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Network Working Group                                          T. NartenRequest for Comments: 2434                                           IBMBCP: 26                                                    H. AlvestrandCategory: Best Current Practice                                  Maxware                                                            October 1998Guidelines for Writing an IANA Considerations Section in RFCsStatus of this Memo   This document specifies an Internet Best Current Practices for the   Internet Community, and requests discussion and suggestions for   improvements.  Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (1998).  All Rights Reserved.Abstract   Many protocols make use of identifiers consisting of constants and   other well-known values. Even after a protocol has been defined and   deployment has begun, new values may need to be assigned (e.g., for a   new option type in DHCP, or a new encryption or authentication   algorithm for IPSec).  To insure that such quantities have consistent   values and interpretations in different implementations, their   assignment must be administered by a central authority. For IETF   protocols, that role is provided by the Internet Assigned Numbers   Authority (IANA).   In order for the IANA to manage a given name space prudently, it   needs guidelines describing the conditions under which new values can   be assigned. If the IANA is expected to play a role in the management   of a name space, the IANA must be given clear and concise   instructions describing that role.  This document discusses issues   that should be considered in formulating a policy for assigning   values to a name space and provides guidelines to document authors on   the specific text that must be included in documents that place   demands on the IANA.Narten & Alvestrand      Best Current Practice                  [Page 1]

RFC 2434           Guidelines for IANA Considerations       October 1998Table of Contents   Status of this Memo..........................................11.  Introduction.............................................22.  Issues To Consider.......................................33.  Registration maintenance.................................64.  What To Put In Documents.................................75.  Applicability to Past and Future RFCs....................86.  Security Considerations..................................87.  Acknowledgments..........................................98.  References...............................................99.  Authors' Addresses.......................................1010. Full Copyright Statement.................................111.  Introduction   Many protocols make use of fields that contain constants and other   well-known values (e.g., the Protocol field in the IP header [IP] or   MIME types in mail messages [MIME-REG]). Even after a protocol has   been defined and deployment has begun, new values may need to be   assigned (e.g., a new option type in DHCP [DHCP] or a new encryption   or authentication algorithm for IPSec [IPSEC]).  To insure that such   fields have consistent values and interpretations in different   implementations, their assignment must be administered by a central   authority. For IETF protocols, that role is provided by the Internet   Assigned Numbers Authority (IANA).   In this document, we call the set of possible values for such a field   a "name space"; its actual content may be a name, a number or another   kind of value. The assignment of a specific value to a name space is   called an assigned number (or assigned value). Each assignment of a   number in a name space is called a registration.   In order for the IANA to manage a given name space prudently, it   needs guidelines describing the conditions under which new values   should be assigned. This document provides guidelines to authors on   what sort of text should be added to their documents, and reviews   issues that should be considered in formulating an appropriate policy   for assigning numbers to name spaces.   Not all name spaces require centralized administration.  In some   cases, it is possible to delegate a name space in such a way that   further assignments can be made independently and with no further   (central) coordination. In the Domain Name System, for example, the   IANA only deals with assignments at the higher-levels, while   subdomains are administered by the organization to which the space   has been delegated. As another example, Object Identifiers (OIDs) as   defined by the ITU are also delegated [ASSIGNED].  When a name spaceNarten & Alvestrand      Best Current Practice                  [Page 2]

RFC 2434           Guidelines for IANA Considerations       October 1998   can be delegated, the IANA only deals with assignments at the top   level.   This document uses the terms 'MUST', 'SHOULD' and 'MAY', and their   negatives, in the way described inRFC 2119 [KEYWORDS]. In this case,   "the specification" as used byRFC 2119 refers to the processing of   protocols being submitted to the IETF standards process.2.  Issues To Consider   The primary issue to consider in managing a name space is its size.   If the space is small and limited in size, assignments must be made   carefully to insure that the space doesn't become exhausted. If the   space is essentially unlimited, on the other hand, it may be   perfectly reasonable to hand out new values to anyone that wants one.   Even when the space is essentially unlimited, however, it is usually   desirable to have a minimal review to prevent the hoarding of or   unnecessary wasting of a space. For example, if the space consists of   text strings, it may be desirable to prevent organizations from   obtaining large sets of strings that correspond to the "best" names   (e.g., existing company names).   A second consideration is whether it makes sense to delegate the name   space in some manner. This route should be pursued when appropriate,   as it lessens the burden on the IANA for dealing with assignments.   In some cases, the name space is essentially unlimited, and assigned   numbers can safely be given out to anyone. When no subjective review   is needed, the IANA can make assignments directly, provided that the   IANA is given specific instructions on what types of requests it   should grant, and what information must be provided before a request   for an assigned number will be considered. Note that the IANA will   not define an assignment policy; it should be given a set of   guidelines that allow it to make allocation decisions with little   subjectivity.   In most cases, some review of prospective allocations is appropriate,   and the question becomes who should perform the review and how   rigorous the review needs to be.  In many cases, one might think that   an IETF Working Group (WG) familiar with the name space at hand   should be consulted. In practice, however, WGs eventually disband, so   they cannot be considered a permanent evaluator. It is also possible   for name spaces to be created through individual submission   documents, for which no WG is ever formed.   One way to insure community review of prospective assignments is to   have the requester submit a document for publication as an RFC. Such   an action insures that the IESG and relevant WGs review theNarten & Alvestrand      Best Current Practice                  [Page 3]

RFC 2434           Guidelines for IANA Considerations       October 1998   assignment. This is the preferred way of insuring review, and is   particularly important if any potential interoperability issues can   arise. For example, many assignments are not just assignments, but   also involve an element of protocol specification. A new option may   define fields that need to be parsed and acted on, which (if   specified poorly) may not fit cleanly with the architecture of other   options or the base protocols on which they are built.   In some cases, however, the burden of publishing an RFC in order to   get an assignment is excessive. However, it is generally still useful   (and sometimes necessary) to discuss proposed additions on a mailing   list dedicated to the purpose (e.g., the ietf-types@iana.org for   media types) or on a more general mailing list (e.g., that of a   current or former IETF WG).  Such a mailing list provides a way for   new registrations to be publicly reviewed prior to getting assigned,   or to give advice for persons who want help in understanding what a   proper registration should contain.   While discussion on a mailing list can provide valuable technical   expertise, opinions may vary and discussions may continue for some   time without resolution.  In addition, the IANA cannot participate in   all of these mailing lists and cannot determine if or when such   discussions reach consensus.  Therefore, the IANA cannot allow   general mailing lists to fill the role of providing definitive   recommendations regarding a registration question.  Instead, the IANA   will use a designated subject matter expert.  The IANA will rely on a   "designated expert" to advise it in assignment matters.  That is, the   IANA forwards the requests it receives to a specific point-of-contact   (one or a small number of individuals) and acts upon the returned   recommendation from the designated expert. The designated expert can   initiate and coordinate as wide a review of an assignment request as   may be necessary to evaluate it properly.   Designated experts are appointed by the relevant Area Director of the   IESG. They are typically named at the time a document that creates a   new numbering space is published as an RFC, but as experts originally   appointed may later become unavailable, the relevant Area Director   will appoint replacements if necessary.   Any decisions made by the designated expert can be appealed using the   normal IETF appeals process as outlined inSection 6.5 of [IETF-   PROCESS]. Since the designated experts are appointed by the IESG,   they may be removed by the IESG.Narten & Alvestrand      Best Current Practice                  [Page 4]

RFC 2434           Guidelines for IANA Considerations       October 1998   The following are example policies, some of which are in use today:      Private Use - For private or local use only, with the type and           purpose defined by the local site. No attempt is made to           prevent multiple sites from using the same value in different           (and incompatible) ways. There is no need for IANA to review           such assignments and assignments are not generally useful for           interoperability.           Examples: Site-specific options in DHCP [DHCP] have           significance only within a single site.  "X-foo:" header           lines in email messages.      Hierarchical allocation - Delegated managers can assign values           provided they have been given control over that part of the           name space.  IANA controls the higher levels of the namespace           according to one of the other policies.           Examples: DNS names, Object Identifiers      First Come First Served - Anyone can obtain an assigned number, so           long as they provide a point of contact and a brief           description of what the value would be used for.  For           numbers, the exact value is generally assigned by the IANA;           with names, specific names are usually requested.           Examples: vnd. (vendor assigned) MIME types [MIME-REG], TCP           and UDP port numbers.      Expert Review - approval by a Designated Expert is required.      Specification Required - Values and their meaning must be           documented in an RFC or other permanent and readily available           reference, in sufficient detail so that interoperability           between independent implementations is possible.           Examples: SCSP [SCSP]      IESG Approval - New assignments must be approved by the IESG, but           there is no requirement that the request be documented in an           RFC (though the IESG has discretion to request documents or           other supporting materials on a case-by-case basis).Narten & Alvestrand      Best Current Practice                  [Page 5]

RFC 2434           Guidelines for IANA Considerations       October 1998      IETF Consensus - New values are assigned through the IETF           consensus process. Specifically, new assignments are made via           RFCs approved by the IESG. Typically, the IESG will seek           input on prospective assignments from appropriate persons           (e.g., a relevant Working Group if one exists).           Examples: SMTP extensions [SMTP-EXT], BGP Subsequent Address           Family Identifiers [BGP4-EXT].      Standards Action - Values are assigned only for Standards Track           RFCs approved by the IESG.           Examples: MIME top level types [MIME-REG]   It should be noted that it often makes sense to partition a name   space into several categories, with assignments out of each category   handled differently. For example, the DHCP option space [DHCP] is   split into two parts. Option numbers in the range of 1-127 are   globally unique and assigned according to the Specification Required   policy described above, while options number 128-254 are "site   specific", i.e., Local Use. Dividing the name space up makes it   possible to allow some assignments to be made with minimal review,   while simultaneously reserving some part of the space for future use.3.  Registration maintenance   Registrations are a request for an assigned number, including the   related information needed to evaluate and document the request. Even   after a number has been assigned, some types of registrations contain   additional information that may need to be updated over time. For   example, mime types, character sets, language tags, etc. typically   include more information than just the registered value itself.   Example information can include point of contact information,   security issues, pointers to updates, literature references, etc.  In   such cases, the document must clearly state who is responsible for   maintaining and updating a registration. It is appropriate to:      - Let the author update the registration, subject to the same        constraints and review as with new registrations.      - Allow some mechanism to attach comments to the registration, for        cases where others have significant objections to claims in a        registration, but the author does not agree to change the        registration.Narten & Alvestrand      Best Current Practice                  [Page 6]

RFC 2434           Guidelines for IANA Considerations       October 1998      - Designate the IESG or another authority as having the right to        reassign ownership of a registration. This is mainly to get        around the problem when some registration owner cannot be        reached in order to make necessary updates.4.  What To Put In Documents   The previous sections presented some issues that should be considered   in formulating a policy for assigning well-known numbers and other   protocol constants. It is the Working Group and/or document author's   job to formulate an appropriate policy and specify it in the   appropriate document. In some cases, having an "IANA Considerations"   section may be appropriate. Specifically, documents that create an   name space (or modify the definition of an existing space) and that   expect the IANA to play a role in maintaining that space (e.g.,   serving as a repository for registered values) MUST document the   process through which future assignments are made.  Such a section   MUST state clearly:      - whether or not an application for an assigned number needs to be        reviewed. If review is necessary, the review mechanism MUST be        specified.  When a Designated Expert is used, documents MUST NOT        name the Designated Expert in the document itself; instead, the        name should be relayed to the appropriate IESG Area Director at        the time the document is sent to the IESG for approval.      - If the request should also be reviewed on a specific public        mailing list (such as the ietf-types@iana.org for media types),        that mailing address should be specified. Note, however, that        use of a Designated Expert MUST also be specified.      - if the IANA is expected to make assignments without requiring an        outside review, sufficient guidance MUST be provided so that the        requests can be evaluated with minimal subjectivity.   Authors SHOULD attempt to provide guidelines that allow the IANA to   assign new values directly without requiring review by a Designated   Expert. This can be done easily in many cases by designating a range   of values for direct assignment by the IANA while simultaneously   reserving a sufficient portion of the name space for future use by   requiring that assignments from that space be made only after a more   stringent review.   Finally, it is quite acceptable to pick one of the example policies   cited above and refer to it by name.  For example, a document could   say something like:Narten & Alvestrand      Best Current Practice                  [Page 7]

RFC 2434           Guidelines for IANA Considerations       October 1998        Following the policies outlined in [IANA-CONSIDERATIONS],        numbers in the range 0-63 are allocated as First Come First        Served, numbers between 64-240 are allocated through an IETF        Consensus action and values in the range 241-255 are reserved        for Private Use.   For examples of documents that provide good and detailed guidance to   the IANA on the issue of assigning numbers, consult [MIME-REG, MIME-   LANG].5.  Applicability to Past and Future RFCs   For all existing RFCs that either explicitly or implicitly rely on   the IANA to evaluate assignments without specifying a precise   evaluation policy, the IANA will continue to decide what policy is   appropriate. The default policy has been first come, first served.   Changes to existing policies can always be initiated through the   normal IETF consensus process.   All future RFCs that either explicitly or implicitly rely on the IANA   to register or otherwise manage assignments MUST provide guidelines   for managing the name space.6.  Security Considerations   Information that creates or updates a registration needs to be   authenticated.   Information concerning possible security vulnerabilities of a   protocol may change over time. Likewise, security vulnerabilities   related to how an assigned number is used (e.g., if it identifies a   protocol) may change as well. As new vulnerabilities are discovered,   information about such vulnerabilities may need to be attached to   existing registrations, so that users are not mislead as to the true   security issues surrounding the use of a registered number.   An analysis of security issues is required for all parameters (data   types, operation codes, keywords, etc.) used in IETF protocols or   registered by the IANA. All descriptions of security issues must be   as accurate as possible regardless of level of registration.  In   particular, a statement that there are "no security issues associated   with this type" must not given when it would be more accurate to   state that "the security issues associated with this type have not   been assessed".Narten & Alvestrand      Best Current Practice                  [Page 8]

RFC 2434           Guidelines for IANA Considerations       October 19987.  Acknowledgments   Jon Postel and Joyce K. Reynolds provided a detailed explanation on   what the IANA needs in order to manage assignments efficiently, and   patiently provided comments on multiple versions of this document.   Brian Carpenter provided helpful comments on earlier versions of the   document. One paragraph in the Security Considerations section was   borrowed from [MIME-REG].8.  References   [ASSIGNED]            Reynolds, J., and J. Postel, "Assigned                         Numbers", STD 2,RFC 1700, October 1994.  See                         also:http://www.iana.org/numbers.html   [BGP4-EXT]            Bates. T., Chandra, R., Katz, D. and Y.                         Rekhter, "Multiprotocol Extensions for BGP-4",RFC 2283, February 1998.   [DHCP-OPTIONS]        Alexander, S. and R. Droms, "DHCP Options and                         BOOTP Vendor Extensions",RFC 2132, March 1997.   [IANA-CONSIDERATIONS] Alvestrand, H. and T. Narten, "Guidelines for                         Writing an IANA Considerations Section in                         RFCs",BCP 26,RFC 2434, October 1998.   [IETF-PROCESS]        Bradner, S., "The Internet Standards Process --                         Revision 3",BCP 9,RFC 2026, October 1996.   [IP]                  Postel, J., "Internet Protocol", STD 5,RFC791, September 1981.   [IPSEC]               Atkinson, R., "Security Architecture for the                         Internet Protocol",RFC 1825, August 1995.   [KEYWORDS]            Bradner, S., "Key words for use in RFCs to                         Indicate Requirement Levels",BCP 14,RFC 2119,                         March 1997.   [MIME-LANG]           Freed, N. and K. Moore, "MIME Parameter Value                         and Encoded Word Extensions: Character Sets,                         Languages, and Continuations",RFC 2184, August                         1997.   [MIME-REG]            Freed, N., Klensin, J. and J. Postel,                         "Multipurpose Internet Mail Extension (MIME)                         Part Four: Registration Procedures",RFC 2048,                         November 1996.Narten & Alvestrand      Best Current Practice                  [Page 9]

RFC 2434           Guidelines for IANA Considerations       October 1998   [SCSP]                Luciani, J., Armitage, G. and J. Halpern,                         "Server Cache Synchronization Protocol (SCSP)",RFC 2334, April 1998.   [SMTP-EXT]            Klensin, J., Freed, N., Rose, M., Stefferud, E.                         and D. Crocker, "SMTP Service Extensions",RFC1869, November 1995.9.  Authors' Addresses   Thomas Narten   IBM Corporation   3039 Cornwallis Ave.   PO Box 12195 - BRQA/502   Research Triangle Park, NC 27709-2195   Phone: 919-254-7798   EMail: narten@raleigh.ibm.com   Harald Tveit Alvestrand   Maxware   Pirsenteret   N-7005 Trondheim   Norway   Phone: +47 73 54 57 97   EMail: Harald@Alvestrand.noNarten & Alvestrand      Best Current Practice                 [Page 10]

RFC 2434           Guidelines for IANA Considerations       October 199810.  Full Copyright Statement   Copyright (C) The Internet Society (1998).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS 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.Narten & Alvestrand      Best Current Practice                 [Page 11]