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Versions: 00 01 02 03 04 05 rfc2434                                     
INTERNET-DRAFT                                             Thomas Narten
<draft-iesg-iana-considerations-03.txt>          Harald Tveit Alvestrand
                                                          March 13, 1998

       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
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   material or to cite them other than as "work in progress."

   To learn the current status of any Internet-Draft, please check the
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   Distribution of this memo is unlimited.

   This Internet Draft expires September 13, 1998.


   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 authentication algorithm).  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

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   instructions 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

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   Status of this Memo..........................................    1

   1.  Introduction.............................................    3

   2.  Issues To Consider.......................................    4

   3.  Designated Experts.......................................    6

   4.  Registration maintenance.................................    7

   5.  What To Put In Documents.................................    7

   6.  Applicability to Past and Future RFCs....................    8

   7.  Security Considerations..................................    8

   8.  Acknowledgements.........................................    9

   9.  References...............................................    9

   10.  Authors' Addresses......................................   10

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
   authentication algorithm for IPSec [IPSEC]).  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

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   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
   can be delegated, the IANA only deals with assignments at the top

   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 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. 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 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

   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 consider is who should perform the review.
   In some cases, reviewing requests is straightforward and requires no
   subjective decision making. On those cases, it is reasonable for the
   IANA to review prospective assignments, provided that the IANA is
   given 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 an
   assignment 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:

      Local Use - 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

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             such assignments and assignments are not generally useful
             for interoperability.

             Examples: Site-specific options in DHCP [DHCP] have
             significance only within a single site. XXX X-foo header
             lines in email message (and mime types?)

      Hierarchical allocation - Delegated managers can assign
             identifiers provided they have been given control over that
             part of the identifier space.  IANA controls the higher
             levels of the namespace according to one of the other

             Examples: DNS names, Object Identifiers

      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
             exact value is generally assigned by the IANA, with names,
             specific names are usually requested.

             Examples: vnd. MIME types [MIME-REG], TCP and UDP port

      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

             Examples: SCSP [SCSP]

      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 - Identifiers 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 number

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   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 number 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
   via a more stringent review process.

3.  Designated Experts

   In many cases, it is 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 may be 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 Working Group).
   Such a mailing list provides a way for new registrations to be
   publically reviewed prior to getting assigned, or to give advice for
   persons who want help in understanding what a proper registration
   should contain.

   Since the IANA cannot participate in all of these mailing lists and
   cannot determine if or when such discussion reaches a consensus, the
   IANA in all cases relies 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. In all cases, it is the designated expert that the
   IANA relies on for an authoritative response. In those cases where
   wide review of a request is needed, it is the responsibility of the
   designated expert to initiate such a review (e.g., by engaging the
   relevant mailing lists). In no cases will the IANA allow general
   mailing lists (e.g., that of a former or existing IETF Working Group)
   to fill the role of the designated subject matter expert.

   Designated experts serve at the pleasure of the IESG (e.g,, they are
   appointed by the relevant Area Director) and are typically named at
   the time a document that creates a new numbering space is published
   as an RFC.  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].

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4.  Registration maintenance

   Registrations sometimes contain information that needs to be
   maintained; in particular, point of contact information may need to
   be changed, claims of freedom from security problems may need to be
   modified, or new versions of a registration may need to be published.

   A document must clearly state who is responsible for such
   maintenance. 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

      - 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.

   In the absense of specific instructions, the designated expert will
   assume such responsibilities.

5.  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
   identifier 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
   should state clearly:

      - whether or not an application for an assigned number should
        first be reviewed by a designated expert. 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.

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      - If the request should also be reviewed by a specific public
        mailing list (such as the ietf-types@iana.org for media types),
        that mailing address should be specified. Note, however, that a
        designated subject matter expert must also 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.

   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 some of the identifier space for future use by requiring
   that assignments from that space be made only after a more stringent

   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 in the range 0-127 are allocated as First Come First
        Served as defined in [IANA-CONSIDERATIONS], numbers between
        128-255 must be approved by the designated expert.

   For examples of documents that provide good and detailed guidance to
   the IANA on the issue of assigning identifiers, consult [MIME-REG,

6.  Applicability to Past and Future RFCs

   All existing RFCs that either explicitely or implicitly rely on the
   IANA to evaluate assignments without specifying a precise evaluation
   policy, will have assignments evaluated by a designated expert, as
   outlined in Section 3.

   All future RFCs that either explicitely or implicitly rely on the
   IANA to register or otherwise manage assignments MUST provide
   guidelines for managing the identifier space.

7.  Security Considerations

   Information that creates or updates a registration needs to be

   Information concerning possible security vulnerabilities of a

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   protocol may change over time. Consequently, claims as to the
   security properties of a registered 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 properties of a
   registered protocol.

   An analysis of security issues is required for all types registered
   in the IETF Tree [MIME-REG].  A similar analysis for media types
   registered in the vendor or personal trees is encouraged but not
   required.  However, regardless of what security analysis has or has
   not been done, all descriptions of security issues must be as
   accurate as possible regardless of registration tree.  In particular,
   a statement that there are "no security issues associated with this
   type" must not be confused with "the security issues associated with
   this type have not been assessed".

   Delegations of a name space should only be assigned to someone with
   adequate security.

8.  Acknowledgements

   Jon Postel and Joyce Reynolds provided a detailed explanation on what
   the IANA needs in order to manage assignments efficiently. Brian
   Carpenter provided helpful comments on earlier versions of the
   document. One paragraph in the Security Considerations section was
   borrowed from [MIME-REG].

9.  References

     [ASSIGNED] Reynolds, J., Postel, J., "Assigned Numbers", October
             1994k, RFC 1700.

     [BGP4-EXT] Bates. T., Chandra, R., Katz, D., Rekhter, Y.,
             Multiprotocol Extensions for BGP-4, draft-ietf-idr-bgp4-
             multiprotocol-02.txt, January, 1998

     [DHCP-OPTIONS] S. Alexander, R. Droms, DHCP Options and BOOTP
             Vendor Extensions, RFC 2132, March 1997.

     [IANA-CONSIDERATIONS] Alvestrand, H., Narten, T., "Guidelines for
             Writing an IANA Considerations Section in RFCs", draft-

     [IETF-PROCESS] Bradner, S., "The Internet Standards Process --
             Revision 3", RFC 2026, October 1996.

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     [IP] J. Postel, Internet Protocol, RFC 791, September 1, 1981.

     [IPSEC] Atkinson, R., Security Architecture for the Internet
             Protocol, RFC 1825, August 1995.

     [KEYWORDS] S. Bradner, "Key words for use in RFCs to Indicate
             Requirement Levels", RFC 2119, March 1997.

     [MIME-LANG] Freed, N., Moore, K., "MIME Parameter Value and Encoded
             Word Extensions: Character Sets, Languages, and
             Continuations", RFC 2184, August, 1997.

     [MIME-REG] N. Freed, J. Klensin & J. Postel, Multipurpose Internet
             Mail Extension (MIME) Part Four: Registration Procedures.
             RFC 2048, November, 1996.

     [SCSP] Luciani, J., Armitage, G, Halpern, J., "Server Cache
             Synchronization Protocol (SCSP)" draft-ietf-ion-scsp-

     [SMTP-EXT] Klensin, J., Freed, N., Rose, M., Stefferud, E.,
             Crocker, D.. "SMTP Service Extensions", RFC 1869, November

10.  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
   N-7005 Trondheim

   Phone: +47 73 54 57 97
   Email: Harald@Alvestrand.no

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