INTERNET-DRAFT Thomas Narten IBM Harald Tveit Alvestrand UNINETT October 6, 1997 Guidelines for Writing an IANA Considerations Section in RFCs Status of this Memo This document is an Internet-Draft. 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." To learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ds.internic.net (US East Coast), nic.nordu.net (Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim). Distribution of this memo is unlimited. This Internet Draft expires April 6, 1998. 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., a new option type in DHCP). To insure that such quantities have unique values, their assignment must be administered by a central authority. In the Internet, that role is provided by the Internet Assigned Numbers Authority (IANA). In order for the IANA to manage a given numbering 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 numbering space, the IANA must be given clear and concise draft-iesg-iana-considerations-00.txt [Page 1] INTERNET-DRAFT October 6, 1997 guidelines describing that role. This document discusses issues that should be considered in formulating an identifier assignment policy and provides guidelines to document authors on the specific text that must be included in documents that place demands on the IANA. draft-iesg-iana-considerations-00.txt [Page 2] INTERNET-DRAFT October 6, 1997 Contents Status of this Memo.......................................... 1 1. Introduction............................................. 3 2. Issues To Consider....................................... 4 3. What To Put In Documents................................. 6 4. Security Considerations.................................. 6 5. References............................................... 6 6. Authors' Addresses....................................... 7 1. 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]). 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]). To insure that such fields have unique values, their assignment must be administered by a central authority. In the Internet, that role is provided by the Internet Assigned Numbers Authority (IANA). In order for the IANA to manage a given numbering 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 identifiers. 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 [XXX reference]. When a name space can be delegated, the IANA only deals with assignments at the top level. draft-iesg-iana-considerations-00.txt [Page 3] INTERNET-DRAFT October 6, 1997 2. Issues To Consider The primary issue to consider in managing a numbering 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. On the other hand, it may be perfectly reasonable to hand out new values to anyone that wants one, if the space is essentially unlimited. Even when the space is essentially unlimited, however, it may be desirable to have a minimal review to prevent hoarding of the 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 most cases, some review of prospective allocations is appropriate, and the first question to answer is who should perform the review. In some cases, it is reasonable for the IANA to review prospective assignments. In such cases, the IANA will need specific guidelines on what types of requests it should grant, and what information must be provided before a request of an assigned number will be considered. Note that the IANA will not define such a policy; it should be given a set of guidelines that allow it to make allocation decisions with little subjectivity. The following are example policies, some of which are in use today: Free For All - For 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. Hierarchical allocation - Delegated managers can assign identifiers provided they have been given control over that part of the identifier space. IANA controls the top levels of the namespace according to one of the other policies. Examples: DNS names First Come First Served - Anyone can obtain an identifier, so long as they provide a point of contact and a brief description of what the identifier would be used for. For numbers, the draft-iesg-iana-considerations-00.txt [Page 4] INTERNET-DRAFT October 6, 1997 exact value is generally assigned by the IANA, with names, specific names are usually requested. Examples: MIME types, TCP and UDP port numbers. Documentation Required - Values and their meaning must be documented in an RFC or other permanent reference, in sufficient detail so that interoperability between independent implementations is possible. Examples: XXX IESG Action - IESG must explicitly approve new values. Examples: XXX Standards Action - Only identifiers that have been documented in standards track RFCs approved by the IESG will be registered. Examples: XXX In some cases, it may be appropriate for the IANA to serve as a point-of-contact for publishing information about numbers that have been assigned, without actually having it evaluate and grant requests. For example, it is 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 mailing list associated with an IETF Working Group. Since the IANA cannot participate in all of these mailing lists and cannot determine if or when such discussion reaches a consensus, the IANA will rely on a designated subject matter expert to advise it in these matters. Consequently, the IANA should be directed to forward the requests it receives to a specific point-of-contact or mailing list (i.e., a mailing list set up specifically for the purpose of discussing such requests) and act upon the returned recommendation from the designated subject matter expert. In all cases, it is the designated subject matter expert that the IANA relies on for an authoritative response. Of course, combinations of the above are also possible. When defining new DHCP option types [DHCP], for example, the IANA assigns options to anyone, with the stipulation that the number will be returned to the IANA should the option fail to gain acceptance. In some cases, it may make sense to partition the number space into several categories, with assignments out of each category handled differently. For example, the DHCP option space [DHCP] is split into draft-iesg-iana-considerations-00.txt [Page 5] INTERNET-DRAFT October 6, 1997 two parts. Option numbers in the range of 1-127 are globally unique and assigned according to the Documentation Required policy described earlier, while options number 128-254 are "site specific", i.e., Free For All. 3. What To Put In Documents The previous section 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. Such a section should state clearly: - who reviews an application for an assigned number. If a request should be reviewed by a designated subject matter expert, contact information for that person should be provided. If the request should also be reviewed by a specific mailing list (such as the ietf-types@iana.org for media types), that mailing address should be specified. - if the IANA is expected to review requests itself, sufficient guidance must be provided so that the requests can be evaluated with minimal subjectivity. 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: numbers are allocated as First Come First Served as defined in [RFC ASSIGN] XXX: give pointers to 3 or 4 particularly good examples in existing RFCs? 1) DHCP options seems reasonable. Others? 4. Security Considerations There are no known security issues raised by this document. 5. References [DHCP-OPTIONS] S. Alexander, R. Droms, DHCP Options and BOOTP Vendor Extensions, RFC 2132, March 1997. [IP] J. Postel, Internet Protocol, RFC 791, September 1, 1981. draft-iesg-iana-considerations-00.txt [Page 6] INTERNET-DRAFT October 6, 1997 [MIME] N. Freed, J. Klensin & J. Postel, Multipurpose Internet Mail Extension (MIME) Part Four: Registration Procedures. RFC 2048, November, 1996. 6. 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 UNINETT P.O.Box 6883 Elgeseter N-7002 TRONDHEIM NORWAY Phone: +47 73 59 70 94 EMail: Harald.T.Alvestrand@uninett.no draft-iesg-iana-considerations-00.txt [Page 7]