INTERNET-DRAFT                                             Thomas Narten
<draft-iesg-iana-considerations-02.txt>          Harald Tveit Alvestrand
                                                        January 30, 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,
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   This Internet Draft expires July 30, 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.  Registration maintenance.................................    6

   4.  What To Put In Documents.................................    7

   5.  Security Considerations..................................    8

   6.  Acknowledgements.........................................    8

   7.  References...............................................    8

   8.  Authors' Addresses.......................................    9

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
   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

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

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
   subject 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
             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 higher
             levels of the namespace according to one of the other

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             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 must be
             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]

   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 for media types) or on a more general
   mailing list on which (e.g., that of a current or former IETF Working
   Group).  Such a mailing list may serve to give new registrations a
   public review before getting registered, or give advice for persons
   who want help in understanding what a proper registration should

   Since the IANA cannot participate in all of these mailing lists and

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   cannot determine if or when such discussion reaches a consensus, the
   IANA in all cases relies on a designated subject matter expert to
   advise it in these matters.  That is, the IANA must be directed to
   forward the requests it receives to a specific point-of-contact (one
   or a small number of individuals) 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. In those cases where wide
   review of a request is needed, it is the responsibility of the
   designated subject matter 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

   In some cases, it makes 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
   two parts. Option numbers in the range of 1-127 are globally unique
   and assigned according to the Specification Required policy described
   earlier, while options number 128-254 are "site specific", i.e.,
   Local Use.

3.  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.

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4.  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 must be provided.

      - who has authority to replace the designated subject matter
        expert, should a replacement be needed (e.g., if multiple
        attempts to reach the designated subject matter fail). The
        specific procedure to appoint the person should also be
        indicated; it may often be appropriate to let the relevant IESG
        Area Director designate the subject matter expert when a
        replacement is necessary.

      - If the request should also be reviewed by a specific public
        mailing list (such as the 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.

   It should also be noted that the following are unacceptable:

      - listing a Working Group mailing list as the designated subject
        matter expert

      - specifying that "the current Working Group Chairs of the FooBar
        Working Group" are the designated subject matter experts, since
        Working Groups eventually close down. However, it is acceptable
        to list the current WG Chairs individually.

   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

   For examples of documents that provide good and detailed guidance to

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   the IANA on the issue of assigning identifiers, consult [MIME-REG,

5.  Security Considerations

   Information that creates or updates a registration needs to be

   Information concerning possible security vulnerabilities of a
   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 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.

6.  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].

7.  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

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     [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-

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

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

     [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

8.  Authors' Addresses

   Thomas Narten
   IBM Corporation
   3039 Cornwallis Ave.
   PO Box 12195 - BRQA/502
   Research Triangle Park, NC 27709-2195

   Phone: 919-254-7798

   Harald Tveit Alvestrand
   P.O.Box 6883 Elgeseter

   Phone: +47 73 59 70 94

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