Reclassifying Dynamic Host Configuration Protocol version 4 (DHCPv4) Options
RFC 3942
Document | Type |
RFC - Proposed Standard
(November 2004; Errata)
Updates RFC 2132
|
|
---|---|---|---|
Author | Bernie Volz | ||
Last updated | 2013-07-31 | ||
Stream | Internent Engineering Task Force (IETF) | ||
Formats | plain text html pdf htmlized (tools) htmlized bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 3942 (Proposed Standard) | |
Action Holders |
(None)
|
||
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Margaret Cullen | ||
Send notices to | rdroms@cisco.com |
Network Working Group B. Volz Request for Comments: 3942 Cisco Systems, Inc. Updates: 2132 November 2004 Category: Standards Track Reclassifying Dynamic Host Configuration Protocol version 4 (DHCPv4) Options Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2004). Abstract This document updates RFC 2132 to reclassify Dynamic Host 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 option codes available for assignment as publicly defined DHCP options for future options. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 2 3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 2 3.1. Publicly Defined Options Range . . . . . . . . . . . . . 2 3.2. Site-Specific Options Range . . . . . . . . . . . . . . 3 4. Reclassifying Options . . . . . . . . . . . . . . . . . . . . 3 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 8.1. Normative References . . . . . . . . . . . . . . . . . . 5 8.2. Informative References . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6 Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 7 Volz Standards Track [Page 1] RFC 3942 Reclassifying DHCPv4 Options November 2004 1. Introduction The DHCPv4 [RFC2131] publicly defined options range, options 1 - 127, is nearly used up. Efforts such as [RFC3679] help extend the life of this space, but ultimately the space will be exhausted. This document reclassifies much of the site-specific option range, which has not been widely used for its original intended purpose, to extend the publicly defined options space. 2. Requirements Notation 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 [RFC2119]. 3. Background The DHCP option space (0 - 255) is divided into two ranges [RFC2132]: 1. 1 - 127 are publicly defined options, now allocated in accordance with [RFC2939]. 2. 128 - 254 are site-specific options. Options 0 (pad) and 255 (end) are special and defined in [RFC2131]. 3.1. Publicly Defined Options Range The publicly defined options space (1 - 127) is nearly exhausted. Recent work [RFC3679] will buy more time, as several allocated but unused option codes have been reclaimed. A review could be made from time to time to determine whether there are other option codes that can be reclaimed. A longer-term solution to the eventual exhaustion of the publicly defined options space is desired. The DHC WG evaluated several solutions: 1. Using options 126 and 127 to carry 16-bit options as originally proposed by Ralph Droms in late 1996. However, this significantly penalizes the first option assigned to this new space, as it requires implementing the 16-bit option support. Because of this, options 126 and 127 have been reclaimed [RFC3679]. 2. Using a new magic cookie and 16-bit option code format. However, this proposal Volz Standards Track [Page 2] RFC 3942 Reclassifying DHCPv4 Options November 2004 * penalizes the first option assigned to this new space, as it requires significant changes to clients, servers, and relay agents, * could adversely impact existing clients, servers, and relay agents that fail to properly check the magic cookie value, * requires support of both message formats for the foreseeable future, and * requires clients to send multiple DHCPDISCOVER messages -- one for each magic cookie. 3. Reclassifying a portion of the site-specific option codes as publicly defined. The impact is minimal, as only those sitesShow full document text