DHCP client implementations do not provide a purpose. Further, many DHCP client implementations do not provide a
well documented means of requesting site-specific options from a well documented means to request site-specific options from a server
server or allowing applications to extract the returned option or to allow applications to extract the returned option values.
values.
Some vendors have made use of site-specific option codes that violate Some vendors have made use of site-specific option codes that violate
the intent of the site-specific options, as the options are used to the intent of the site-specific options, as the options are used to
configure features of their products and thus are specific to many configure features of their products and thus are specific to many
sites. This usage can potentially cause problems if a site has been sites. This usage could potentially cause problems if a site that
using the same site-specific option codes for other purposes and then has been using the same site-specific option codes for other purposes
deploys products from one of the vendors or if two vendors pick the deploys products from one of the vendors, or if two vendors pick the
same site-specific options. same site-specific options.
4. Reclassifying Options 4. Reclassifying Options
The site-specific option codes 128 to 223 are hereby reclassified as The site-specific option codes 128 to 223 are hereby reclassified as
publicly defined options. This leaves 31 site-specific options, 224 publicly defined options. This leaves 31 site-specific options, 224
to 254. to 254.
To allow vendors that have made use of site-specific options within To allow vendors that have made use of site-specific options within
the reclassified range to publicly document their option usage and the reclassified range to publish their option usage and to request
request an official assignment of the option number to that usage, an official assignment of the option number to that usage, the
the following procedure will be used to reclassify these options: following procedure will be used to reclassify these options:
1. The reclassified options (128 to 223) will be placed in the 1. The reclassified options (128 to 223) will be placed in the
"Unavailable" state by IANA. These options are not yet available "Unavailable" state by IANA. These options are not yet available
for assignment to publicly defined options. for assignment to publicly defined options.
2. Vendors that currently use one or more of the reclassified 2. Vendors that currently use one or more of the reclassified options
options have until 6 months after this RFC's publication date to have 6 months following this RFC's publication date to notify the
notify the DHC WG and IANA that they are using particular options DHC WG and IANA that they are using particular options numbers and
numbers and agree to document that usage in an RFC. IANA will agree to document that usage in an RFC. IANA will move these
move these options from the "Unavailable" to options from the "Unavailable" to "Tentatively Assigned" state.
"Tentatively-Assigned" state.
Vendors have 18 months from this RFC's publication date to start Vendors have 18 months from this RFC's publication date to start
the documentation process by submitting an Internet-Draft. the documentation process by submitting an Internet-Draft.
NOTE: If multiple vendors of an option number come forward and NOTE: If multiple vendors of an option number come forward and can
can demonstrate their usage is in reasonably wide use, none of demonstrate that their usage is in reasonably wide use, none of
the vendors will be allowed to keep the current option number and the vendors will be allowed to keep the current option number, and
they MUST go through the normal process of getting a publicly they MUST go through the normal process of getting a publicly
assigned option [RFC2939]. assigned option [RFC2939].
3. Any options still classified as "Unavailable" 6 months after the 3. Any options still classified as "Unavailable" 6 months after the
RFC publication date will be moved to the "Unassigned" state by RFC publication date will be moved to the "Unassigned" state by
IANA. These options may then be assigned to any new publicly IANA. These options may then be assigned to any new publicly
defined options in accordance with [RFC2939]. defined options in accordance with [RFC2939].
4. For those options in the "Tentatively-Assigned" state, vendors 4. For those options in the "Tentatively Assigned" state, vendors
have until 18 months from this RFC's publication date to submit have 18 months following this RFC's publication date to submit an
an Internet-Draft documenting the option. The documented usage Internet-Draft documenting the option. The documented usage MUST
MUST be consistent with the existing usage. When the option usage be consistent with the existing usage. When the option usage is
is published as an RFC, IANA will move the option to the published as an RFC, IANA will move the option to the "Assigned"
"Assigned" state. state.
If no Internet-Draft is published within the 18 months or should If no Internet-Draft is published within the 18 months or should
one of these Internet-Drafts expire after the 18 months, IANA one of these Internet-Drafts expire after the 18 months, IANA will
will move the option to the "Unassigned" state and the option may move the option to the "Unassigned" state, and the option may then
then be assigned to any new publicly defined options in be assigned to any new publicly defined options in accordance with
accordance with [RFC2939]. [RFC2939].
Sites that are presently using site-specific option codes within the Sites presently using site-specific option codes within the
reclassified range SHOULD take steps to renumber these options to reclassified range SHOULD take steps to renumber these options to
values within the remaining range. If a site needs more than 31 values within the remaining range. If a site needs more than 31
site-specific options, the site must switch to using suboptions as site-specific options, the site must switch to using suboptions, as
has been done for other options, such as the Relay Agent Information has been done for other options, such as the Relay Agent Information
Option [RFC3046]. Option [RFC3046].
5. Security Considerations 5. Security Considerations
This document in and by itself provides no security, nor does it This document in and by itself provides no security, nor does it
impact existing DCHP security as described in [RFC2131]. impact existing DCHP security as described in [RFC2131].
6. IANA Considerations 6. IANA Considerations
IANA is requested to: IANA is requested to
1. Expand the publicly defined DHCPv4 options space from 1-127 to 1. expand the publicly defined DHCPv4 options space from 1 - 127 to 1
1-223. The new options (128-223) are to be listed as - 223. The new options (128 - 223) are to be listed as
"Unavailable" and MUST NOT be assigned to any publicly defined "Unavailable" and MUST NOT be assigned to any publicly defined
options. options.
2. Receive notices from vendors that have been using one or more of
2. receive notices from vendors that have been using one or more of
the options in the 128-223 range that they are using the option the options in the 128-223 range that they are using the option
and are willing to document that usage. IANA will list these and are willing to document that usage. IANA will list these
options as "Tentatively-Assigned". options as "Tentatively Assigned".
3. 6 months from this RFC's publication date, change the listing of
any options listed as "Unavailable" to "Available". These options 3. change the listing of any options listed as "Unavailable" to
may now be assigned in accordance with [RFC2939]. "Available" 6 months from this RFC's publication date. These
4. 18 months from this RFC's publication date and periodically options may now be assigned in accordance with [RFC2939].
thereafter as long as there is an option listed as
"Tentatively-Assigned", change the listing of any options listed 4. change the listing of any options listed as "Tentatively-Assigned"
as "Tentatively-Assigned" to "Unavailable" if no un-expired to "Unavailable" 18 months from this RFC's publication date and
Internet-Draft exists documenting the usage. periodically thereafter as long as there is an option listed as
"Tentatively-Assigned", if no un-expired Internet-Draft exists
documenting the usage.
7. Acknowledgements 7. Acknowledgements
Many thanks to Ralph Droms and Ted Lemon for their valuable input and Many thanks to Ralph Droms and Ted Lemon for their valuable input and
earlier work on the various alternatives. earlier work on the various alternatives.
8. References 8. References
8.1 Normative References 8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, March 1997. 2131, March 1997.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor [RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997. Extensions", RFC 2132, March 1997.
[RFC2939] Droms, R., "Procedures and IANA Guidelines for Definition [RFC2939] Droms, R., "Procedures and IANA Guidelines for Definition
of New DHCP Options and Message Types", BCP 43, RFC 2939, of New DHCP Options and Message Types", BCP 43, RFC 2939,
September 2000. September 2000.
8.2 Informative References 8.2. Informative References
[RFC3046] Patrick, M., "DHCP Relay Agent Information Option", RFC [RFC3046] Patrick, M., "DHCP Relay Agent Information Option", RFC
3046, January 2001. 3046, January 2001.
[RFC3679] Droms, R., "Unused Dynamic Host Configuration Protocol [RFC3679] Droms, R., "Unused Dynamic Host Configuration Protocol
(DHCP) Option Codes", RFC 3679, January 2004. (DHCP) Option Codes", RFC 3679, January 2004.
Author's Address Author's Address
Bernard Volz Bernard Volz
Cisco Systems, Inc. Cisco Systems, Inc.
1414 Massachusetts Ave. 1414 Massachusetts Ave.
Boxborough, MA 01719 Boxborough, MA 01719
USA USA
Phone: +1 978 936 0382 Phone: +1 978 936 0382
EMail: volz@cisco.com EMail: volz@cisco.com
Intellectual Property Statement Full Copyright Statement
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This document is subject to the rights, licenses and restrictions
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This document and the information contained herein are provided on an
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ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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Copyright (C) The Internet Society (2004). This document is subject
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Internet Society. Internet Society.
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