Internet DRAFT - draft-narten-iana-considerations-rfc2434bis


INTERNET-DRAFT                                             Thomas Narten
<draft-narten-iana-considerations-rfc2434bis-09.txt>   Harald Alvestrand
Obsoletes (if approved): 2434                                     Google
Expires: September 21, 2007                               March 26, 2008
Intended Status: BCP

       Guidelines for Writing an IANA Considerations Section in RFCs


Status of this Memo

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   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
   transform for IPsec).  To ensure that such quantities have consistent
   values and interpretations across all implementations, their
   assignment must be administered by a central authority. For IETF
   protocols, that role is provided by the Internet Assigned Numbers

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   Authority (IANA).

   In order for IANA to manage a given name space prudently, it needs
   guidelines describing the conditions under which new values can be
   assigned, or when modifications to existing values can be made. If
   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 IANA.

   This document obsoletes RFC 2434.

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

   1.  Introduction.............................................    4

   2.  Why Management of a Name Space May be Necessary..........    5

   3.  Designated Experts.......................................    5
      3.1.  The Motivation For Designated Experts...............    5
      3.2.  The Role of the Designated Expert...................    7
      3.3.  Designated Expert Reviews...........................    8

   4.  Creating A Registry......................................    9
      4.1.  Well-Known IANA Policy Definitions..................   10
      4.2.  What To Put In Documents That Create A Registry.....   13
      4.3.  Updating IANA Guidelines For Existing Registries....   16

   5.  Registering New Values In An Existing Registry...........   16
      5.1.  What to Put In Documents When Registering Values....   16
      5.2.  Updating Registrations..............................   18
      5.3.  Overriding Registration Procedures..................   18

   6.  Miscellaneous Issues.....................................   19
      6.1.  When There Are No IANA Actions......................   19
      6.2.  Namespaces Lacking Documented Guidance..............   20
      6.3.  After-The-Fact Registrations........................   20
      6.4.  Reclaiming Assigned Values..........................   20

   7.  Appeals..................................................   21

   8.  Mailing Lists............................................   21

   9.  Security Considerations..................................   21

   10.  Changes Relative to RFC 2434............................   22

   11.  IANA Considerations.....................................   23

   12.  Acknowledgments.........................................   23

   13.  Normative References....................................   23

   14.  Informative References..................................   23

   15.  Authors' Addresses......................................   26

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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 media types [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-OPTIONS] or a new encryption or
   authentication transform for IPsec [IPSEC]).  To ensure 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) [IANA-MOU].

   In this document, we call the set of possible values for such a field
   a "name space"; its actual value may be a text string, a number or
   another kind of value. The binding or association of a specific value
   with a particular purpose within a name space is called an assigned
   number (or assigned value, or sometimes a "code point", "protocol
   constant", or "protocol parameter"). Each assignment of a value in a
   name space is called a registration.

   In order for IANA to manage a given name space prudently, it needs
   guidelines describing the conditions under which new values should be
   assigned, or when (and how) modifications to existing values can be
   made. This document provides guidelines to authors on what sort of
   text should be added to their documents in order to provide IANA
   clear guidelines and reviews issues that should be considered in
   formulating an appropriate policy for assigning numbers to name

   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]; IANA manages the
   subtree rooted at "" ( .  When a name
   space is delegated, the scope of IANA is limited to the parts of the
   namespace where IANA has authority.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [KEYWORDS].
   For this document, "the specification" as used by RFC 2119 refers to
   the processing of protocol documents within the IETF standards

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2.  Why Management of a Name Space May be Necessary

   One 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 prevent exhaustion of the space. If the space is
   essentially unlimited, on the other hand, potential exhaustion will
   probably not be a practical concern at all.  Even when the space is
   essentially unlimited, however, it is usually desirable to have at
   least a minimal review prior to assignment in order to:

    - prevent the hoarding of or unnecessary wasting of values. For
      example, if the space consists of text strings, it may be
      desirable to prevent entities from obtaining large sets of strings
      that correspond to desirable names (e.g., existing company names).

    - provide a sanity check that the request actually makes sense and
      is necessary. Experience has shown that some level of minimal
      review from a subject matter expert is useful to prevent
      assignments in cases where the request is malformed or not
      actually needed (i.e., an existing assignment for an essentially
      equivalent service already exists).

   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 IANA for dealing with assignments.

   A third, and perhaps most important consideration, concerns potential
   impact on interoperability of unreviewed extensions. Proposed
   protocol extensions generally benefit from community review; indeed,
   review is often essential to avoid future interoperability problems

   When the name space is essentially unlimited and there are no
   potential interoperability issues, assigned numbers can safely be
   given out to anyone without any subjective review. In such cases,
   IANA can make assignments directly, provided that IANA is given
   specific instructions on what types of requests it should grant, and
   what information must be provided as part of a well-formed request
   for an assigned number.

3.  Designated Experts

3.1.  The Motivation For Designated Experts

   It should be noted that IANA does not create or define assignment
   policy itself; rather, it carries out policies that have been defined

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   by others and published in RFCs.  IANA must be given a set of
   guidelines that allow it to make allocation decisions with minimal
   subjectivity and without requiring any technical expertise with
   respect to the protocols that make use of a registry.

   In many cases, some review of prospective allocations is appropriate,
   and the question becomes who should perform the review and what is
   the purpose of the review.  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 ensure community review of prospective assignments is to
   have the requester submit a document for publication as an RFC. Such
   an action helps ensure that the specification is publicly and
   permanently available, and allows some review of the specification
   prior to publication and assignment of the requested code points.
   This is the preferred way of ensuring review, and is particularly
   important if any potential interoperability issues can arise. For
   example, some 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 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 to persons wanting help in understanding what a
   proper registration should contain.

   While discussion on a mailing list can provide valuable technical
   feedback, opinions may vary and discussions may continue for some
   time without clear resolution.  In addition, IANA cannot participate
   in all of these mailing lists and cannot determine if or when such
   discussions reach consensus.  Therefore, IANA relies on a "designated
   expert" for advice regarding the specific question of whether an
   assignment should be made. The designated expert is an individual who
   is responsible for carrying out an appropriate evaluation and
   returning a recommendation to IANA.

   It should be noted that a key motivation for having designated

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   experts is for the IETF to provide IANA with a subject matter expert
   to whom the evaluation process can be delegated. IANA forwards
   requests for an assignment to the expert for evaluation, and the
   expert (after performing the evaluation) informs IANA whether or not
   to make the assignment or registration.

3.2.  The Role of the Designated Expert

   The designated expert is responsible for initiating and coordinating
   the appropriate review of an assignment request.  The review may be
   wide or narrow, depending to the situation and the judgment of the
   designated expert.  This may involve consultation with a set of
   technology experts, discussion on a public mailing list, or
   consultation with a working group (or its mailing list if the working
   group has disbanded), etc. Ideally, the designated expert follows
   specific review criteria as documented with the protocol that creates
   or uses the namespace. (See the IANA Considerations sections of
   [RFC3748,RFC3575] for examples that have been done for specific name

   Designated experts are expected to be able to defend their decisions
   to the IETF community and the evaluation process is not intended to
   be secretive or bestow unquestioned power on the expert. Experts are
   expected to apply applicable documented review or vetting procedures,
   or in the absence of documented criteria, follow generally-accepted
   norms, e.g., those in section 3.3.

   Section 5.2 discusses disputes and appeals in more detail.

   Designated experts are appointed by the IESG (normally upon
   recommendation by the relevant Area Director). They are typically
   named at the time a document creating or updating a name space is
   approved by the IESG, but as experts originally appointed may later
   become unavailable, the IESG will appoint replacements if necessary.

   For some registries, it has proven useful to have multiple designated
   experts. Sometimes those experts work together in evaluating a
   request, while in other cases additional experts serve as backups. In
   cases of disagreement among those experts, it is the responsibility
   of those experts to make a single clear recommendation to IANA. It is
   not appropriate for IANA to resolve disputes among experts. In
   extreme situations (e.g., deadlock) the IESG may need to step in to
   resolve the problem.

   In registries where a pool of experts evaluates requests, the pool
   should have a single chair responsible for defining how requests are
   to be assigned to and reviewed by experts. In some cases, the expert

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   pool may consist of a primary and backups, with the backups involved
   only when the primary expert is unavailable. In other cases, IANA
   might assign requests to a individual members in sequential or
   approximate random order. In the event that IANA finds itself havnig
   received conflicting advice from its experts, it is the
   responsibility of the pool's chair to resolve the issue and provide
   IANA with clear

   Since the designated experts are appointed by the IESG, they may be
   removed by the IESG.

3.3.  Designated Expert Reviews

   In the eight years since RFC 2434 was published and has been put to
   use, experience has led to the following observations:

    - a designated expert must respond in a timely fashion, normally
      within a week for simple requests to a few weeks for more complex
      ones. Unreasonable delays can cause significant problems for those
      needing assignments, such as when products need code points to
      ship. This is not to say that all reviews can be completed under a
      firm deadline, but they must be started, and the requester and
      IANA should have some transparency into the process if an answer
      cannot be given quickly.

    - if a designated expert does not respond to IANA's requests within
      a reasonable period of time, either with a response, or with a
      reasonable explanation for a delay (e.g., some requests may be
      particularly complex), and if this is a recurring event, IANA must
      raise the issue with the IESG.  Because of the problems caused by
      delayed evaluations and assignments, the IESG should take
      appropriate actions to ensure that the expert understands and
      accepts their responsibilities, or appoint a new expert.

    - The designated expert is not required to personally bear the
      burden of evaluating and deciding all requests, but acts as a
      shepherd for the request, enlisting the help of others as
      appropriate. In the case that a request is denied, and rejecting
      the request is likely to be controversial, the expert should have
      the support of other subject matter experts. That is, the expert
      must be able to defend a decision to the community as a whole.

   In the case where a designated expert is used, but there are no
   specific documented criteria for performing an evaluation, the
   presumption should be that a code point should be granted, unless
   there is a compelling reason to the contrary. Possible reasons to
   deny a request include:

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    - scarcity of codepoints, where the finite remaining codepoints
      should be prudently managed, or when a request for a large number
      of codepoints is made, when a single codepoint is the norm.

    - documentation is not of sufficient clarity to evaluate or ensure

    - the code point is needed for a protocol extension, but the
      extension is not consistent with the documented (or generally
      understood) architecture of the base protocol being extended, and
      would be harmful to the protocol if widely deployed. It is not the
      intent that "inconsistencies" refer to minor differences "of a
      personal preference nature;" instead, they refer to significant
      differences such as inconsistencies with the underlying security
      model, implying a change to the semantics of an existing message
      type or operation, requiring unwarranted changes in deployed
      systems (compared with alternate ways of achieving a similar
      result), etc.

    - the extension would cause problems with existing deployed systems.

    - the extension would conflict with one under active development by
      the IETF, and having both would harm rather than foster

4.  Creating A Registry

   Creating a registry involves describing the name spaces to be
   created, an initial set of assignments (if appropriate) and
   guidelines on how future assignments are to be made.

   Once a registry has been created, IANA records assignments that have
   been made. The following labels describe the status of an individual
   (or range) of assignments:

     Private Use: Private use only (not assigned), as described in
        Section 4.1

     Experimental: Available for experimental use as described in
        [EXPERIMENTATION]. IANA does not record specific assignments for
        any particular use.

     Unassigned: Unused and available for assignment via documented

     Reserved:  Not to be assigned. Reserved values are held for special
        uses, such as to extend the name space when it become exhausted.

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        Reserved values are not available for general assignment.

4.1.  Well-Known IANA Policy Definitions

   The following are some defined policies, some of which are in use
   today. These cover a range of typical policies that have been used to
   date to describe the procedure for assigning new values in a name
   space. It is not required that documents use these terms; the actual
   requirement is that the instructions to IANA are clear and
   unambiguous. However, use of these terms is RECOMMENDED where
   possible, since their meaning is widely understood.

      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 (since IANA does not record
             them) and assignments are not generally useful for broad
             interoperability. It is the responsibility of the sites
             making use of the Private Use range to ensure that no
             conflicts occur (within the intended scope of use).

             Examples: Site-specific options in DHCP [DHCP-IANA], Fibre
             Channel Port Type Registry [RFC4044], Exchange Types in the
             IKEv2 header [RFC4306].

      Experimental Use - Similar to private or local use only, with the
             purpose being to facilitate experimentation. See
             [EXPERIMENTATION] for details.

             Example: Experimental Values in IPv4, IPv6, ICMPv4, ICMPv6,
             UDP, and TCP Headers [RFC4727].

      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, IP addresses.

      First Come First Served - Assignments are made to anyone on a
             first come, first served basis. There is no substantive
             review of the request, other than to ensure that it is
             well-formed and doesn't duplicate an existing assignment.
             However, requests must include a minimal amount of clerical
             information, such as a a point of contact (including an
             email address) and a brief description of how the value

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             will be used. Additional information specific to the type
             of value requested may also need to be provided, as defined
             by the name space. For numbers, the exact value is
             generally assigned by IANA; with names, specific text
             strings can usually be requested.

             Examples: SASL mechanism names [RFC4422], LDAP Protocol
             Mechanisms and LDAP Syntax [RFC4520].

      Expert Review (or Designated Expert) - approval by a Designated
             Expert is required. The required documentation and review
             criteria for use by the Designated Expert should be
             provided when defining the registry. For example, see
             Sections 6 and 7.2 in [RFC3748].

             Examples: EAP Method Types [RFC3748], HTTP Digest AKA
             algorithm versions [RFC4169], URI schemes [RFC4395],
             GEOPRIV Location Types [RFC4589].

      Specification Required - Values and their meaning must be
             documented in a permanent and readily available public
             specification, in sufficient detail so that
             interoperability between independent implementations is
             possible. When used, Specification Required also implies
             usage of a Designated Expert, who will review the public
             specification and evaluate whether it is sufficiently clear
             to allow interoperable implementations. The intention
             behind "permanent and readily available" is that a document
             can reasonably be expected to be findable and retrievable
             long after IANA assignment of the requested value.
             Publication of an RFC is an ideal means of achieving this
             requirement, but Specification Required is intended to also
             cover the case of a document published outside of the RFC
             path. For RFC publication, the normal RFC review process is
             expected to provide the necessary review for
             interoperability, though the Designated Expert may be a
             particularly well-qualified person to perform such a

             Examples: Diffserv-aware TE Bandwidth Constraints Model
             Identifiers [RFC4124], TLS ClientCertificateType
             identifiers [RFC4346], ROHC Profile Identifiers [RFC4995].

      RFC Required - RFC publication (either as IETF Submission or as an
             RFC Editor submission [RFC3932]) suffices. Unless otherwise
             specified, any type of RFC is sufficient (e.g.,
             Informational, Experimental, Standards Track, etc.)

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      IETF Review - (Formerly called "IETF Consensus" in [IANA-
             CONSIDERATIONS]) New values are assigned only through RFCs
             that have been shepherded through the IESG as AD-Sponsored
             or IETF WGs Documents [RFC3932,RFC3978]. The intention is
             that the document and proposed assignment will be reviewed
             by the IESG and appropriate IETF WGs (or experts, if
             suitable working groups no longer exist) to ensure that the
             proposed assignment will not negatively impact
             interoperability or otherwise extend IETF protocols in an
             inappropriate or damaging manner.

             To ensure adequate community review, such documents are
             shepherded through the IESG as AD-sponsored (or WG)
             documents with an IETF Last Call.

             Examples: IPSECKEY Algorithm Types [RFC4025], Accounting-
             Auth-Method AVP values in DIAMETER [RFC4005], TLS Handshake
             Hello Extensions [RFC4366].

      Standards Action - Values are assigned only for Standards Track
             RFCs approved by the IESG.

             Examples: BGP message types [RFC4271], Mobile Node
             Identifier option types [RFC4283], DCCP Packet Types

      IESG Approval - New assignments may be approved by the IESG.
             Although there is no requirement that the request be
             documented in an RFC, the IESG has discretion to request
             documents or other supporting materials on a case-by-case

             IESG Approval is not intended to be used often or as a
             "common case;" indeed, it has seldom been used in practice
             during the period RFC 2434 was in effect. Rather, it is
             intended to be available in conjunction with other policies
             as a fall-back mechanism in the case where one of the other
             allowable approval mechanisms cannot be employed in a
             timely fashion or for some other compelling reason. IESG
             Approval is not intended to circumvent the public review
             processes implied by other policies that could have been
             employed for a particular assignment.  IESG Approval would
             be appropriate, however, in cases where expediency is
             desired and there is strong consensus for making the
             assignment (e.g., WG consensus).

             The following guidelines are suggested for any evaluation
             under IESG Approval:

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              - The IESG can (and should) reject a request if another
                path for registration is available that is more
                appropriate and there is no compelling reason to use
                that path.

              - before approving a request, the community should be
                consulted, via a "call for comments" that provides as
                much information as is reasonably possible about the

   Examples: IPv4 Multicast address assignments [RFC3171], IPv4 IGMP
   Type and Code values [RFC3228], Mobile IPv6 Mobility Header Type and
   Option values [RFC3775].

   It should be noted that it often makes sense to partition a name
   space into multiple categories, with assignments within each category
   handled differently. For example, many protocols now partition name
   spaces into two (or even more) parts, where one range is reserved for
   Private or Experimental Use, while other ranges are reserved for
   globally unique assignments assigned following some review process.
   Dividing a name space into ranges makes it possible to have different
   policies in place for different ranges.

   Examples:  LDAP [RFC4520], Pseudowire Edge to Edge Emulation (PWE3)

4.2.  What To Put In Documents That Create A Registry

   The previous sections presented some issues that should be considered
   in formulating a policy for assigning values in name spaces. It is
   the Working Group and/or document author's job to formulate an
   appropriate policy and specify it in the appropriate document. In
   almost all cases, having an explicit "IANA Considerations" section is
   appropriate. The following and later sections define what is needed
   for the different types of IANA actions.

   Documents that create a new name space (or modify the definition of
   an existing space) and that expect IANA to play a role in maintaining
   that space (e.g., serving as a repository for registered values) MUST
   provide clear instructions on details of the name space. In
   particular, instructions MUST include:

     1) The name of the registry (or sub-registry) being created and/or
        maintained. The name will appear on the IANA web page and will
        be referred to in future documents that need to allocate a value
        from the new space. The full name (and abbreviation, if
        appropriate) should be provided. It is highly desirable that the

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        chosen name not be easily confusable with the name of another
        registry. When creating a sub-registry, the registry that it is
        a part of should be clearly identified. When referring to an
        already existing registry, providing a URL to precisely identify
        the registry is helpful. All such URLs, however, will be removed
        from the RFC prior to final publication. For example, documents
        could contain: [TO BE REMOVED: This registration should take
        place at the following location:]

     2) What information must be provided as part of a request in order
        to assign a new value. This information may include the need to
        document relevant security considerations, if any.

     3) The review process that will apply to all future requests for a
        value from the namespace.

        Note: 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 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 for media types),
        that mailing address should be specified. Note, however, that
        when mailing lists are specified, the requirement for a
        Designated Expert MUST also be specified (see Section 3).

        If 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.

     4) The size, format and syntax of registry entries. When creating a
        new name/number space, authors must describe any technical
        requirements on registry (and sub-registry) values (e.g., valid
        ranges for integers, length limitations on strings, etc.)  as
        well as the exact format that registry values should be
        displayed in.  For number assignments, one should specify
        whether values are to be recorded in decimal, hexadecimal or
        some other format. For strings, the encoding format should be
        specified (e.g., ASCII, UTF8, etc.) Authors should also clearly
        specify what fields to record in the registry.

     5) Initial assignments and reservations. Clear instructions should
        be provided to identify any initial assignments or
        registrations. In addition, any ranges that are to be reserved
        for "Private Use", "Reserved", "Unassigned", etc. should be
        clearly indicated.

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   When specifying the process for making future assignments, it is
   quite acceptable to pick one (or more) of the example policies listed
   in Section 4.1 and refer to it by name.  Indeed, this is the
   preferred mechanism in those cases where the sample policies provide
   the desired level of review. It is also acceptable to cite one of the
   above policies and include additional guidelines for what kind of
   considerations should be taken into account by the review process.
   For example, RADIUS [RFC3575] specifies the use of a Designated
   Expert, but includes specific additional criteria the Designated
   Expert should follow.

   For example, a document could say something like:

        This document defines a new DHCP option, entitled "FooBar" (see
        Section y), assigned a value of TBD1 from the DHCP Option space
        [to be removed upon publication:] [DHCP-

            Tag     Name            Length      Meaning
            ----    ----            ------      -------
            TBD1    FooBar          N           FooBar server

        The FooBar option also defines an 8-bit FooType field, for which
        IANA is to create and maintain a new sub-registry entitled
        "FooType values" under the FooBar option. Initial values for the
        DHCP FooBar FooType registry are given below; future assignments
        are to be made through Expert Review [IANA-CONSIDERATIONS].
        Assignments consist of a DHCP FooBar FooType name and its
        associated value.

            Value    DHCP FooBar FooType Name        Definition
            ----     ------------------------        ----------
            0        Reserved
            1        Frobnitz                        See Section y.1
            2        NitzFrob                        See Section y.2
            3-254    Unassigned
            255      Reserved

   For examples of documents that provide detailed guidance to IANA on
   the issue of assigning numbers, consult [RFC2929, RFC3575, RFC3968,

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4.3.  Updating IANA Guidelines For Existing Registries

   Updating the registration process for an already existing (i.e.,
   previously created) name space (whether created explicitly or
   implicitly) follows a process similar to that used when creating a
   new namespace. That is, a document is produced that makes reference
   to the existing namespace and then provides detailed guidelines for
   handling assignments in each individual name space. Such documents
   are normally processed as BCPs [IETF-PROCESS].

   Example documents that updated the guidelines for managing (then)
   pre-existing registries include: [RFC2929,RFC3228,RFC3575].

5.  Registering New Values In An Existing Registry

5.1.  What to Put In Documents When Registering Values

   Often, documents request an assignment from an already existing name
   space (i.e., one created by a previously-published RFC). In such

    - Documents should clearly identify the name space in which each
      value is to be registered. If the registration goes into a sub-
      registry, the author should clearly describe where the assignment
      or registration should go. It is helpful to use the exact name
      space name as listed on the IANA web page (and defining RFC), and
      cite the RFC where the name space is defined.

      Note 1: There is no need to mention what the assignment policy for
      new assignments is, as that should be clear from the references.

      Note 2: When referring to an existing registry, providing a URL to
      precisely identify the registry is helpful. Such URLs, however,
      should usually be removed from the RFC prior to final publication,
      since IANA URLs are not guaranteed to be stable in the future. In
      cases where it is important to include a URL in the document, IANA
      should should concur on its inclusion.

      As an example, documents could contain: [TO BE REMOVED: This
      registration should take place at the following location:]

    - Each value requested should be given a unique reference. When the
      value is numeric, use the notation: TBD1, TBD2, etc. Throughout
      the document where an actual IANA-assigned value should be filled
      in, use the "TBDx" notation. This helps ensure that the final RFC

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      has the correct assigned values inserted in in all of the relevant
      places where the value is expected to appear in the final
      document. For values that are text strings, a specific name can be
      suggested. IANA will normally assign the name, unless it conflicts
      with a name already in use.

    - Normally, the values to be used are chosen by IANA and documents
      should specify values of "TBD". However, in some cases a value may
      have been used for testing or in early implementations. In such
      cases, it is acceptable to include text suggesting what specific
      value should be used (together with the reason for the choice).
      For example, one might include the text "the value XXX is
      suggested as it is used in implementations". However, it should be
      noted that suggested values are just that; IANA will attempt to
      assign them, but may find that impossible, if the proposed number
      has already been assigned for some other use.

      For some registries, IANA has a longstanding policy prohibiting
      assignment of names or codes on a vanity or organization name
      basis, e.g., codes are always assigned sequentially unless there
      is a strong reason for making an exception.  Nothing in this
      document is intended to change those policies or prevent their
      future application.

    - The IANA Considerations section should summarize all of the IANA
      actions, with pointers to the relevant sections elsewhere in the
      document as appropriate. When multiple values are requested, it is
      generally helpful to include a summary table.  It is also helpful
      for this table to be in the same format as it should appear on the
      IANA web site. For example:

           Value     Description          Reference
           --------  -------------------  ---------
           TBD1      Foobar               [RFCXXXX]

      Note: in cases where authors feel that including the full table is
      too verbose or repetitive, authors should still include the table,
      but may include a note asking the table be removed prior to
      publication of the final RFC.

   As an example, the following text could be used to request assignment
   of a DHCPv6 option number:

      IANA has assigned an option code value of TBD1 to the DNS
      Recursive Name Server option and an option code value of TBD2 to
      the Domain Search List option from the DHCP option code space

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      defined in section 24.3 of RFC 3315.

5.2.  Updating Registrations

   Registrations are a request to assign a new value, 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 media 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 defining the namespace must clearly state
   who is responsible for maintaining and updating a registration. In
   different cases, it may be appropriate to specify one or more of the

      - 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, a Designated Expert or another entity as
        having the right to change the registrant associated with a
        registration and any requirements or conditions on doing so.
        This is mainly to get around the problem when a registrant
        cannot be reached in order to make necessary updates.

5.3.  Overriding Registration Procedures

   Since RFC 2434 was published, experience has shown that the
   documented IANA considerations for individual protocols do not always
   adequately cover the reality after the protocol is deployed. For
   example, many older routing protocols do not have documented,
   detailed IANA considerations. In addition, documented IANA
   considerations are sometimes found to be too stringent to allow even
   working group documents (for which there is strong consensus) to
   obtain code points from IANA in advance of actual RFC publication.
   In other cases, the documented procedures are unclear or neglected to
   cover all the cases. In order to allow assignments in individual
   cases where there is strong IETF consensus that an allocation should

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   go forward, but the documented procedures do not support such an
   assignment, the IESG is granted authority to approve assignments in
   such cases. The intention is not to overrule properly documented
   procedures, or to obviate the need for protocols to properly document
   their IANA Considerations. Instead, the intention is to permit
   assignments in individual cases where it is obvious that the
   assignment should just be made, but updating the IANA process just to
   assign a particular code point is viewed as too heavy a burden.

   In general, the IETF would like to see deficient IANA registration
   procedures for a namespace revised through the IETF standards
   process, but not at the cost of unreasonable delay for needed
   assignments. If the IESG has had to take the action in this section,
   it is a strong indicator that the IANA registration procedures should
   be updated, possibly in parallel with ongoing protocol work.

6.  Miscellaneous Issues

6.1.  When There Are No IANA Actions

   Before an Internet-Draft can be published as an RFC, IANA needs to
   know what actions (if any) it needs to perform. Experience has shown
   that it is not always immediately obvious whether a document has no
   IANA actions, without reviewing a document in some detail. In order
   to make it clear to IANA that it has no actions to perform (and that
   the author has consciously made such a determination!), such
   documents should include an IANA Considerations section that states:

      This document has no IANA Actions.

   This statement, or an equivalent form of words, must only be inserted
   after the WG or individual submitter has carefully verified it to be
   true. Using such wording as a matter of "boilerplate" or without
   careful consideration can lead to incomplete or incorrect IANA
   actions being performed.

   If a specification makes use of values from a name space that is not
   managed by IANA, it may be useful to note this fact, e.g., with
   wording such as:

      The values of the Foobar parameter are assigned by the Barfoo
      registry on behalf of the Rabfoo Forum. Therefore, this document
      has no IANA Actions.

   In some cases, the absence of IANA-assigned values may be considered
   valuable information for future readers; in other cases it may be

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   considered of no value once the document has been approved, and may
   be removed before archival publication. This choice should be made
   clear in the draft, for example by including a sentence such as

        [RFC Editor: please remove this section prior to publication.]


        [RFC Editor: please do not remove this section.]

6.2.  Namespaces Lacking Documented Guidance

   For all existing RFCs that either explicitly or implicitly rely on
   IANA to evaluate assignments without specifying a precise evaluation
   policy, IANA (in consultation with the IESG) will continue to decide
   what policy is appropriate. Changes to existing policies can always
   be initiated through the normal IETF consensus process.

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

6.3.  After-The-Fact Registrations

   Occasionally, IANA becomes aware that an unassigned value from a
   managed name space is in use on the Internet, or that an assigned
   value is being used for a different purpose than originally
   registered. IANA will not condone such misuse, i.e., procedures of
   the type described in this document MUST be applied to such cases. In
   the absence of specifications to the contrary, values may only be
   reassigned for a different purpose with the consent of the original
   assignee (when possible) and with due consideration of the impact of
   such a reassignment. In cases of likely controversy, consultation
   with the IESG is advised.

6.4.  Reclaiming Assigned Values

   Reclaiming previously-assigned values for reuse is tricky, because
   doing so can lead to interoperability problems with deployed systems
   still using the assigned values. Moreover, it can be extremely
   difficult to determine the extent of deployment of systems making use
   of a particular value.  However, in cases where the name space is
   running out of unassigned values and additional ones are needed, it
   may be desirable to attempt to reclaim unused values. When reclaiming
   unused values, the following (at a minimum) should be considered:

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    - attempts should be made to contact the original party to which a
      value is assigned, to determine if the value was ever used, and if
      so, the extent of deployment. (In some cases, products were never
      shipped or have long ceased being used. In other cases, it may be
      known that a value was never actually used at all.)

    - reassignments should not normally be made without the concurrence
      of the original requester. Reclamation under such conditions
      should only take place where there is strong evidence that a value
      is not widely used, and the need to reclaim the value outweighs
      the cost of a hostile reclamation. In any case, IESG approval is
      needed in this case.

    - it may be appropriate to write up the proposed action and solicit
      comments from relevant user communities. In some cases, it may be
      appropriate to write an RFC that goes through a formal IETF
      process (including IETF Last Call) as was done when DHCP reclaimed
      some of its "Private Use" options [RFC3942]

7.  Appeals

   Appeals on registration decisions made by IANA can be appealed using
   the normal IETF appeals process as described in  Section 6.5 of
   [IETF-PROCESS]. Specifically, appeals should be directed to the IESG,
   followed (if necessary) by an appeal to the IAB, etc.

8.  Mailing Lists

   All IETF mailing lists associated with evaluating or discussing
   assignment requests as described in this document are subject to
   whatever rules of conduct and methods of list management are
   currently defined by Best Current Practices or by IESG decision.

9.  Security Considerations

   Information that creates or updates a registration needs to be
   authenticated and authorized. IANA updates registries according to
   instructions in published RFCs and from the IESG. It also may accept
   clarifications from document authors, relevant WG chairs, Designated
   Experts and mail list participants too.

   Information concerning possible security vulnerabilities of a
   protocol may change over time. Likewise, security vulnerabilities

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   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 generally required for all
   protocols that make use of parameters (data types, operation codes,
   keywords, etc.) used in IETF protocols or registered by IANA.  Such
   security considerations are usually included in the protocol document
   [RFC3552].  It is the responsibility of the IANA Considerations
   associated with a particular registry to specify what (if any)
   security considerations must be provided when assigning new values,
   and the process for reviewing such claims.

10.  Changes Relative to RFC 2434

   Changes include:

    - Major reordering of text to expand descriptions and to better
      group topics such as "updating registries" vs. "creating new
      registries", in order to make it easier for authors to find the
      text most applicable to their needs.

    - Numerous editorial changes to improve readability.

    - Changed the term "IETF Consensus" to "IETF Review" and added more
      clarifications. History has shown that people see the words "IETF
      Consensus" (without consulting the actual definition) are quick to
      make incorrect assumptions about what the term means in the
      context of IANA Considerations.

    - Added "RFC Required" to list of defined policies.

    - Much more explicit directions and examples of "what to put in

    - "Specification Required" now implies use of Designated Expert to
      evaluate specs for sufficient clarity.

    - Significantly changed the wording in Section 3. Main purpose is to
      make clear that Expert Reviewers are accountable to the community,
      and to provide some guidance for review criteria in the default

    - Changed wording to remove any special appeals path. The normal
      RFC2026 appeals path is used.

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    - Added section about reclaiming unused value.

    - Added a section on after-the-fact registrations.

    - Added section indicating that mailing lists used to evaluate
      possible assignments (e.g., by a designated expert) are subject to
      normal IETF rules.

11.  IANA Considerations

   This document is all about IANA Considerations, but has no IANA

12.  Acknowledgments

   This document has benefited from specific feedback from Jari Arkko,
   Marcelo Bagnulo Braun, Brian Carpenter, Michelle Cotton, Barbara
   Denny, Spencer Dawkins, Miguel Garcia, Paul Hoffman, Russ Housley,
   John Klensin, Allison Mankin, Blake Ramsdell, Mark Townsley, Magnus
   Westerlund and Bert Wijnen.

   The original acknowledgments section in RFC 2434 was:

   Jon Postel and Joyce Reynolds provided a detailed explanation on what
   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].

13.  Normative References

   [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
                    Requirement Levels", BCP 14, RFC 2119, March 1997.

14.  Informative References

   [ASSIGNED] "Assigned Numbers: RFC 1700 is Replaced by an On-line
                    Database," J.  Reynolds, Ed., RFC 3232, January

   [DHCP-OPTIONS] Alexander, S. and R. Droms, "DHCP Options and BOOTP

draft-narten-iana-considerations-rfc2434bis-09.txt             [Page 23]
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                    Vendor Extensions", RFC 2132, March 1997.

   [DHCP-IANA] Procedures and IANA Guidelines for Definition of New DHCP
                    Options and Message Types. R. Droms, RFC 2939,
                    September 2000.

   [EXPERIMENTATION] "Assigning Experimental and Testing Numbers
                    Considered Useful". T.  Narten, RFC 3692, January

   [IANA-CONSIDERATIONS] Alvestrand, H. and T. Narten, "Guidelines for
                    Writing an IANA Considerations Section in RFCs", BCP
                    26, RFC 2434, October 1998.

   [IANA-MOU] Memorandum of Understanding Concerning the Technical Work
                    of the Internet Assigned Numbers Authority. B.
                    Carpenter, F. Baker, M.  Roberts, RFC 2860, June

   [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] S. Kent, K. Seo., "Security Architecture for the Internet
                    Protocol", RFC 4301, December 2005.

   [MIME-REG] "Media Type Specifications and Registration Procedures".
                    N. Freed, J. Klensin. December 2005, RFC 4288.

   [PROTOCOL-EXT] "Design Considerations for Protocol Extensions",
                    draft-carpenter-extension-recs-02.txt (Work in

   [RFC2929] Domain Name System (DNS) IANA Considerations. D. Eastlake
                    3rd, E.  Brunner-Williams, B. Manning. September

   [RFC3171] "IANA Guidelines for IPv4 Multicast Address Assignments".
                    Z.  Albanna, K. Almeroth, D. Meyer, M. Schipper.
                    August 2001.

   [RFC3228] IANA Considerations for IPv4 Internet Group Management
                    Protocol (IGMP). B. Fenner. February 2002.

   [RFC3552] Guidelines for Writing RFC Text on Security Considerations.
                    E.  Rescorla, B. Korver. July 2003.

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   [RFC3575] IANA Considerations for RADIUS (Remote Authentication Dial
                    In User Service). B. Aboba. RFC 3575, July 2003.

   [RFC3748] Extensible Authentication Protocol (EAP), B. Aboba, L.
                    Blunk, J.  Vollbrecht, J. Carlson, H. Levkowetz,
                    Ed., RFC 3748, June, 2004.

   [RFC3978] IETF Rights in Contributions. S. Bradner, Ed.. March 2005.

   [RFC3775] "Mobility Support in IPv6," D. Johnson, C. Perkins, J.
                    Arkko. June 2004.

   [RFC3932] The IESG and RFC Editor Documents: Procedures. H.
                    Alvestrand.  October 2004.

   [RFC3942] "Reclassifying Dynamic Host Configuration Protocol version
                    4 (DHCPv4) Options", B. Volz. RFC 3942, November

   [RFC3968] "The Internet Assigned Number Authority (IANA) Header Field
                    Parameter Registry for the Session Initiation
                    Protocol (SIP)," G. Camarillo. RFC 3968, December

   [RFC4005] "Diameter Network Access Server Application," P. Calhoun,
                    G. Zorn, D. Spence, D. Mitton. August 2005.

   [RFC4025] "A Method for Storing IPsec Keying Material in DNS," M.
                    Richardson.  March 2005.

   [RFC4044] "Fibre Channel Management MIB",  K. McCloghrie. May 2005.

   [RFC4124] "Protocol Extensions for Support of Diffserv-aware MPLS
                    Traffic Engineering," F. Le Faucheur, Ed.. June

   [RFC4169] "Hypertext Transfer Protocol (HTTP) Digest Authentication
                    Using Authentication and Key Agreement (AKA)
                    Version-2". V. Torvinen, J.  Arkko, M. Naslund.
                    November 2005.

   [RFC4271] "A Border Gateway Protocol 4 (BGP-4)," Y. Rekhter, Ed., T.
                    Li, Ed., S. Hares, Ed.. January 2006.

   [RFC4283] "Mobile Node Identifier Option for Mobile IPv6 (MIPv6)," A.
                    Patel, K. Leung, M. Khalil, H. Akhtar, K. Chowdhury.
                    November 2005.

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   [RFC4306] "Internet Key Exchange (IKEv2) Protocol", C. Kaufman, Ed.
                    December 2005

   [RFC4340] "Datagram Congestion Control Protocol (DCCP)," E. Kohler,
                    M.  Handley, S. Floyd. March 2006

   [RFC4366] "Transport Layer Security (TLS) Extensions," S. Blake-
                    Wilson, M.  Nystrom, D. Hopwood, J. Mikkelsen, T.
                    Wright. April 2006.

   [RFC4346] "The Transport Layer Security (TLS) Protocol Version 1.1,"
                    T.  Dierks, E. Rescorla. April 2006.

   [RFC4395] "Guidelines and Registration Procedures for New URI
                    Schemes," T.  Hansen, T. Hardie, L. Masinter.
                    February 2006.

   [RFC4422] "Simple Authentication and Security Layer (SASL)". A.
                    Melnikov, Ed., K. Zeilenga, Ed.. June 2006.

   [RFC4446] "IANA Allocations for Pseudowire Edge to Edge Emulation
                    (PWE3)," L.  Martini. April 2006.

   [RFC4520] "Internet Assigned Numbers Authority (IANA) Considerations
                    for the Lightweight Directory Access Protocol
                    (LDAP)," K. Zeilenga. June 2006.

   [RFC4589] "Location Types Registry," H. Schulzrinne, H. Tschofenig.
                    July 2006.

   [RFC4727] "Experimental Values In IPv4, IPv6, ICMPv4, ICMPv6, UDP,
                    and TCP Headers". B. Fenner. November 2006.

   [RFC4995] "The RObust Header Compression (ROHC) Framework," L-E.
                    Jonsson, G.  Pelletier, K. Sandlund. July 2007.

15.  Authors' Addresses

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

   Phone: 919-254-7798

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   Harald Tveit Alvestrand
   Beddingen 10
   Trondheim,   7014


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