It should be noted that it often makes sense to partition a name
   space into several categories, with assignments out of each category
   handled differently. For example, the DHCP option space [DHCP] is
   split into two parts. Option numbers in the range of 1-127 are
   globally unique and assigned according to the Specification Required
   policy described above, while options number 128-254 are "site
   specific", i.e., Local Use. Dividing the name space up makes it
   possible to allow some assignments to be made with minimal review,
   while simultaneously reserving some part of the space for future use.

3.  Registration maintenance

   Registrations are a request for an assigned number, including the
   related information needed to evaluate and document the request. Even
   after a number has been assigned, some types of registrations contain
   additional information that may need to be updated over time. For
   example, mime types, character sets, language tags, etc. typically
   include more information than just the registered value itself.
   Example information can include point of contact information,
   security issues, pointers to updates, literature references, etc.  In
   such cases, the document must clearly state who is responsible for
   maintaining and updating a registration. It is appropriate to:

      - 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
        registration.








 
RFC 2434           Guidelines for IANA Considerations       October 1998


      - Designate the IESG or another authority as having the right to
        reassign ownership of a registration. This is mainly to get
        around the problem when some registration owner cannot be
        reached in order to make necessary updates.

4.  What To Put In Documents

   The previous sections presented some issues that should be considered
   in formulating a policy for assigning well-known numbers and other
   protocol constants. It is the Working Group and/or document author's
   job to formulate an appropriate policy and specify it in the
   appropriate document. In some cases, having an "IANA Considerations"
   section may be appropriate. Specifically, documents that create an
   name space (or modify the definition of an existing space) and that
   expect the IANA to play a role in maintaining that space (e.g.,
   serving as a repository for registered values) MUST document the
   process through which future assignments are made.  Such a section
   MUST state clearly:

      - whether or not an application for an assigned number needs to be
        reviewed. If review is necessary, the review mechanism MUST be
        specified.  When a Designated Expert is used, documents MUST NOT
        name the Designated Expert in the document itself; instead, the
        name should be relayed to the appropriate IESG Area Director at
        the time the document is sent to the IESG for approval.

      - If the request should also be reviewed on a specific public
        mailing list (such as the ietf-types@iana.org for media types),
        that mailing address should be specified. Note, however, that
        use of a Designated Expert MUST also be specified.

      - if the IANA is expected to make assignments without requiring an
        outside review, sufficient guidance MUST be provided so that the
        requests can be evaluated with minimal subjectivity.

   Authors SHOULD attempt to provide guidelines that allow the IANA to
   assign new values directly without requiring review by a Designated
   Expert. This can be done easily in many cases by designating a range
   of values for direct assignment by the IANA while simultaneously
   reserving a sufficient portion of the name space for future use by
   requiring that assignments from that space be made only after a more
   stringent review.

   Finally, it is quite acceptable to pick one of the example policies
   cited above and refer to it by name.  For example, a document could
   say something like:






 
RFC 2434           Guidelines for IANA Considerations       October 1998


        Following the policies outlined in [IANA-CONSIDERATIONS],
        numbers in the range 0-63 are allocated as First Come First