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rfc:rfc2434

Network Working Group T. Narten Request for Comments: 2434 IBM BCP: 26 H. Alvestrand Category: Best Current Practice Maxware

                                                          October 1998
   Guidelines for Writing an IANA Considerations Section in RFCs

Status 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 1998

Table of Contents

 Status of this Memo..........................................    1
 1.  Introduction.............................................    2
 2.  Issues To Consider.......................................    3
 3.  Registration maintenance.................................    6
 4.  What To Put In Documents.................................    7
 5.  Applicability to Past and Future RFCs....................    8
 6.  Security Considerations..................................    8
 7.  Acknowledgments..........................................    9
 8.  References...............................................    9
 9.  Authors' Addresses.......................................   10
 10. Full Copyright Statement.................................   11

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-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 space

Narten & 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 in RFC 2119 [KEYWORDS]. In this case,
 "the specification" as used by RFC 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 the

Narten & 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 in Section 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:
  1. Let the author update the registration, subject to the same

constraints and review as with new registrations.

  1. 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

  1. 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:
  1. 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.
  1. 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.
  1. 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 1998

7. 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, RFC
                       791, 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", RFC
                       1869, 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.no

Narten & Alvestrand Best Current Practice [Page 10] RFC 2434 Guidelines for IANA Considerations October 1998

10. 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]

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