



Network Working Group                                      A. Baber, Ed.
Internet-Draft                                           S. Tanamal, Ed.
Obsoletes: 8126 (if approved)                                       IANA
Intended status: Best Current Practice                    6 October 2025
Expires: 9 April 2026


     Guidelines for Writing an IANA Considerations Section in RFCs
                   draft-baber-ianabis-rfc8126bis-02

Abstract

   Many protocols make use of points of extensibility that use constants
   to identify various protocol parameters.  To ensure that the values
   in these fields do not have conflicting uses and to promote
   interoperability, their allocations are often coordinated by a
   central record keeper.  For IETF protocols, that role is filled by
   the Internet Assigned Numbers Authority (IANA).

   To make assignments in a given registry prudently, guidance
   describing the conditions under which new values should be assigned,
   as well as when and how modifications to existing values can be made,
   is needed.  This document defines a framework for the documentation
   of these guidelines by specification authors, in order to assure that
   the provided guidance for the IANA Considerations is clear and
   addresses the various issues that are likely in the operation of a
   registry.

   This is the fourth edition of this document; it obsoletes RFC 8126.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 9 April 2026.





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Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Keep IANA Considerations for IANA . . . . . . . . . . . .   4
     1.2.  For Updated Information . . . . . . . . . . . . . . . . .   5
     1.3.  A Quick Checklist Up Front  . . . . . . . . . . . . . . .   5
   2.  Creating and Revising Registries  . . . . . . . . . . . . . .   7
     2.1.  Organization of Registries  . . . . . . . . . . . . . . .   8
     2.2.  Documentation Requirements for Registries . . . . . . . .   9
     2.3.  Specifying Change Control for Registries and
           Registrations . . . . . . . . . . . . . . . . . . . . . .  12
     2.4.  Revising Existing Registries  . . . . . . . . . . . . . .  12
     2.5.  Adding Notes to Registries  . . . . . . . . . . . . . . .  13
   3.  Registering New Values in an Existing Registry  . . . . . . .  13
     3.1.  Documentation Requirements for Registrations  . . . . . .  13
     3.2.  Updating Existing Registrations . . . . . . . . . . . . .  16
     3.3.  Overriding Registration Procedures  . . . . . . . . . . .  16
     3.4.  Early Allocations . . . . . . . . . . . . . . . . . . . .  17
   4.  Choosing a Registration Policy and Well-Known Policies  . . .  17
     4.1.  Private Use . . . . . . . . . . . . . . . . . . . . . . .  21
     4.2.  Experimental Use  . . . . . . . . . . . . . . . . . . . .  21
     4.3.  Hierarchical Allocation . . . . . . . . . . . . . . . . .  22
     4.4.  First Come First Served . . . . . . . . . . . . . . . . .  23
     4.5.  Expert Review . . . . . . . . . . . . . . . . . . . . . .  24
     4.6.  Specification Required  . . . . . . . . . . . . . . . . .  25
     4.7.  RFC Required  . . . . . . . . . . . . . . . . . . . . . .  26
     4.8.  IETF Review . . . . . . . . . . . . . . . . . . . . . . .  26
     4.9.  Standards Action  . . . . . . . . . . . . . . . . . . . .  26
     4.10. IESG Approval . . . . . . . . . . . . . . . . . . . . . .  27
     4.11. With Expert Review  . . . . . . . . . . . . . . . . . . .  27
     4.12. Using the Well-Known Registration Policies  . . . . . . .  28
     4.13. Using Multiple Policies . . . . . . . . . . . . . . . . .  30
       4.13.1.  Range-Dependent Policies . . . . . . . . . . . . . .  30
       4.13.2.  Ensuring a Path for SDOs . . . . . . . . . . . . . .  30



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       4.13.3.  Provisional and Permanent Registrations  . . . . . .  31
       4.13.4.  Two-Tiered Registries  . . . . . . . . . . . . . . .  32
   5.  Designated Experts  . . . . . . . . . . . . . . . . . . . . .  33
     5.1.  The Motivation for Designated Experts . . . . . . . . . .  33
     5.2.  The Role of the Designated Expert . . . . . . . . . . . .  33
       5.2.1.  Managing Designated Experts in the IETF . . . . . . .  35
     5.3.  Designated Expert Reviews . . . . . . . . . . . . . . . .  35
     5.4.  Expert Reviews and the Document Lifecycle . . . . . . . .  37
   6.  Well-Known Registration Status Terminology  . . . . . . . . .  37
   7.  Documentation References in IANA Registries . . . . . . . . .  38
   8.  What to Do in "bis" Documents . . . . . . . . . . . . . . . .  39
     8.1.  Organizing "bis" Considerations . . . . . . . . . . . . .  39
     8.2.  Handling Existing References  . . . . . . . . . . . . . .  40
   9.  Miscellaneous Issues  . . . . . . . . . . . . . . . . . . . .  41
     9.1.  When There Are No IANA Actions  . . . . . . . . . . . . .  41
     9.2.  Namespaces Lacking Documented Guidance  . . . . . . . . .  42
     9.3.  After-the-Fact Registrations  . . . . . . . . . . . . . .  42
     9.4.  Reclaiming Assigned Values  . . . . . . . . . . . . . . .  42
     9.5.  Contact Person vs Assignee or Owner . . . . . . . . . . .  43
     9.6.  Closing or Obsoleting a Registry/Registrations  . . . . .  44
   10. Appeals . . . . . . . . . . . . . . . . . . . . . . . . . . .  45
   11. Mailing Lists . . . . . . . . . . . . . . . . . . . . . . . .  45
   12. IESG Responsibilities and Capabilities  . . . . . . . . . . .  46
   13. Registry Design Practices . . . . . . . . . . . . . . . . . .  46
     13.1.  Metadata Fields  . . . . . . . . . . . . . . . . . . . .  46
       13.1.1.  Status . . . . . . . . . . . . . . . . . . . . . . .  47
       13.1.2.  Recommended  . . . . . . . . . . . . . . . . . . . .  47
       13.1.3.  Notes  . . . . . . . . . . . . . . . . . . . . . . .  48
     13.2.  Registration Templates . . . . . . . . . . . . . . . . .  48
     13.3.  Module Files . . . . . . . . . . . . . . . . . . . . . .  48
     13.4.  Field-Specific Modification Procedures . . . . . . . . .  49
   14. Language and Formatting in the IANA Considerations Section  .  49
   15. Security Considerations . . . . . . . . . . . . . . . . . . .  50
   16. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  51
   17. References  . . . . . . . . . . . . . . . . . . . . . . . . .  51
     17.1.  Normative References . . . . . . . . . . . . . . . . . .  51
     17.2.  Informative References . . . . . . . . . . . . . . . . .  51
   Appendix A.  Changes Relative to Earlier Editions of BCP 26 . . .  58
     A.1.  2025: Changes in This Document Relative to RFC 8126 . . .  58
     A.2.  2016: Changes in This Document Relative to RFC 5226 . . .  59
     A.3.  2008: Changes in RFC 5226 Relative to RFC 2434  . . . . .  60
   Appendix B.  Acknowledgments  . . . . . . . . . . . . . . . . . .  61
     B.1.  Acknowledgments for This Document (2025)  . . . . . . . .  61
     B.2.  Acknowledgments for the Third Edition (2017)  . . . . . .  61
     B.3.  Acknowledgments from the Second Edition (2008)  . . . . .  61
     B.4.  Acknowledgments from the First Edition (1998) . . . . . .  62
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  62




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1.  Introduction

   Many protocols make use of points of extensibility that use constants
   to identify various protocol parameters.  To ensure that the values
   in these fields do not have conflicting uses and to promote
   interoperability, their allocations are coordinated by a central
   record keeper known as the Internet Assigned Numbers Authority (IANA)
   [RFC2860].  The Protocol field in the IP header [RFC0791] and media
   types [RFC6838] are two examples of such coordinations.

   In this document, we call the range of possible values for such a
   field a "namespace".  The binding or association of a specific value
   with a particular purpose within a namespace is called an assignment
   (or, variously: an assigned number, assigned value, code point,
   protocol constant, or protocol parameter).  The act of assignment is
   called a registration, and it takes place in the context of a
   registry.  The terms "assignment" and "registration" are used
   interchangeably throughout this document.

   To make assignments in a given namespace prudently, guidance
   describing the conditions under which new values should be assigned,
   as well as when and how modifications to existing values can be made,
   is needed.  This document defines a framework for the documentation
   of these guidelines by specification authors, in order to assure that
   the guidance for the IANA Considerations is clear and addresses the
   various issues that are likely in the operation of a registry.

   Typically, this information is recorded in a dedicated section of the
   specification with the title "IANA Considerations".

1.1.  Keep IANA Considerations for IANA

   The purpose of having a dedicated IANA Considerations section is to
   provide a single place to collect clear and concise information and
   instructions for IANA.  Technical documentation should reside in
   other parts of the document; the IANA Considerations should refer to
   these other sections by reference only (as needed).  Using the IANA
   Considerations section as primary technical documentation both hides
   it from the target audience of the document and interferes with
   IANA's review of the actions they need to take.

   An ideal IANA Considerations section clearly enumerates and specifies
   each requested IANA action; includes all information IANA needs, such
   as the full names of all applicable registries; and includes clear
   references to elsewhere in the document for other information.






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   The IANA actions are normally phrased as requests for, or
   instructions to, IANA (such as, "IANA is asked to assign the value
   TBD1 from the Frobozz registry..."); the RFC Editor will change those
   sentences to reflect the actions taken ("IANA has assigned the value
   83 from the Frobozz registry...").

1.2.  For Updated Information

   IANA maintains a web page at https://iana.org/help/protocol-
   registration that includes additional clarification information
   beyond what is provided here, such as minor updates and summary
   guidance.  Document authors should check that page.  Any significant
   updates to the best current practice will have to feed into updates
   to BCP 26 (this document), which is definitive.

1.3.  A Quick Checklist Up Front

   It's useful to be familiar with this document as a whole.  But when
   you return for quick reference, here are checklists for the most
   common things you'll need to do and references to help with the less
   common ones.

   In general...

   1.  Put all the information that IANA will need to know into the
       "IANA Considerations" section of your document (see Section 1.1).

   2.  Try to keep that section only for information to IANA and to
       designated expert reviewers; put significant technical
       information in the appropriate technical sections of the document
       (see Section 1.1).

   3.  Note that the IESG has the authority to resolve issues with IANA
       registrations (see Section 5.3).  If you have any questions or
       problems, you should consult your document shepherd and/or
       working group chair, who may ultimately involve an Area Director
       (see Section 3.3).  See Section 12 for more information on IESG
       responsibilities.

   4.  Contact IANA if you have any questions about writing an IANA
       Considerations section.  In particular, contact IANA if your
       document may need special IANA resources such as if IANA would
       have to host a new type of module, or coordinate with another
       organization, or process a high volume of registration requests,
       and so on.

   If you are creating a new registry...




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   1.  Give the registry a descriptive name and provide a brief
       description of its use (see Section 2.2).

   2.  Identify the registry group that it should be part of (see
       Section 2.1).  Your document might create a new registry group;
       that would need to be called out separately from the creation of
       the registries in the group.

   3.  Clearly specify the information required in order to register new
       items (see Section 2.2).  Be sure to specify data types, lengths,
       and valid ranges for fields.

   4.  Specify the initial set of items for the registry, if applicable
       (see Section 2.2).

   5.  Make sure the change control policy for the registry is clear to
       IANA, in case changes to the format or policies need to be made
       later (see Sections 2.3 and 9.5).

   6.  Select a registration policy -- or a set of policies -- to use
       for future registrations (see Section 4, and especially note
       Sections 4.12 and 4.13).

   7.  If you're using a policy that requires a designated expert
       (Expert Review or Specification Required), understand Section 5
       and provide review guidance to the designated expert (see
       Section 5.3).

   8.  If any items or ranges in your registry need to be reserved for
       special use or are otherwise unavailable for assignment, see
       Section 6.

   If you are registering into an existing registry...

   1.  Clearly identify the registry by its exact name and optionally by
       its URL (see Section 3.1).

   2.  If the registry has multiple ranges from which assignments can be
       made, make it clear which range is requested (see Section 3.1).

   3.  Unless an early allocation has already been secured, avoid using
       specific values for numeric or bit assignments, and let IANA pick
       a suitable value at registration time (see Section 3.1).  This
       will avoid registration conflicts among multiple documents.







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   4.  If you need an early assignment during document development, see
       [RFC7120].  If the registry does not require RFC publication, you
       can request values from IANA directly without invoking the
       process from RFC 7120.

   5.  For "reference" fields, use the document that provides the best
       and most current documentation for the item being registered.
       Include section numbers to make it easier for readers to locate
       the relevant text (see Sections 3.1 and 7).

   6.  Use both the IANA website and the registry's reference
       document(s) to determine what the registry requires so you can
       accurately provide all the necessary information (see
       Section 3.1).  In particular, documents published after the
       original one may add fields, change the registration
       requirements, or other such actions that would affect your
       registration.

   7.  Similarly, check for any special registry-specific rules or
       processes, such as posting to a particular mailing list for
       comment (see Section 3.1).

   8.  If the registration policy for the registry does not already
       dictate the change control policy, make sure to make the change
       control policy clear, in case the registration needs to be
       updated or modified later (see Section 9.5).

   If you're writing a "bis" document or otherwise making older
   documents obsolete, see Section 8.

   If you need to change the format/contents or policies for an existing
   registry, see Section 2.4.

   If you need to update an existing registration, see Section 3.2.

   If you need to close down a registry because it is no longer needed,
   see Section 9.6.

2.  Creating and Revising Registries

   Defining a registry involves describing the namespaces to be created,
   listing an initial set of assignments (if applicable), and
   documenting guidelines on how future assignments are to be made.

   When defining a registry, consider structuring the namespace in such
   a way that only top-level assignments need to be made with central
   coordination, and those assignments can delegate lower-level
   assignments so coordination for them can be distributed.  This



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   lessens the burden on IANA for dealing with assignments, and is
   particularly useful in situations where distributed coordinators have
   better knowledge of their portion of the namespace and are better
   suited to handling those assignments.

2.1.  Organization of Registries

   All registries are anchored from the IANA "Protocol Registries" page
   at https://www.iana.org/protocols.  That page lists registries in
   protocol category groups, placing related registries together and
   making it easier for users of the registries to find the necessary
   information.  Clicking on the title of one of the registries on the
   IANA Protocol Registries page will take the reader to the details
   page for that registry.


   Registry  A collection of entries whose assigned, available, and/or
      reserved values are presented in a single table.  Entries in the
      table may also be referred to as "assignments", "allocations"
      (that is, allocations from a pool of values), or "registrations"
      (a term that is more commonly applied to strings).  Entries
      consist of at least an identifier and a reference to a
      specification and/or one or more responsible parties.

   Registry group  A set of related registries that share a common base
      URL, with each registry distinguished by a fragment identifier.
      When creating a registry, document authors must tell IANA which
      registry group it belongs in, citing the name of the group and the
      base URL.  If no suitable group exists, the document must create
      one.  While most protocols require only a single registry group
      (which is typically named for the protocol and its abbreviation),
      multiple groups might be appropriate.  Protocol category groups
      listed in the "Protocol Registries" page typically map to a single
      registry group, but exceptions are possible.

   Subregistry  A registry "for" one or more registrations in a parent
      registry.  Examples include "Error Code 1 Subcodes," a subregistry
      for value 1 ("Common Header Parse Error") in the "GIST Error
      Codes" registry [RFC5971], and "Code Values for RADIUS Attribute
      241.1, Frag-Status" [RFC7499].

   In the past, documents have sometimes referred to registry groups as
   "top-level registries," or referred to the groups as "registries" and
   called all of the tables within them "subregistries."  However, the
   term "subregistry" is more useful as an indicator of a parent-child
   relationship between registries, and "top-level registry" suggests a
   sort of permanence or natural order that doesn't reflect the fact
   that working groups can choose to reorganize those groups.  With AD



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   approval, IANA can move registries and expand or delete groups,
   leaving tombstones and pointers as appropriate.  (If one URL replaces
   another, IANA will make sure the original will always redirect to the
   new one.)

   IANA strongly prefers that the registry of "Foo" types be named
   simply "Foo Types", rather than "Foo Type Registry".  A registry
   group for the BAR protocol should be named "Beyond All Recognition
   (BAR)" rather than "BAR Parameters."  An exception for the former
   might be made when, for example, several widely-used unofficial
   versions of the registry exist outside the IETF; it might be useful
   to indicate that the version on the IANA website is the official one.


2.2.  Documentation Requirements for Registries

   Documents that create a new namespace (or modify the definition of an
   existing space) and that expect IANA to play a role in maintaining
   that space (serving as a repository for registered values) must
   provide clear instructions on details of the namespace, either in the
   IANA Considerations section or referenced from it.

   Documents that come from the Independent Stream through the
   Independent Submissions Editor (ISE) may have special handling; see
   [RFC8726].

   In particular, such instructions must include:

   The name of the registry
      This name will appear on the IANA web page and will be referred to
      in future documents that allocate values from the new space.  The
      full name (which can include an acronym) must be provided; you
      cannot leave this to IANA to determine.

      It is highly desirable that the name not be easily confused with
      the name of another registry.  IANA's preferred solution is to use
      the protocol name as a prefix if possible.  Examples of registries
      that use this naming pattern include "TLS Cipher Suites", "MASQUE
      URI Suffixes", and "HTTP/2 Settings".  Each of these are part of a
      registry group which has the protocol name in the registry group
      name.

   The name of the registry group
      When creating a registry, the group that it is a part of must be
      identified by its full name.  See Section 2.1.

      Providing a URL that precisely identifies that group helps IANA
      understand the request.



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   Required information for registrations
      This tells registrants what information they have to include in
      their registration requests.  Some registries require only the
      requested value and a reference to a document where use of the
      value is defined.  Other registries require a more detailed
      registration template that describes relevant security
      considerations, internationalization considerations, and other
      such information.

      When a template is required, consider whether IANA should post
      every field from the template in the registry, or post only
      specified fields, or post only specified fields in the registry
      while also providing a link to the template (typically as a plain-
      text document) hosted on the IANA website.  Examples of the latter
      approach include the URI scheme [RFC7595] and media type [RFC6838]
      registries (at the time this document is published).

   Applicable registration policy
      The policy that will apply to all future requests for
      registration.  See Section 4.

   Size, format, and syntax of registry entries
      What fields to record in the registry, any technical requirements
      on registry entries (valid ranges for integers, length limitations
      on strings, and such), and the exact format in which registry
      values should be displayed.  For numeric assignments, one should
      specify whether values are to be recorded in decimal, in
      hexadecimal, or in some other format.

      Strings are expected to be ASCII, and it should be clearly
      specified whether case matters, and whether, for example, strings
      should be shown in the registry in uppercase or lowercase.

      Strings that represent protocol parameters will rarely, if ever,
      need to contain non-ASCII characters.  If non-ASCII characters are
      really necessary, instructions should make it very clear that they
      are allowed and that the non-ASCII characters should be
      represented as Unicode characters using the "(U+XXXX)" convention.
      Anyone creating such a registry should think carefully about this
      and consider internationalization advice such as that in
      [RFC7564], Section 10.

   Initial assignments and reservations
      Any initial assignments or registrations to be included.  In
      addition, any ranges that are to be reserved for "Private Use",
      "Reserved", "Unassigned", etc. (see Section 6) should be
      indicated.




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      If IANA is to assign numeric values, the IANA Considerations
      section must specify the range of values available for assignment,
      including the lower and upper bounds.  The text should say whether
      to use decimal, hexadecimal, binary, or octal representation.  The
      representation should be used consistently throughout the
      registry.

   For example, a document might specify a new registry by including:

   ---------------------------------------------------------------

   X. IANA Considerations

   This document defines a new DHCP option, entitled "FooBar" (see
   Section y), and assigns a value of TBD1 from the DHCP Option space
   <https://www.iana.org/assignments/bootp-dhcp-parameters>
   [RFC2132] [RFC2939]:
                                  Data
         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 registry titled
   "DHCP FooBar FooType Values."  Initial values for the
   DHCP FooBar FooType registry are given below; future assignments
   are to be made through Expert Review [BCP26].  Assignments consist
   of a DHCP FooBar FooType name and its associated value.

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

   For examples of documents that establish registries, consult
   [RFC9546], [RFC9516], and [RFC9454].











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2.3.  Specifying Change Control for Registries and Registrations

   Registry definitions and registrations within registries often need
   to be changed after they are created.  The process of making such
   changes is complicated when it is unclear who is authorized to make
   the changes.  For registries created by RFCs in the IETF stream,
   change control for the registry lies by default with the IETF, via
   the IESG.  The same is true for registrations made by IETF-stream
   RFCs.

   When a registry includes a "Change Controller," "Assignee," or
   "Registrant" field (or similar), going forward, IETF-stream RFC-based
   registrations should name the IETF, except where the reference
   document for the registry requires that the IESG be named instead (as
   in the port [RFC6335] and IETF XML [RFC3688] registries, among
   others).

   Because registries can be created and registrations can be made
   outside the IETF stream, it can sometimes be desirable to have change
   control outside the IETF and IESG, and clear specification of change
   control policies is always helpful.

   It is advised, therefore, that all registries that are created by
   documents outside of the IETF stream clearly specify a change control
   policy and a change controller.  It is also advised that registries
   that allow registrations from outside the IETF stream include, for
   each value, the designation of a change controller for that value.
   If the definition or reference for a registered value ever needs to
   change, or if a registered value needs to be deprecated, it is
   critical that IANA know who is authorized to make the change.  For
   example, the Media Types registry [RFC6838] includes a "Change
   Controller" in its registration template.  See also Section 9.5.

2.4.  Revising Existing Registries

   Updating the registration process or making changes to the format of
   an already existing (previously created) registry (whether created
   explicitly or implicitly) follows a process similar to that used when
   creating a new registry.  That is, a document is produced that makes
   reference to the existing namespace and then provides detailed
   guidance for handling assignments in the registry or detailed
   instructions about the changes required.









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   If a change requires a new column in the registry, the instructions
   need to be clear about how to populate that column for the existing
   registrations.  That populating might be by specifying the new
   entries itself or by setting a column-specific registration procedure
   (such as Expert Review) that allows the information to be assembled
   and provided to IANA after publication.  Other changes may require
   similar clarity.

   Registry modification requires approval from the change controller.
   Modifying a registry created by an IETF Stream RFC does not
   automatically require an IETF Stream RFC of the same type (e.g.
   Standards Track or Informational), but the change controller could
   choose to require it.

   Under some circumstances, such as with a straightforward change that
   is clearly needed (such as adding a "status" column), or when an
   earlier error needs to be corrected, the IESG may approve an update
   to a registry without requiring a new RFC.  Example documents that
   updated the guidelines for assignments in pre-existing registries
   include: [RFC6195], [RFC6929], and [RFC8615].

2.5.  Adding Notes to Registries

   Notes attached to the registry itself (as opposed to individual
   registrations) are often supplied by RFCs, but can also be added to
   the registry after publication, if the need becomes apparent.

   Notes or warnings concerning registry content, structure, or usage
   should be approved by an Area Director.  However, notes that tell
   users how to obtain resources from IANA (for example, how to use
   Rsync to retrieve module files) can be added without AD approval.

   When determining whether to add a note, consider whether some
   alternative or future action might be called for, either in addition
   to or instead of a note.  For example, if a note should be used to
   list the values that could appear in a field, consider who would be
   responsible for updating that note if the list were to change.  In
   some cases, it could be appropriate for an RFC to list those values
   instead, or even create a registry for them.

3.  Registering New Values in an Existing Registry

3.1.  Documentation Requirements for Registrations

   Often, documents request an assignment in an existing registry (one
   created by a previously published document).





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   Such documents should clearly identify the registry into which each
   value is to be registered.  Use the exact registry name as listed on
   the IANA web page, and cite the RFC where the registry is defined.
   When referring to an existing registry, providing a URL to precisely
   identify the registry is helpful (see Section 2.2).

   There is no need to mention what the assignment policy is when making
   new assignments in existing registries, as that should be clear from
   the references.  However, if multiple assignment policies might
   apply, as in registries with different ranges that have different
   policies, it is important to make it clear which range is being
   requested, so that IANA will know which policy applies and can assign
   a value in the correct range.

   Be sure to provide all the information required for a registration,
   and follow any special processes that are set out for the registry.
   Registries sometimes require the completion of a registration
   template for registration or ask registrants to post their request to
   a particular mailing list for discussion prior to registration.  Look
   up the registry's reference document: the required information and
   special processes should be documented there.

   Normally, numeric values to be used are chosen by IANA when the
   document is approved; drafts should not specify final values.
   Instead, placeholders such as "TBD1" and "TBD2" should be used
   consistently throughout the document, giving each item to be
   registered a different placeholder.  The RFC Editor will replace the
   placeholder names with the IANA-assigned values.  When drafts need to
   specify numeric values for testing or early implementations, they
   will either request early allocation (see Section 3.4) or use values
   that have already been set aside for testing or experimentation (if
   the registry in question allows that without explicit assignment).
   It is important that drafts not declare that specific numeric values
   will be assigned to them before IANA has actually made the
   assignments.  A draft can request a specific value in the IANA
   Considerations section, and IANA will accommodate such requests when
   possible, but the proposed number might have been assigned to some
   other use by the time the draft is approved.

   If a draft does request a specific value, the fact that the value has
   not been secured and could be assigned for another purpose before the
   draft has been approved should be indicated as clearly as possible.
   For example, if value "5" is preferred, and the value is presented in
   a table, it should be listed as "5 (suggested)" (Section 14).

   Normally, text-string values to be used are specified in the
   document, as collisions are less likely with text strings.  IANA will
   consult with the authors if there is, in fact, a collision, and a



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   different value has to be used.  When drafts need to specify string
   values for testing or early implementations, they sometimes use the
   expected final value.  But it is often useful to use a draft value
   instead, possibly including the draft version number.  This allows
   the early implementations to be distinguished from those implementing
   the final version.  A document that intends to use "foobar" in the
   final version might use "foobar-testing-draft-05" for the -05 version
   of the draft, for example.

   For some registries, there is a long-standing policy prohibiting
   assignment of names or codes on a vanity or organization-name basis.
   For example, codes might always be 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.

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

      IANA is asked to assign 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
      defined in Section 24.3 of RFC 3315.

   The IANA Considerations section should summarize all of the IANA
   actions, with pointers to the relevant sections elsewhere in the
   document as appropriate.  Including section numbers is especially
   useful when the reference document is large; the section numbers will
   make it easier for those searching the reference document to find the
   relevant information.

   When multiple values are requested, it is generally helpful to
   include a summary table of the additions/changes.  It is also helpful
   for this table to be in the same format as it appears or will appear
   on the IANA web site.  For example:

   Value     Description          Reference
   --------  -------------------  ---------
   TBD1      Foobar               this RFC, Section 3.2
   TBD2      Gumbo                this RFC, Section 3.3
   TBD3      Banana               this RFC, Section 3.4

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





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3.2.  Updating Existing Registrations

   Even after a number has been assigned, some types of registrations
   contain additional information that may need to be updated over time.

   For example, media types and URN namespaces [RFC8141] typically
   include more information than just the registered value itself, and
   may need updates to items such as point-of-contact information,
   security issues, pointers to updates, and literature references.

   In such cases, the document defining the namespace must clearly state
   who is responsible for maintaining and updating a registration.
   Depending on the registry, it may be appropriate to specify one or
   more of:

   *  Letting registrants and/or nominated change controllers update
      their own registrations, subject to the same constraints and
      review as with new registrations.

   *  Allowing attachment of comments to the registration.  This can be
      useful in cases where others have significant objections to a
      registration, but the author does not agree to change the
      registration.

   *  Designating the IETF (as represented by 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 ensures that necessary updates can
      be made even if the original registrant cannot be reached.

   Unless otherwise specified, the following will hold true:

   *  The applicable registration procedure will also serve as the
      modification procedure.

   *  Unless the registration was made by an RFC, IANA can confirm and
      approve requests to update contact and change controller
      information.  However, IANA may request advice from experts or
      Area Directors.

3.3.  Overriding Registration Procedures

   Experience has shown that the documented IANA considerations for
   individual protocols do not always adequately cover the reality of
   registry operation or are not sufficiently clear.  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 perform a registration in advance of actual RFC



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   publication.

   In order to allow assignments in such cases, the IESG is granted
   authority to override registration procedures and approve assignments
   on a case-by-case basis.

   The intention here is not to overrule properly documented procedures
   or to obviate the need for protocols to properly document their IANA
   considerations.  Rather, it is to permit assignments in specific
   cases where it is obvious that the assignment should just be made,
   but updating the IANA process beforehand is too onerous.

   When the IESG is required to take action as described above, it is a
   strong indicator that the applicable registration procedures should
   be updated, possibly in parallel with the work that instigated it.

   IANA always has the discretion to ask the IESG for advice or
   intervention when they feel it is needed, such as in cases where
   policies or procedures are unclear to them, where they encounter
   issues or questions they are unable to resolve, or where registration
   requests or patterns of requests appear to be unusual or abusive.

3.4.  Early Allocations

   IANA normally takes its actions when a document is approved for
   publication.  There are times, though, when early allocation of a
   value is important for the development of a technology, for example,
   when early implementations are created while the document is still
   under development.

   IANA has a mechanism for handling such early allocations in some
   cases.  See [RFC7120] for details.  It is usually not necessary to
   explicitly mark a registry as allowing early allocation, because the
   general rules will apply.

   It is not ordinarily possible to create registries before a document
   has been approved for publication.  IANA is reviewing a procedure
   that will allow make early registry creation available to working
   groups that need to update a registry that appears in a yet-to-be-
   approved draft with registrations that cannot be recorded in that
   draft.

4.  Choosing a Registration Policy and Well-Known Policies

   %% NOTE FOR IANABIS: The Specification Required procedure has not yet
   been updated.  Notes and questions have been collected and updated
   below.%%




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   "Specification Required" questions and notes:

   *  If the RFC for the registry doesn't specifically state that I-Ds
      are valid for Specification Required registrations, would opening
      registration to I-Ds require a new RFC, or can the expert simply
      consult with the group?  (After the publication of RFC 5226, if
      the RFC for the registry didn't address the question, the
      determination was left to the experts.)

   *  Archiving/storage issues still under discussion.

   *  When referencing an I-D, IANA points to the version that was
      current when the codepoint was registered, rather than pointing to
      the entire series.  It might be appropriate to note this in a
      separate reference-related section, as FCFS, Expert Review, and
      RFC 7120 Early Allocation registrations can also point to I-Ds.

   *  How does early allocation work for SDOs?  Who determines whether
      the organization qualifies?  Is this a lightweight one-year
      process with no renewals?  What does an expired allocation look
      like?  Does the expert keep track of expiration dates, or IANA?
      Who keeps track of document publication?

   Common Availability Issues:

   *  In some cases, an organization outside the IETF may not be able
      publish a final specification until IANA assigns values.  If the
      experts approve and the organization agrees, IANA can point to a
      published draft until the final document is available.

   *  In the absence of a final published version of the document, if
      they are satisfied that the specification will be published, the
      expert can approve a temporary early allocation under some
      circumstances [details pending].  Some RFCs also allow for
      permanent early registration, as in [RFC8392], Section 9.1.

   *  If the expert approves early registration, the expert is
      responsible for notifying IANA that the final version of the
      document has been published or, alternatively, that the
      registrations should be deprecated, obsoleted, or removed. [see
      deprecation/obsoletion section]

   *  If the specification is available only for purchase, the
      organization must provide a free copy for the expert to review.
      However, if a purchase-only specification is inappropriate for
      that registry or proposed registration, the expert can reject the
      request and require a freely-available specification.




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   %% END NOTES %%

   A registration policy is the policy that controls how new assignments
   in a registry are accepted.  There are several issues to consider
   when defining the registration policy.

   If the registry's namespace is limited, assignments will need to be
   made carefully to prevent exhaustion.

   Even when the space is essentially unlimited, it is still often
   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 (existing company names, for
      example).

   *  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 (for example, an existing assignment for an
      essentially equivalent service already exists).  IANA cannot
      review requests or specifications for technical content.

   Perhaps most importantly, unreviewed extensions can impact
   interoperability and security.  See [RFC6709].

   When the namespace is essentially unlimited and there are no
   potential interoperability or security issues, assigned numbers can
   usually be given out to anyone without any subjective review.  In
   such cases, IANA can make assignments directly, provided that IANA is
   provided all of the information necessary to screen requests without
   the application of technical expertise or subjective judgment.

   When this is not the case, some level of review is required.
   However, it's important to balance adequate review and ease of
   registration.  In many cases, those making registrations will not be
   IETF participants; requests often come from other standards
   organizations, from organizations not directly involved in standards,
   from ad-hoc community work (from an open-source project, for
   example), and so on.  Registration must not be unnecessarily
   difficult, unnecessarily costly (in terms of time and other
   resources), nor unnecessarily subject to denial.





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   While it is sometimes necessary to restrict what gets registered
   (e.g., for limited resources such as bits in a byte, or for items for
   which unsupported values can be damaging to protocol operation), in
   many cases having what's in use represented in the registry is more
   important.  Overly strict review criteria and excessive cost (in time
   and effort) discourage people from even attempting to make a
   registration.  If a registry fails to reflect the protocol elements
   actually in use, it can adversely affect deployment of protocols on
   the Internet, and the registry itself is devalued.

   Therefore, it is important to think specifically about the
   registration policy, and not just pick one arbitrarily nor copy text
   from another document.  Working groups and other document developers
   should use care in selecting appropriate registration policies when
   their documents create registries.  They should select the least
   strict policy that suits a registry's needs, and look for specific
   justification for policies that require significant community
   involvement (those stricter than Expert Review or Specification
   Required, in terms of the well-known policies).  The needs here will
   vary from registry to registry, and, indeed, over time, and this BCP
   will not be the last word on the subject.

   The following policies are defined for common usage.  These cover a
   range of typical policies that have been used to describe the
   procedures for assigning new values in a namespace.  It is not
   strictly required that documents use these terms; the actual
   requirement is that the instructions to IANA be clear and
   unambiguous.  However, use of these terms is strongly recommended
   because their meanings are widely understood.  Newly-minted policies,
   including ones that combine the elements of procedures associated
   with these terms in novel ways, may be used if none of these policies
   are suitable; it will help the review process if an explanation is
   included as to why that is the case.  The terms are fully explained
   in the following subsections.

      1.   Private Use
      2.   Experimental Use
      3.   Hierarchical Allocation
      4.   First Come First Served
      5.   Expert Review
      6.   Specification Required
      7.   RFC Required
      8.   IETF Review
      9.   Standards Action
      10.  IESG Approval






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   It should be noted that it often makes sense to partition a namespace
   into multiple categories, with assignments within each category
   handled differently.  Many protocols now partition namespaces into
   two or more parts, with one range reserved for Private or
   Experimental Use while other ranges are reserved for globally unique
   assignments assigned following some review process.  Dividing a
   namespace into ranges makes it possible to have different policies in
   place for different ranges and different use cases.

   Similarly, it will often be useful to specify multiple policies in
   parallel, with each policy being used under different circumstances.
   For more discussion of that topic, see Section 4.13.

   Examples of RFCs that specify multiple policies in parallel:

      LDAP [RFC4520]
      TLS ClientCertificateType Identifiers [RFC5246] (as detailed in
      the subsections below)
      MPLS Pseudowire Types Registry [RFC4446]

4.1.  Private Use

   Private Use is 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.  IANA does not record assignments from registries
   or ranges with this policy (and therefore there is no need for IANA
   to review 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 [RFC2939]
      Fibre Channel Port Type Registry [RFC4044]
      TLS ClientCertificateType Identifiers 224-255 [RFC5246]

4.2.  Experimental Use

   Experimental Use is similar to Private Use, but with the purpose
   being to facilitate experimentation.  See [RFC3692] for details.
   IANA does not record assignments from registries or ranges with this
   policy (and therefore there is no need for IANA to review them) and
   assignments are not generally useful for broad interoperability.
   Unless the registry explicitly allows it, it is not appropriate for
   documents to select explicit values from registries or ranges with
   this policy.  Specific experiments will select a value to use during



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   the experiment.

   When code points are set aside for Experimental Use, it's important
   to make clear any expected restrictions on experimental scope.  For
   example, say whether it's acceptable to run experiments using those
   code points over the open Internet or whether such experiments should
   be confined to more closed environments.  See [RFC6994] for an
   example of such considerations.

   Example:

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

4.3.  Hierarchical Allocation

   With Hierarchical Allocation, delegated administrators are given
   control over part of the namespace and can assign values in that part
   of the namespace.  IANA makes allocations in the higher levels of the
   namespace according to one of the other policies.

   Examples:

   *  DNS names - IANA manages the top-level domains (TLDs), and, as
      [RFC1591] says:

         Under each TLD may be created a hierarchy of names.  Generally,
         under the generic TLDs the structure is very flat.  That is,
         many organizations are registered directly under the TLD, and
         any further structure is up to the individual organizations.

   *  Object Identifiers - defined by ITU-T recommendation X.208.
      According to the informal site at http://www.alvestrand.no/
      objectid, some registries include

      -  IANA, which hands out OIDs under the "Private Enterprises"
         branch,
      -  ANSI, which hands out OIDs under the "US Organizations" branch,
         and
      -  BSI, which hands out OIDs under the "UK Organizations" branch.

   *  URN namespaces - IANA registers URN Namespace IDs (NIDs
      [RFC8141]), and the organization registering an NID is responsible
      for allocations of URNs within that namespace.







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4.4.  First Come First Served

   For the First Come First Served policy, 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 point of
   contact (including an email address, and sometimes a postal address)
   and a brief description of how the value will be used.  Additional
   information specific to the type of value requested may also need to
   be provided, as defined by the namespace.  For numbers, IANA
   generally assigns the next in-sequence unallocated value, but other
   values may be requested and assigned if an extenuating circumstance
   exists.  With names, specific text strings can usually be requested.

   IANA will add a change controller field to all registries that use
   the First Come First Served procedure.  Having a change controller
   for each entry for these types of registrations makes authorization
   of future modifications more clear.  See Section 2.3.

   It is important that changes to the registration of a First Come
   First Served code point retain compatibility with the current usage
   of that code point, so changes need to be made with care.  IANA
   cannot review change requests for content, but will check that the
   request has been authorized by the change controller's listed contact
   or the change controller itself, and the change controller should
   not, in most cases, be requesting incompatible changes nor
   repurposing a registered code point.  See also Sections 9.4 and 9.5.

   A working group or any other entity that is developing a protocol
   based on a First Come First Served code point has to be extremely
   careful that the protocol retains wire compatibility with current use
   of the code point.  Once that is no longer true, the new work needs
   to change to a different code point (and register that use at the
   appropriate time).

   It is also important to understand that First Come First Served
   really has no filtering.  Essentially, any well-formed request is
   accepted.

   If a specification needs to be checked for any quality other than
   availability, the First Come First Served procedure is not
   appropriate, and the Specification Required procedure (which includes
   an expert review) should be used instead.  If registration should
   require only a lightweight review, the document's instructions to the
   designated experts should note this.

   Examples:



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      SASL mechanism names [RFC4422]
      LDAP Protocol Mechanisms and LDAP Syntax [RFC4520]

4.5.  Expert Review

   For the Expert Review policy, review and approval by a designated
   expert (see Section 5) is required.  While this does not necessarily
   require formal documentation, information needs to be provided with
   the request for the designated expert to evaluate.  The registry's
   definition needs to make clear to registrants what information is
   necessary.  The actual process for requesting registrations is
   administered by IANA (see Section 1.2 for details).

   (This policy was also called "Designated Expert" in earlier editions
   of this document.  The current term is "Expert Review".)

   The document must provide clear guidance for the the designated
   expert, ideally in a dedicated subsection that describes
   documentation requirements (if any) and review criteria.  It is
   particularly important to lay out what should be considered when
   performing an evaluation and reasons for rejecting a request.

   It is also a good idea to include, when possible, a sense of whether
   many registrations are expected over time, or if the registry is
   expected to be updated infrequently or in exceptional circumstances
   only.

   Thorough understanding of Section 5 is important when deciding on an
   Expert Review policy and designing the guidance to the designated
   expert.

   Good examples of guidance to designated experts:

      Extensible Authentication Protocol (EAP) [RFC3748], Sections 6 and
      7.2
      North-Bound Distribution of Link-State and TE Information Using
      BGP [RFC7752], Section 5.1

   IANA will add a change controller field to all registries that use
   the Expert Review procedure.  See Section 2.3.

   Examples:

      EAP Method Types [RFC3748]
      HTTP Digest AKA algorithm versions [RFC4169]
      URI schemes [RFC7595]
      GEOPRIV Location Types [RFC4589]




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4.6.  Specification Required

   For the Specification Required policy, review and approval by a
   designated expert (see Section 5) is required, and the values and
   their meanings must be documented in a permanent and readily
   available public specification, in sufficient detail so that
   interoperability between independent implementations is possible.
   This policy is the same as Expert Review, with the additional
   requirement of a formal public specification.  In addition to the
   normal review of such a request, the designated expert will review
   the public specification and evaluate whether it is sufficiently
   stable and permanent, and sufficiently clear and technically sound 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, including informal
   documentation.

   For RFC publication, formal review by the designated expert is still
   requested, but the normal RFC review process is expected to provide
   the necessary review for interoperability.  The designated expert's
   review is still important, but it's equally important to note that
   when there is IETF consensus, the expert can sometimes be "in the
   rough" (see also the last paragraph of Section 5.4).

   As with Expert Review (Section 4.5), clear guidance to the designated
   expert should be provided when defining the registry, and thorough
   understanding of Section 5 is important.

   When specifying this policy, just use the term "Specification
   Required".  Some specifications have chosen to refer to it as "Expert
   Review with Specification Required", and that only causes confusion.

   Examples:

      Diffserv-aware TE Bandwidth Constraints Model Identifiers
      [RFC4124]
      TLS ClientCertificateType Identifiers 64-223 [RFC5246]
      ROHC Profile Identifiers [RFC5795]








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4.7.  RFC Required

   With the RFC Required policy, the registration request, along with
   associated documentation, must be published in an RFC.  The RFC need
   not be in the IETF stream, but may be in any RFC stream (currently an
   RFC may be in the IETF, IRTF, IAB, or Independent Submission streams
   [RFC5742]).

   Unless otherwise specified, any type of RFC is sufficient (currently
   Standards Track, BCP, Informational, Experimental, or Historic).

   Examples:

      DNSSEC DNS Security Algorithm Numbers [RFC6014]
      Media Control Channel Framework registries [RFC6230]
      DANE TLSA Certificate Usages [RFC6698]

4.8.  IETF Review

   (Formerly called "IETF Consensus" in the first edition of this
   document.)  With the IETF Review policy, new values are assigned only
   through RFCs in the IETF Stream -- those that have been shepherded
   through the IESG as AD-Sponsored or IETF working group documents
   [RFC2026] [RFC5378], have gone through IETF Last Call, and have been
   approved by the IESG as having IETF consensus.

   The intent is that the document and proposed assignment will be
   reviewed by the IETF community (including appropriate IETF working
   groups, directorates, and other experts) and by the IESG, to ensure
   that the proposed assignment will not negatively affect
   interoperability or otherwise extend IETF protocols in an
   inappropriate or damaging manner.

   Unless otherwise specified, any type of RFC is sufficient (currently
   Standards Track, BCP, Informational, Experimental, or Historic).

   Examples:

      IPSECKEY Algorithm Types [RFC4025]
      Accounting-Auth-Method AVP values in DIAMETER [RFC4005]
      TLS Extension Types [RFC5246]

4.9.  Standards Action

   For the Standards Action policy, values are assigned only through
   Standards Track or Best Current Practice RFCs in the IETF Stream.

   Examples:



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      BGP message types [RFC4271]
      Mobile Node Identifier option types [RFC4283]
      TLS ClientCertificateType Identifiers 0-63 [RFC5246]
      DCCP Packet Types [RFC4340]

4.10.  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
   the discretion to request documents or other supporting materials on
   a case-by-case basis.

   IESG Approval is not intended to be used often or as a "common case";
   indeed, it has seldom been used in practice.  Rather, it is intended
   to be available in conjunction with other policies as a fallback
   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 (such as from a working group) for making the
   assignment.

   Before approving a request, the IESG might consider consulting the
   community, via a "call for comments" that provides as much
   information as is reasonably possible about the request.

   Examples:

      Assigned Internet Protocol Numbers [RFC5237]
      IPv4 IGMP Type and Code values [RFC3228]
      Mobile IPv6 Mobility Header Type and Option values [RFC6275]

4.11.  With Expert Review

   IANA does not ordinarily ask IESG-designated registry experts to
   review requests for registration in "Standards Action," "IETF
   Review," "RFC Required," and "IESG Approval" registries.  If a
   registry requires both expert review and either RFC publication or
   IESG approval, the following expert-augmented hybrid procedures are
   available:

   *  Standards Action With Expert Review

   *  IETF Review With Expert Review

   *  RFC and Expert Review Required



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   *  IESG Approval With Expert Review

   As described in Section 5.4, IANA will initiate the expert review
   request during IETF Last Call or, if applicable, the document's
   conflict review.  If the IESG and the expert disagree, the IESG can
   choose to override the expert.

   If the submission is intended for direct approval for the IESG, as
   described in Section 12, IANA will submit the request to both the
   expert and the IESG.

   Most registries that require RFC publication do not require an
   additional expert review.  An expert-augmented procedure might be
   appropriate, however, if registry designers want to be sure that a
   specialist checks every proposal for intra-registry consistency,
   particularly if the relevant working group is unable to review it.

   Examples:

   "ACE Groupcomm Policies" [RFC9594]

   "Option Codes" (DHCPv6) [RFC8415]

4.12.  Using the Well-Known Registration Policies

   Because the well-known policies benefit from both community
   experience and wide understanding, their use is encouraged, and the
   creation of new policies needs to be accompanied by reasonable
   justification.

   It is also acceptable to cite one or more well-known policies and
   include additional guidelines for what kind of considerations should
   be taken into account by the review process.

   For example, for media-type registrations [RFC6838], a number of
   different situations are covered that involve the use of IETF Review
   and Specification Required, while also including specific additional
   criteria the designated expert should follow.  This is not meant to
   represent a registration procedure, but to show an example of what
   can be done when special circumstances need to be covered.

   The well-known policies from "First Come First Served" to "Standards
   Action" specify a range of policies in increasing order of strictness
   (using the numbering from the full list in Section 4):

   4.  First Come First Served

      No review, minimal documentation.



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   5 and 6  (of equal strictness).

      5.  Expert Review

         Expert review with sufficient documentation for review.

      6.  Specification Required

         Significant stable public documentation sufficient for
         interoperability.

   7.  RFC Required

      Any RFC publication, IETF or a non-IETF Stream.

   8.  IETF Review

      RFC publication, IETF Stream only, but need not be Standards
      Track.

   9.  Standards Action

      RFC publication, IETF Stream, Standards Track or BCP only.

   Examples of situations that might merit IETF Review or Standards
   Action include the following:

   *  When a resource is limited, such as bits in a byte (or in two
      bytes, or four), or numbers in a limited range.  In these cases,
      allowing registrations that haven't been carefully reviewed and
      agreed to by community consensus could too quickly deplete the
      allowable values.

   *  When thorough community review is necessary to avoid extending or
      modifying the protocol in ways that could be damaging.  One
      example is in defining new command codes, as opposed to options
      that use existing command codes: the former might require a strict
      policy, where a more relaxed policy could be adequate for the
      latter.  Another example is in defining protocol elements that
      change the semantics of existing operations.

   *  When there are security implications with respect to the resource,
      a thorough review is needed to ensure that the new usage is sound.
      Examples of this include lists of acceptable hashing and
      cryptographic algorithms, and assignment of transport ports in the
      system range.





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   When reviewing a document that asks IANA to create a new registry or
   change a registration policy to any policy more stringent than Expert
   Review or Specification Required, the IESG should ask for
   justification to ensure that more relaxed policies have been
   considered and that the more strict policy is the right one.

   Accordingly, document developers need to anticipate this and document
   their considerations for selecting the specified policy (ideally, in
   the document itself; failing that, in the shepherd writeup).
   Likewise, the document shepherd should ensure that the selected
   policies have been justified before sending the document to the IESG.

   When specifications are revised, registration policies should be
   reviewed in light of experience since the policies were set.

4.13.  Using Multiple Policies

   If some assignments within a registry should be easier to obtain than
   others, multiple registation procedures may be appropriate.

   For example:

   *  In large numeric registries, stricter procedures can apply only to
      the most desirable ranges.

   *  If registration is intended for the IETF or other SDOs but not
      individuals, the process can depend on the submitter.

   *  When the values are strings or some entries are "provisional," a
      field or label can indicate the review level for each
      registration.

4.13.1.  Range-Dependent Policies

   The most common application for multiple registration policies is to
   make assignments from different ranges of numeric values more or less
   difficult to obtain.  For example, if a registry's available values
   range from 0-65535, authors might assign a strict registration policy
   to values 0-255 and one or two lightweight policies (like First Come
   First Served) to the remaining values.  (Along with an Experimental
   or Private Use reservation, if appropriate.)

4.13.2.  Ensuring a Path for SDOs

   If IETF registrants should be required to produce an RFC, but
   registration should still be open to other standards organizations,
   two approaches are available:




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   *  A single "Specification Required" policy that applies to all
      requests.  This adds a overhead for RFC-based registrations, which
      do not ordinarily require review by a designated expert, but would
      be subjected to one here.  In addition, this policy would open
      registration to every RFC stream and type, which may not be the
      intention.

   *  Two policies that apply to the same set of available values: "IETF
      Review" or "Standards Action" for registrations made via the IETF
      process (or "RFC Required," if other streams are also
      appropriate), and "Specification Required" for requests submitted
      by other organizations.  Any issues concerning submitter
      eligibility should be described in the instructions to the expert.
      %% NOTE TO IANABIS: the possiblity of limiting registration to
      SDOs was brought up in 8126, Section 4.12, but criteria were not
      defined there, and have not (yet?) been defined here. %%

4.13.3.  Provisional and Permanent Registrations

   Some existing registries have policies that allow provisional
   registration: see URI Schemes [RFC7595] and Message Header Fields
   [RFC3864].  Registrations that are designated as provisional are
   usually defined as being more readily created, changed, reassigned,
   moved to another status, or removed entirely.  URI Schemes, for
   example, allow provisional registrations to be made with incomplete
   information.

   Allowing provisional registration ensures that the primary goal of
   maintaining a registry -- avoiding collisions between incompatible
   semantics -- is achieved without the side effect of "endorsing" the
   protocol mechanism the provisional value is used for.  Provisional
   registrations for codepoints that are ultimately standardized can be
   promoted to permanent status.  The criteria that are defined for
   converting a provisional registration to permanent will likely be
   more strict than those that allowed the provisional registration.

   If your registry does not have a practical limit on codepoints,
   perhaps adding the option for provisional registrations might be
   right for that registry as well.  See QUIC Frame Types [RFC9000].

   The provisional option can be implemented by splitting the registry
   into separate "Permanent" and "Provisional" registries or by adding a
   "Status" field (or similar) that can be filled in with a "Permanent"
   or "Provisional" label.  You might also consider whether provisional
   registrations should be accompanied by links to plain-text
   registration templates, given that they're less likely to be
   documented in RFCs, or whether certain registry fields should apply
   only to one type of registration.



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4.13.4.  Two-Tiered Registries

   When the registry needs to allow both IETF-reviewed and "simple"
   (e.g., First Come First Served) registrations, but 1) the
   registrations consist of strings rather than numeric values, 2) the
   level of review cannot be indicated by the content of the strings
   (e.g., the strings cannot be prefixed with "x-" or "vnd."), and 3) it
   isn't appropriate to describe the simple registrations as
   "Provisional," one of these two methods might be used:

   *  Create separate registries, each of which indicates the level of
      review in its title: "IETF-Approved Fruit Strings," for example,
      and "First Come First Served Fruit Strings."

   *  Create a registry that uses a dedicated field, like the "Status"
      field in the provisional/permanent registry model, to indicate the
      level of review applied to the registration.  This field might be
      called something like "RegAuth," and it could be filled in with
      values like "IETF" and "Simple" (or "Informal" or "Non-IETF").

   An "IETF" registration could use any procedure that requires an IETF
   Stream document: Standards Action, IETF Review, a bespoke process
   that requires an IETF Stream document as its base (for example, a
   process that requires or forbids a certain type of RFC, such as
   Informational), or one of those procedures with an Expert Review add-
   on.

   The IANA Considerations section could use text like this:

   This registry is open to both IETF-reviewed registrations and
   "simple" registrations that are not reviewed for technical
   content. The registry's "RegAuth" field will describe each
   registration as "IETF" or "Simple."

   The following RFC 8126 registration procedures will be applied
   to "IETF" and "Simple" registrations:

   RegAuth   Registration Procedure
   --------  ----------------------
   IETF      Standards Action
   Simple    First Some First Served

   The registry will list IETF registrations first.

   This approach could also be used to mark registrations that received
   some other level of review, such as review by a designated expert.





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   Alternatively, IETF/non-IETF entries could be distinguished by
   omitting the RegAuth field and placing the Change Controller field in
   a prominent location.

5.  Designated Experts

5.1.  The Motivation for Designated Experts

   Mailing list discussions can provide valuable technical input, but
   they often lack clear resolution, and IANA cannot monitor all lists
   or assess consensus.  Therefore, IANA relies on designated experts to
   evaluate requests and recommend whether assignments should be made.

   It should be noted that a key motivation for having designated
   experts is for the IETF to provide IANA with a subject matter expert
   to whom the evaluation process can be delegated.  IANA forwards
   requests to the expert, who provides a recommendation.  Registrants
   typically do not interact directly with experts unless the expert
   initiates contact (with IANA in copy, if they wish for IANA to retain
   records of the details of the request).  Each registry lists its
   designated experts.

   It will often be useful to use a designated expert only some of the
   time, as a supplement to other processes.  For more discussion of
   that topic, see Section 4.13.

5.2.  The Role of the Designated Expert

   The designated expert is responsible for coordinating the appropriate
   review of an assignment request.  The review may be wide or narrow,
   depending on 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, 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] and [RFC3575] for
   specific examples.

   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 such as those in Section 5.3.  Designated experts are generally
   not expected to be "gatekeepers", setting out to make registrations
   difficult to obtain, unless the guidance in the defining document
   specifies that they should act as such.  Absent stronger guidance,



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   the experts should be evaluating registration requests for
   completeness, interoperability, and conflicts with existing protocols
   and options.

   It has proven useful to have multiple designated experts for some
   registries.  Sometimes those experts work together in evaluating a
   request, while in other cases additional experts serve as backups,
   acting only when the primary expert is unavailable.  In registries
   with a pool of experts, the pool may have a single chair responsible
   for defining how requests are to be assigned to and reviewed by
   experts.  If a registry receives a relatively high volume of
   requests, IANA might assign requests to individual members in
   sequential or approximate random order.  More often, IANA will send
   requests to the group of experts, and consider the review complete
   when a certain number of replies have been received, as specified by
   the group itself.  The document defining the registry can, if it's
   appropriate for the situation, specify how the group should work --
   for example, it might be appropriate to specify rough consensus on a
   mailing list, within a related working group or among a pool of
   designated experts.

   In cases of disagreement among multiple 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, such as deadlock, the designating
   body may need to step in to resolve the problem.

   When designated experts have a conflict of interest for a particular
   review (if they are, for example, authors or significant proponents
   of a specification related to the registration under review), those
   experts should recuse themselves.  In the event that all the
   designated experts are conflicted, they should ask that a temporary
   expert be designated for the conflicted review.  The responsible AD
   may then handle the review or appoint someone to take it.

   This document defines the designated expert mechanism with respect to
   documents in the IETF stream only.  If other streams want to use
   registration policies that require designated experts, it is up to
   those streams (or those documents) to specify how those designated
   experts are appointed and managed.  What is described below, with
   management by the IESG, is only appropriate for the IETF stream.










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5.2.1.  Managing Designated Experts in the IETF

   Designated experts for registries created by the IETF are appointed
   by the IESG, normally upon recommendation by the relevant Area
   Director.  They may be appointed at the time a document creating or
   updating a namespace is approved by the IESG, or subsequently, when
   the first registration request is received.  Because experts
   originally appointed may later become unavailable, the IESG will
   appoint replacements as necessary.  The IESG may remove any
   designated expert that it appointed, at its discretion.

   The normal appeals process, as described in [RFC2026], Section 6.5.1,
   applies to issues that arise with the designated expert team.  For
   this purpose, the designated expert team takes the place of the
   working group in that description.

5.3.  Designated Expert Reviews

   In the years since [RFC2434] was published and 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
      the period specified by the IANA MoU with the IETF (currently 30
      days), either with a response or with a reasonable explanation for
      the delay (some requests may be particularly complex), IANA must
      raise the issue with the IESG.  If a designated expert being non-
      responsive recurs often, it causes problems by delaying
      evaluations and assignments.  In such a case, the IESG should take
      appropriate actions to ensure that the expert understands and
      accepts his or her 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.




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   When a designated expert is used, the documentation should give clear
   guidance to the designated expert, laying out criteria for performing
   an evaluation and reasons for rejecting a request.  In the case where
   there are no specific documented criteria, the presumption should be
   that a code point should be granted unless there is a compelling
   reason to the contrary (and see also Section 5.4).  Reasons that have
   been used to deny requests have included these:

   *  Scarcity of code points, where the finite remaining code points
      should be prudently managed, or where a request for a large number
      of code points is made and a single code point is the norm.

   *  Documentation is not of sufficient clarity to evaluate or ensure
      interoperability.

   *  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
      interoperability.

   Documents must not name the designated expert(s) in the document
   itself; instead, any suggested names should be relayed to the
   appropriate Area Director at the time the document is sent to the
   IESG for approval.  This is usually done in the document shepherd
   writeup.

   If the request should also be reviewed on a specific public mailing
   list, its address should be specified.










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5.4.  Expert Reviews and the Document Lifecycle

   Review by the designated expert is necessarily done at a particular
   point in time and represents review of a particular version of the
   document.  Unless the authors or chairs have already requested and
   obtained registration, IANA will initiate reviews during IETF Last
   Call.  And while rereviews might be done when it's acknowledged that
   the documentation of the registered item has changed substantially,
   making sure that rereview happens requires attention and care.

   It is possible, through carelessness, accident, inattentiveness, or
   even willful disregard, that changes might be made after the
   designated expert's review and approval that would, if the document
   were rereviewed, cause the expert not to approve the registration.
   It is up to the IESG, with the token held by the responsible Area
   Director, to be alert to such situations and to recognize that such
   changes need to be checked.

   When a registration requested by a document requires expert review,
   the review by the designated expert needs to be timely, submitted
   before the IESG evaluates the document.  The IESG should generally
   not hold the document up waiting for a late review.  It is also not
   intended for the expert review to override IETF consensus: the IESG
   should consider the review in its own evaluation, as it would do for
   other Last Call reviews.

6.  Well-Known Registration Status Terminology

   The following labels describe the status of an assignment or range of
   assignments:

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

      Experimental:  Available for general experimental use as described
            in [RFC3692].  IANA does not record specific assignments for
            any particular use.

      Unassigned:  Not currently assigned, and available for assignment
            via documented procedures.  While it's generally clear that
            any values that are not registered are unassigned and
            available for assignment, it is sometimes useful to
            explicitly specify that situation.  Note that this is
            distinctly different from "Reserved".

      Reserved:  Not assigned and not available for assignment.





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            Reserved values are held for special uses, such as to extend
            the namespace when it becomes exhausted.  "Reserved" is also
            sometimes used to designate values that had been assigned
            but are no longer in use, keeping them set aside as long as
            other unassigned values are available.  Note that this is
            distinctly different from "Unassigned".

            Reserved values can be released for assignment by the change
            controller for the registry (this is often the IETF, as
            represented by the IESG, for registries created by RFCs in
            the IETF stream).

            %% QUESTION FOR IANABIS: Are the next two new paragraphs
            sufficient/appropriate? %%

            Reserved values may be specified further as "Reserved for
            Private Use," "Reserved for Experimental Use," or "Reserved
            for Future Extension".  (Historically, many codepoints
            reserved for future extension have not been given any
            special label beyond "Reserved.")

            When reserving a codepoint, consider whether deprecation or
            obsoletion would be more appropriate.  See [RFC3692].

      Known Unregistered Use:  It's known that the assignment or range
            is in use without having been defined in accordance with
            reasonable practice.  Documentation for use of the
            assignment or range may be unavailable, inadequate, or
            conflicting.  This is a warning against use, as well as an
            alert to network operators who might see these values in use
            on their networks.

7.  Documentation References in IANA Registries

   Usually, registries and registry entries include references to
   documentation (RFCs or other documents).  The purpose of these
   references is to provide pointers for implementors to find details
   necessary for implementation, NOT to simply note what document
   created the registry or entry.  Therefore:

   *  If a document registers an item that is defined and explained
      elsewhere, the registered reference should be to the document
      containing the definition, not to the document that is merely
      performing the registration.







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   *  If the registered item is defined and explained in the current
      document, it is important to include sufficient information to
      enable implementors to understand the item and to create a proper
      implementation.

   *  If the registered item is explained primarily in a specific
      section of the reference document, it is useful to include a
      section reference.  For example, "[RFC4637], Section 3.2", rather
      than just "[RFC4637]".

   *  For documentation of a new registry, the reference should provide
      information about the registry itself, not just a pointer to the
      creation of it.  Useful information includes the purpose of the
      registry, a rationale for its creation, documentation of the
      process and policy for new registrations, guidelines for new
      registrants or designated experts, and other such related
      information.  But note that, while it's important to include this
      information in the document, it needn't all be in the IANA
      Considerations section.  See Section 1.1.

8.  What to Do in "bis" Documents

   On occasion, an RFC is issued that obsoletes a previous edition of
   the same document.  We sometimes call these "bis" documents, such as
   when RFC 4637 is to be obsoleted by draft-ietf-foo-rfc4637bis.  When
   the original document created registries and/or registered entries,
   there is a question of how to handle the IANA Considerations section
   in the "bis" document.

8.1.  Organizing "bis" Considerations

   When reviewing a "bis" document that obsoletes an earlier document,
   IANA has two concerns: 1) identifying new actions, and 2) determining
   whether existing references need to be replaced.

   Some authors choose to replicate all or part of the original
   document's IANA Considerations section.  However, new actions edited
   into existing text can be hard to identify.  Documents that take this
   approach should provide a subsection called "New IANA Actions."  This
   can be a brief list or summary, and it could include pointers to
   tables or other parts of the section, if those details can't be moved
   from another location.  This subsection should also tell IANA how to
   treat references to existing registrations, as described in
   Section 8.2.

   If the entire IANA Considerations section should be reproduced,
   consider placing it in an "RFC XXXX IANA Considerations" subsection.




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   When deciding how much, if any, of the original document's IANA
   Considerations section to include in a new IANA Considerations
   section, consider what the registry user might be looking for.

   If the original document included registration instructions, for
   example, and the new document does not, an applicant unfamiliar with
   RFC obsoletion might not guess that there were instructions to find.
   If you don't want to repeat information provided in the earlier
   document, the IANA Considerations section should at least point users
   to the appropriate section in that document.

8.2.  Handling Existing References

   If the original document is being obsoleted, the IANA Considerations
   must account for all references to it in the IANA registries and
   specify whether those references should be replaced.  However, the
   section does not have to name the individual registries and
   registrations.  If any should remain untouched, name those.  If the
   list of registrations that is being updated is shorter, it is
   acceptable to just name those instead.

   More detail may be required if section numbers associated with the
   original references need to be updated.

   The new document may also have to account for registrations that
   don't appear in the original document.  The source of these "extra"
   references is typically a later RFC that registered a codepoint, but
   listed that older RFC in the reference field instead of listing
   itself.  IANA can supply a list of registry groups that contain
   references to the original document.  For IANA, simply stating that
   references in that group should or should not be updated is
   sufficient.

   An example of a document that tells IANA how to update or deprecate
   existing references and registrations is [RFC9012]. %% NOTE TO
   IANABIS: More examples may be added here. %%

   In general, if the registrations specify the original document as a
   reference, those registrations should be updated to point to the
   current (not obsolete) documentation for those items.  Usually, that
   will mean changing the reference to be the "bis" document.

   If references should not be updated, consider whether IANA should
   also label those registrations "obsolete" or "deprecated."  IANA will
   list the new document as an additional reference, but leave the
   original reference in place.





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   It is extremely important to be clear in your instructions regarding
   updating references, especially in cases where some references need
   to be updated and others do not.

   If information for registered items has been or is being moved to
   other documents, then the registration information should be changed
   to point to those other documents.  In most cases, documentation
   references should not be left pointing to the obsoleted document for
   registries or registered items that are still in current use.  For
   registries or registered items that are no longer in current use, it
   will usually make sense to leave the references pointing to the old
   document -- the last current reference for the obsolete items.  The
   main point is to make sure that the reference pointers are as useful
   and current as is reasonable, and authors should consider that as
   they write the IANA Considerations for the new document.  As always:
   do the right thing, and there is flexibility to allow for that.

   While references to obsoleted documents are typically replaced,
   references to updated documents are often left intact.  However,
   authors should check any references to the updated document in the
   registries.

9.  Miscellaneous Issues

9.1.  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 the 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, after the authors confirm that this is the case,
   include an IANA Considerations section that states:

      This document has no IANA actions.

   IANA prefers that these "empty" IANA Considerations sections be left
   in the document for the record: it makes it clear later on that the
   document explicitly said that no IANA actions were needed (and that
   it wasn't just omitted).










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9.2.  Namespaces Lacking Documented Guidance

   For all existing RFCs that either explicitly or implicitly rely on
   IANA to make assignments without specifying a precise assignment
   policy, IANA will work with the IESG to decide what policy is
   appropriate.  Changes to existing policies can always be initiated
   through the normal IETF consensus process, or through the IESG when
   appropriate.

   All future RFCs that either explicitly or implicitly rely on IANA to
   register or otherwise administer namespace assignments must provide
   guidelines for administration of the namespace.

9.3.  After-the-Fact Registrations

   Occasionally, the IETF becomes aware that an unassigned value from a
   namespace is in use on the Internet or that an assigned value is
   being used for a different purpose than it was registered for.  The
   IETF does not condone such misuse; procedures of the type described
   in this document need to be applied to such cases, and it might not
   always be possible to formally assign the desired value.  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.

   This is part of the reason for the advice in Section 3.1 about using
   placeholder values, such as "TBD1", during document development:
   problems are often caused by the open use of unregistered values
   after results from well-meant, early implementations, where the
   implementations retained the use of developmental code points that
   never proceeded to a final IANA assignment.

9.4.  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 namespace 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.  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].

   *  It may be useful to differentiate between revocation, release, and
      transfer.  Revocation occurs when IANA removes an assignment in
      accordance with IETF instructions (whether the source is the IESG,
      a designated expert, working group chairs, or a document); release
      occurs when the assignee initiates that removal; and transfer
      occurs when either revocation or release is coupled with immediate
      reassignment.  It may be useful to specify procedures for each of
      these or to explicitly prohibit combinations that are not desired.

9.5.  Contact Person vs Assignee or Owner

   Many registries include designation of a technical or administrative
   contact associated with each entry.  Often, this is recorded as
   contact information for an individual.  It is unclear, though, what
   role the individual has with respect to the registration: is this
   item registered on behalf of the individual, the company the
   individual worked for, or perhaps another organization the individual
   was acting for?

   This matters because some time later, when the individual has changed
   jobs or roles, and perhaps can no longer be contacted, someone might
   want to update the registration.  IANA has no way to know what
   company, organization, or individual should be allowed to take the
   registration over.  For registrations rooted in RFCs, the stream
   owner (such as the IESG or the IAB) can make an overriding decision.
   But in other cases, there is no recourse.






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   Registries can include, in addition to a "Contact" field, an
   "Assignee" or "Owner" field (also referred to as "Change Controller")
   that can be used to address this situation, giving IANA clear
   guidance as to the actual owner of the registration.  This is
   strongly advised for all registries that might ever be open to
   assignments to parties outside of the IETF, and IANA has begun to
   automatically add a change controller field for registries that use
   the First Come First Served (Section 4.4), Expert Review
   (Section 4.5), and Specification Required (Section 4.6) policies.
   Alternatively, if no change controller field is present,
   organizations can put an organizational role into the "Contact" or
   "Reference" field in order to make their ownership clear.

9.6.  Closing or Obsoleting a Registry/Registrations

   %% NOTE TO IANABIS: This document should define what "deprecated" and
   "obsolete" mean. %%

   Sometimes there is a request to "close" a registry to further
   registrations.  When a registry is closed, no further registrations
   will be accepted.  The information in the registry will still be
   valid, and registrations already in the registry can still be
   updated.

   A closed registry can also be marked as "obsolete", as an indication
   that the information in the registry is no longer in current use.

   When a registry is closed or declared obsolete, IANA will update its
   registration procedure field to indicate that the registry has been
   closed and list the document that closes it as an additional
   reference for the registry itself, without removing any existing
   reference(s).  The document can also provide a note to be added to
   the registry by IANA, such as if the document authors have additional
   useful information about the change.

   Specific entries in a registry can be marked as "obsolete" (no longer
   in use) or "deprecated" (use is not recommended).

   Unless instructed to do otherwise, IANA will not re-assign deprecated
   or obsolete values until all other available values have been
   exhausted.

   Such changes to registries and registered values are subject to
   normal change controls (see Section 2.3).  Any closure, obsolescence,
   or deprecation serves to annotate the registry involved; the
   information in the registry remains there for informational and
   historic purposes.




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10.  Appeals

   Appeals of protocol parameter registration decisions can be made
   using the normal IETF appeals process as described in [RFC2026],
   Section 6.5.  That is, an initial appeal should be directed to the
   IESG, followed (if necessary) by an appeal to the IAB.

11.  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.

   Registry experts may benefit from a registration-specific mailing
   list where they can discuss requests.  Lists can be set up where the
   participants are just the designated experts, the experts plus
   applicants, or the whole community.  In general, the following should
   be taken into account:

   *  Name a mailing list to be created by the IETF.  (IANA does not
      create or maintain mailing lists.)  An existing IETF list can be
      used, but consider whether the traffic would be problematic in
      either direction (too much noise, too many requests).

   *  Consider whether the list should be limited to experts or open to
      the public.  Most expert review mailing lists are open.

   *  Set a deadline by which an expert should notify IANA that a
      request has been approved, barring complications.  Three weeks is
      a common deadline.

   *  Keep in mind that IANA does not monitor expert review mailing
      lists.  Consider whether applicants should be instructed to submit
      their requests to IANA instead of the mailing list.  In such
      cases, IANA would forward the request to the list with the
      applicant in copy.  Alerting IANA to the existence of the request
      at the outset means that IANA can watch for signs of inactivity
      and send reminders to non-responsive expert groups.

   *  When a document that creates a list tells applicants to write
      directly to the list instead of IANA, IANA posts a note in the
      registry that directs users to the list and tells them to contact
      IANA if they don't receive a response by the deadline cited in the
      document.  However, not all applicants will consult the registry
      before submitting an application.

   Examples:



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      CBOR Web Token (CWT) expert review mailing list [RFC8392]
      TLS expert review mailing list [RFC8447]

12.  IESG Responsibilities and Capabilities

   The following describes the registry-related actions the IESG must
   perform:

   *  Represent the IETF as change controller: Section 2.3

   *  Review registration requests that require direct IESG approval:
      Section 4.10

   *  Designate and manage experts: Section 5

   *  Review IANA Considerations sections, keeping in mind that IANA
      cannot determine whether a given set of registration procedures is
      appropriate for a new registry.  For a discussion of common
      procedures, see Section 4.

   The following describes the actions the IESG can take when needed,
   along with circumstances when such intervention might be appropriate:

   *  Modify existing registries: Section 2.4

   *  Override registration procedures: Section 3.3

   *  Advise and direct IANA as needed on topics such as unusual
      requests, missing instructions, unreachable change controllers:
      Section 3.3, Section 9.2, Section 9.3, and Section 9.4

13.  Registry Design Practices

   %% NOTE TO IANABIS: This section is not complete.  The purpose of the
   section is to make authors aware of registry design practices that
   they might not have seen before. %%

13.1.  Metadata Fields

   "Status," "Recommended," and "Notes" fields are often added to
   registries after they've been created.  Creating one (or more) before
   the need becomes apparent not only saves time, but can prompt future
   applicants, experts, and authors to add useful information that they
   otherwise might not have seen a place for.







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13.1.1.  Status

   %% NOTE TO IANABIS: Should this be collapsed into %%

   In some cases, it may be useful to include a "Status" field that
   reflects the operational or administrative state of each entry.
   However, there is currently no single agreed-upon set of possible
   status entries.  Some registries use this field to indicate whether
   registrations should be considered "provisional," "permanent,"
   "deprecated," or "obsolete," although the last two states are more
   often added to a registration's name or description field.

   Examples of registries that use a "Status" field:

      https://www.iana.org/assignments/email-auth
      https://www.iana.org/assignments/message-headers
      https://www.iana.org/assignments/rsip-parameters

13.1.2.  Recommended

   If it's appropriate to indicate whether registered items are
   recommended, consider whether "yes" and "no" answers are sufficient.
   It might also be appropriate to add a note to the registry that
   describes the meaning and/or limitations of each possible state.

   For example, the "Recommended" field in the TLS Cipher Suites
   registry can be filled in with one of three values: briefly, "Y" for
   "yes"; "N," which can mean only that review or applicability has been
   limited, not that use is broadly discouraged; or "D," which does
   discourage use.  [I-D.ietf-tls-rfc8447bis] defines those options in
   greater detail and provides a note to be added to each affected
   registry.

   Fields of this type can also be used to indicate whether usage is
   required, or whether a recommendation is context-specific.  Examples
   include the "Use for DNSSEC Signing" and "Implement for DNSSEC
   Signing" fields, among others, in the "DNS Security Algorithm
   Numbers" registry updated by [I-D.ietf-dnsop-rfc8624-bis].

   Examples:

      https://www.iana.org/assignments/tls-parameters
      https://www.iana.org/assignments/dns-sec-alg-numbers

   %% QUESTION FOR IANABIS: Should this section discuss whether to apply
   RFC 2119 language in a recommendation/requirement field? %%





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13.1.3.  Notes

   IANA recommends adding a "Notes" field to any registry.  Designated
   experts and Area Directors can approve updates to any registration's
   "Notes" field, even when modifying other aspects of the registration
   requires a specification.

13.2.  Registration Templates

   In some cases, an appropriate registration template can require
   applicants to fill in more fields than a table can easily display.
   If all of the template information should be published, IANA could
   post it as a text file and add link it to the registration.  Examples
   include media type and provisional URI scheme registrations:

      https://www.iana.org/assignments/media-types
      https://www.iana.org/assignments/uri-schemes

13.3.  Module Files

   IANA hosts MIB, YANG, and SID module files.  If hosting a new type of
   module would be useful and possible, the RFC should provide answers
   to at least the following questions:

   *  Can modules be updated after creation, or would they be replaced?

   *  Will IANA update the module in accordance with registrations,
      modifications, and/or status changes?  IANA-specific instructions
      should be included in or referenced from the IANA Considerations
      section.  (Note that IANA likely would not have expertise in this
      area.)

   *  Do authors or IANA need to be aware of special considerations for
      revision statements, references, or other fields?  For example, if
      a module includes reference information that appears in an
      underlying First Come First Served registry, how would that module
      treat a reference that consists solely of a name and contact
      information?

   *  How will modules be validated?

   *  IANA typically performs registry actions when a document is sent
      to the RFC Editor for processing, but posts new YANG modules after
      RFC publication.  How and when will modules be provided to IANA?

   For an example, see [I-D.ietf-netmod-rfc8407bis], "Guidelines for
   Authors and Reviewers of Documents Containing YANG Data Models."




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13.4.  Field-Specific Modification Procedures

   If necessary, a separate registration procedure (Section 4) can be
   applied to a single field.  Typically, this field-specific procedure
   will be less strict than the procedure required to receive an
   assignment.

   This approach could be useful in scenarios like these:

   *  A new column in a registry that requires RFC publication will have
      to be backfilled, but the requirement isn't urgent, and the
      information has yet to be compiled.  If other parties are
      amenable, assigning the "Expert Review" procedure to the column
      would make it possible to populate that column later without
      producing another RFC.

   *  Registrants may need to update a "Date" column in a registry that
      ordinarily requires expert approval.  Because this is considered a
      trivial update, modifications to that field could be implemented
      by IANA on a First Come First Served basis, as in the "QUIC
      Versions" registry [RFC9000].

   *  Alternatively, while codepoints with "Recommended" values
      initially set to "N" might be registered via a procedure like
      Specification Required, changing that value to "Y" might require
      an RFC published in the IETF stream.

14.  Language and Formatting in the IANA Considerations Section

   IANA doesn't require a specific format, but the following
   recommendations might simplify the writing process and result in a
   cleaner section:

   Subsections:
      Consider using using one or more levels of subsection to group and
      separate actions that affect different registry groups and
      registries.  Subsections can also be useful for setting off and
      creating distinct references for registration templates,
      instructions to designated experts, and, if necessary, brief
      summaries or discussions of the action.  (Note: if the document
      will obsolete an earlier RFC, see Section 8.)

   Verb Tense:
      Don't use past tense to describe registry actions unless they've
      already been completed.  The RFC Editor can convert future tense
      to past tense during the editing process.

   Requests vs. Instructions:



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      "IANA is requested to perform action X" and "IANA will perform
      action X" are both fine.

   Tables:
      TBD

   URLs:
      For registry users' convenience, any registry name should be
      accompanied by the base URL for the registry group.  For the QUIC
      group, for example, the base URL is
      https://www.iana.org/assignments/quic.

   Suggested Values:
      Naming preferred values before IANA assigns them is strongly
      discouraged.  If early allocation is impossible or undesirable,
      however, and specific values must be suggested in the document,
      authors should make it as clear as possible -- not for IANA's
      sake, but for the sake of potential implementors -- that the value
      may not be available by the time the document reaches the
      publication process.  Possible approaches to suggesting value 7,
      for example, include

      TBD1 (7 suggested)

      If the value has to be inserted into a table that has limited
      space, a shorter option could be

      TBD7

      The value should not be presented as "7" in a table, even if text
      outside the table indicates that the value is only being
      requested.

   While IANA is the primary audience, the section should also be clear
   enough for registry users who need to find registration instructions
   or confirm the source of a registration.

15.  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 may also accept
   clarifications from document authors, relevant working group chairs,
   designated experts, and mail list participants.

   Information concerning possible security vulnerabilities of a
   protocol may change over time.  Likewise, security vulnerabilities
   related to how an assigned number is used may change as well.  As new



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   vulnerabilities are discovered, information about such
   vulnerabilities may need to be attached to existing registrations so
   that users are not misled as to the true security issues surrounding
   the use of a registered number.

   Security needs to be considered as part of the selection of a
   registration policy.  For some protocols, registration of certain
   parameters will have security implications, and registration policies
   for the relevant registries must ensure that requests get appropriate
   review with those security implications in mind.

   An analysis of security issues is generally required for all
   protocols that make use of parameters (data types, operation codes,
   keywords, etc.) documented in IETF protocols or registered by IANA.
   Such security considerations are usually included in the protocol
   document [BCP72].  It is the responsibility of the IANA
   considerations associated with a particular registry to specify
   whether value-specific security considerations must be provided when
   assigning new values and the process for reviewing such claims.

16.  IANA Considerations

   Sitewide, IANA will replace references to RFC 8126 with references to
   this document.

   IANA will create a "Change Controller" field for all new registries
   that use the First Come First Served, Expert Review, and
   Specification Required registries.  In the future, IANA will also add
   empty Change Controller fields to existing registries that use those
   procedures but lack that field.

17.  References

17.1.  Normative References

   [RFC2026]  Bradner, S., "The Internet Standards Process -- Revision
              3", BCP 9, RFC 2026, DOI 10.17487/RFC2026, October 1996,
              <https://www.rfc-editor.org/info/rfc2026>.

17.2.  Informative References

   [BCP72]    Best Current Practice 72,
              <https://www.rfc-editor.org/info/bcp72>.
              At the time of writing, this BCP comprises the following:







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              Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552,
              DOI 10.17487/RFC3552, July 2003,
              <https://www.rfc-editor.org/info/rfc3552>.

              Gont, F. and I. Arce, "Security Considerations for
              Transient Numeric Identifiers Employed in Network
              Protocols", BCP 72, RFC 9416, DOI 10.17487/RFC9416, July
              2023, <https://www.rfc-editor.org/info/rfc9416>.

   [RFC0791]  Postel, J., "Internet Protocol", STD 5, RFC 791,
              DOI 10.17487/RFC0791, September 1981,
              <https://www.rfc-editor.org/info/rfc791>.

   [RFC1591]  Postel, J., "Domain Name System Structure and Delegation",
              RFC 1591, DOI 10.17487/RFC1591, March 1994,
              <https://www.rfc-editor.org/info/rfc1591>.

   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 2434,
              DOI 10.17487/RFC2434, October 1998,
              <https://www.rfc-editor.org/info/rfc2434>.

   [RFC2860]  Carpenter, B., Baker, F., and M. Roberts, "Memorandum of
              Understanding Concerning the Technical Work of the
              Internet Assigned Numbers Authority", RFC 2860,
              DOI 10.17487/RFC2860, June 2000,
              <https://www.rfc-editor.org/info/rfc2860>.

   [RFC2939]  Droms, R., "Procedures and IANA Guidelines for Definition
              of New DHCP Options and Message Types", BCP 43, RFC 2939,
              DOI 10.17487/RFC2939, September 2000,
              <https://www.rfc-editor.org/info/rfc2939>.

   [RFC3228]  Fenner, B., "IANA Considerations for IPv4 Internet Group
              Management Protocol (IGMP)", RFC 3228,
              DOI 10.17487/RFC3228, February 2002,
              <https://www.rfc-editor.org/info/rfc3228>.

   [RFC3575]  Aboba, B., "IANA Considerations for RADIUS (Remote
              Authentication Dial In User Service)", RFC 3575,
              DOI 10.17487/RFC3575, July 2003,
              <https://www.rfc-editor.org/info/rfc3575>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.




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   [RFC3692]  Narten, T., "Assigning Experimental and Testing Numbers
              Considered Useful", BCP 82, RFC 3692,
              DOI 10.17487/RFC3692, January 2004,
              <https://www.rfc-editor.org/info/rfc3692>.

   [RFC3748]  Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
              Levkowetz, Ed., "Extensible Authentication Protocol
              (EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004,
              <https://www.rfc-editor.org/info/rfc3748>.

   [RFC3864]  Klyne, G., Nottingham, M., and J. Mogul, "Registration
              Procedures for Message Header Fields", BCP 90, RFC 3864,
              DOI 10.17487/RFC3864, September 2004,
              <https://www.rfc-editor.org/info/rfc3864>.

   [RFC3942]  Volz, B., "Reclassifying Dynamic Host Configuration
              Protocol version 4 (DHCPv4) Options", RFC 3942,
              DOI 10.17487/RFC3942, November 2004,
              <https://www.rfc-editor.org/info/rfc3942>.

   [RFC4005]  Calhoun, P., Zorn, G., Spence, D., and D. Mitton,
              "Diameter Network Access Server Application", RFC 4005,
              DOI 10.17487/RFC4005, August 2005,
              <https://www.rfc-editor.org/info/rfc4005>.

   [RFC4025]  Richardson, M., "A Method for Storing IPsec Keying
              Material in DNS", RFC 4025, DOI 10.17487/RFC4025, March
              2005, <https://www.rfc-editor.org/info/rfc4025>.

   [RFC4044]  McCloghrie, K., "Fibre Channel Management MIB", RFC 4044,
              DOI 10.17487/RFC4044, May 2005,
              <https://www.rfc-editor.org/info/rfc4044>.

   [RFC4124]  Le Faucheur, F., Ed., "Protocol Extensions for Support of
              Diffserv-aware MPLS Traffic Engineering", RFC 4124,
              DOI 10.17487/RFC4124, June 2005,
              <https://www.rfc-editor.org/info/rfc4124>.

   [RFC4169]  Torvinen, V., Arkko, J., and M. Naslund, "Hypertext
              Transfer Protocol (HTTP) Digest Authentication Using
              Authentication and Key Agreement (AKA) Version-2",
              RFC 4169, DOI 10.17487/RFC4169, November 2005,
              <https://www.rfc-editor.org/info/rfc4169>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.



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   [RFC4283]  Patel, A., Leung, K., Khalil, M., Akhtar, H., and K.
              Chowdhury, "Mobile Node Identifier Option for Mobile IPv6
              (MIPv6)", RFC 4283, DOI 10.17487/RFC4283, November 2005,
              <https://www.rfc-editor.org/info/rfc4283>.

   [RFC4340]  Kohler, E., Handley, M., and S. Floyd, "Datagram
              Congestion Control Protocol (DCCP)", RFC 4340,
              DOI 10.17487/RFC4340, March 2006,
              <https://www.rfc-editor.org/info/rfc4340>.

   [RFC4422]  Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple
              Authentication and Security Layer (SASL)", RFC 4422,
              DOI 10.17487/RFC4422, June 2006,
              <https://www.rfc-editor.org/info/rfc4422>.

   [RFC4446]  Martini, L., "IANA Allocations for Pseudowire Edge to Edge
              Emulation (PWE3)", BCP 116, RFC 4446,
              DOI 10.17487/RFC4446, April 2006,
              <https://www.rfc-editor.org/info/rfc4446>.

   [RFC4520]  Zeilenga, K., "Internet Assigned Numbers Authority (IANA)
              Considerations for the Lightweight Directory Access
              Protocol (LDAP)", BCP 64, RFC 4520, DOI 10.17487/RFC4520,
              June 2006, <https://www.rfc-editor.org/info/rfc4520>.

   [RFC4589]  Schulzrinne, H. and H. Tschofenig, "Location Types
              Registry", RFC 4589, DOI 10.17487/RFC4589, July 2006,
              <https://www.rfc-editor.org/info/rfc4589>.

   [RFC4727]  Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4,
              ICMPv6, UDP, and TCP Headers", RFC 4727,
              DOI 10.17487/RFC4727, November 2006,
              <https://www.rfc-editor.org/info/rfc4727>.

   [RFC5237]  Arkko, J. and S. Bradner, "IANA Allocation Guidelines for
              the Protocol Field", BCP 37, RFC 5237,
              DOI 10.17487/RFC5237, February 2008,
              <https://www.rfc-editor.org/info/rfc5237>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

   [RFC5378]  Bradner, S., Ed. and J. Contreras, Ed., "Rights
              Contributors Provide to the IETF Trust", BCP 78, RFC 5378,
              DOI 10.17487/RFC5378, November 2008,
              <https://www.rfc-editor.org/info/rfc5378>.



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   [RFC5742]  Alvestrand, H. and R. Housley, "IESG Procedures for
              Handling of Independent and IRTF Stream Submissions",
              BCP 92, RFC 5742, DOI 10.17487/RFC5742, December 2009,
              <https://www.rfc-editor.org/info/rfc5742>.

   [RFC5795]  Sandlund, K., Pelletier, G., and L. Jonsson, "The RObust
              Header Compression (ROHC) Framework", RFC 5795,
              DOI 10.17487/RFC5795, March 2010,
              <https://www.rfc-editor.org/info/rfc5795>.

   [RFC5971]  Schulzrinne, H. and R. Hancock, "GIST: General Internet
              Signalling Transport", RFC 5971, DOI 10.17487/RFC5971,
              October 2010, <https://www.rfc-editor.org/info/rfc5971>.

   [RFC6014]  Hoffman, P., "Cryptographic Algorithm Identifier
              Allocation for DNSSEC", RFC 6014, DOI 10.17487/RFC6014,
              November 2010, <https://www.rfc-editor.org/info/rfc6014>.

   [RFC6195]  Eastlake 3rd, D., "Domain Name System (DNS) IANA
              Considerations", RFC 6195, DOI 10.17487/RFC6195, March
              2011, <https://www.rfc-editor.org/info/rfc6195>.

   [RFC6230]  Boulton, C., Melanchuk, T., and S. McGlashan, "Media
              Control Channel Framework", RFC 6230,
              DOI 10.17487/RFC6230, May 2011,
              <https://www.rfc-editor.org/info/rfc6230>.

   [RFC6275]  Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
              Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
              2011, <https://www.rfc-editor.org/info/rfc6275>.

   [RFC6335]  Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
              Cheshire, "Internet Assigned Numbers Authority (IANA)
              Procedures for the Management of the Service Name and
              Transport Protocol Port Number Registry", BCP 165,
              RFC 6335, DOI 10.17487/RFC6335, August 2011,
              <https://www.rfc-editor.org/info/rfc6335>.

   [RFC6698]  Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
              of Named Entities (DANE) Transport Layer Security (TLS)
              Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August
              2012, <https://www.rfc-editor.org/info/rfc6698>.

   [RFC6709]  Carpenter, B., Aboba, B., Ed., and S. Cheshire, "Design
              Considerations for Protocol Extensions", RFC 6709,
              DOI 10.17487/RFC6709, September 2012,
              <https://www.rfc-editor.org/info/rfc6709>.




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   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <https://www.rfc-editor.org/info/rfc6838>.

   [RFC6929]  DeKok, A. and A. Lior, "Remote Authentication Dial In User
              Service (RADIUS) Protocol Extensions", RFC 6929,
              DOI 10.17487/RFC6929, April 2013,
              <https://www.rfc-editor.org/info/rfc6929>.

   [RFC6994]  Touch, J., "Shared Use of Experimental TCP Options",
              RFC 6994, DOI 10.17487/RFC6994, August 2013,
              <https://www.rfc-editor.org/info/rfc6994>.

   [RFC7120]  Cotton, M., "Early IANA Allocation of Standards Track Code
              Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January
              2014, <https://www.rfc-editor.org/info/rfc7120>.

   [RFC7499]  Perez-Mendez, A., Ed., Marin-Lopez, R., Pereniguez-Garcia,
              F., Lopez-Millan, G., Lopez, D., and A. DeKok, "Support of
              Fragmentation of RADIUS Packets", RFC 7499,
              DOI 10.17487/RFC7499, April 2015,
              <https://www.rfc-editor.org/info/rfc7499>.

   [RFC7564]  Saint-Andre, P. and M. Blanchet, "PRECIS Framework:
              Preparation, Enforcement, and Comparison of
              Internationalized Strings in Application Protocols",
              RFC 7564, DOI 10.17487/RFC7564, May 2015,
              <https://www.rfc-editor.org/info/rfc7564>.

   [RFC7595]  Thaler, D., Ed., Hansen, T., and T. Hardie, "Guidelines
              and Registration Procedures for URI Schemes", BCP 35,
              RFC 7595, DOI 10.17487/RFC7595, June 2015,
              <https://www.rfc-editor.org/info/rfc7595>.

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>.

   [RFC8141]  Saint-Andre, P. and J. Klensin, "Uniform Resource Names
              (URNs)", RFC 8141, DOI 10.17487/RFC8141, April 2017,
              <https://www.rfc-editor.org/info/rfc8141>.

   [RFC8392]  Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
              "CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
              May 2018, <https://www.rfc-editor.org/info/rfc8392>.



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   [RFC8415]  Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
              Richardson, M., Jiang, S., Lemon, T., and T. Winters,
              "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
              RFC 8415, DOI 10.17487/RFC8415, November 2018,
              <https://www.rfc-editor.org/info/rfc8415>.

   [RFC8447]  Salowey, J. and S. Turner, "IANA Registry Updates for TLS
              and DTLS", RFC 8447, DOI 10.17487/RFC8447, August 2018,
              <https://www.rfc-editor.org/info/rfc8447>.

   [RFC8615]  Nottingham, M., "Well-Known Uniform Resource Identifiers
              (URIs)", RFC 8615, DOI 10.17487/RFC8615, May 2019,
              <https://www.rfc-editor.org/info/rfc8615>.

   [RFC8726]  Farrel, A., "How Requests for IANA Action Will Be Handled
              on the Independent Stream", RFC 8726,
              DOI 10.17487/RFC8726, November 2020,
              <https://www.rfc-editor.org/info/rfc8726>.

   [RFC9000]  Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,
              <https://www.rfc-editor.org/info/rfc9000>.

   [RFC9012]  Patel, K., Van de Velde, G., Sangli, S., and J. Scudder,
              "The BGP Tunnel Encapsulation Attribute", RFC 9012,
              DOI 10.17487/RFC9012, April 2021,
              <https://www.rfc-editor.org/info/rfc9012>.

   [RFC9454]  Fox, M., Lindem, A., and A. Retana, "Update to OSPF
              Terminology", RFC 9454, DOI 10.17487/RFC9454, August 2023,
              <https://www.rfc-editor.org/info/rfc9454>.

   [RFC9516]  Mirsky, G., Meng, W., Ao, T., Khasnabish, B., Leung, K.,
              and G. Mishra, "Active Operations, Administration, and
              Maintenance (OAM) for Service Function Chaining (SFC)",
              RFC 9516, DOI 10.17487/RFC9516, November 2023,
              <https://www.rfc-editor.org/info/rfc9516>.

   [RFC9546]  Mirsky, G., Chen, M., and B. Varga, "Operations,
              Administration, and Maintenance (OAM) for Deterministic
              Networking (DetNet) with the MPLS Data Plane", RFC 9546,
              DOI 10.17487/RFC9546, February 2024,
              <https://www.rfc-editor.org/info/rfc9546>.







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   [RFC9594]  Palombini, F. and M. Tiloca, "Key Provisioning for Group
              Communication Using Authentication and Authorization for
              Constrained Environments (ACE)", RFC 9594,
              DOI 10.17487/RFC9594, September 2024,
              <https://www.rfc-editor.org/info/rfc9594>.

   [I-D.ietf-netmod-rfc8407bis]
              Bierman, A., Boucadair, M., and Q. Wu, "Guidelines for
              Authors and Reviewers of Documents Containing YANG Data
              Models", Work in Progress, Internet-Draft, draft-ietf-
              netmod-rfc8407bis-28, 5 June 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
              rfc8407bis-28>.

   [I-D.ietf-tls-rfc8447bis]
              Salowey, J. A. and S. Turner, "IANA Registry Updates for
              TLS and DTLS", Work in Progress, Internet-Draft, draft-
              ietf-tls-rfc8447bis-15, 21 July 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-tls-
              rfc8447bis-15>.

   [I-D.ietf-dnsop-rfc8624-bis]
              Hardaker, W. and W. Kumari, "DNSSEC Cryptographic
              Algorithm Recommendation Update Process", Work in
              Progress, Internet-Draft, draft-ietf-dnsop-rfc8624-bis-13,
              4 June 2025, <https://datatracker.ietf.org/doc/html/draft-
              ietf-dnsop-rfc8624-bis-13>.

Appendix A.  Changes Relative to Earlier Editions of BCP 26

A.1.  2025: Changes in This Document Relative to RFC 8126

   %% NOTE TO IANABIS: Much more will be detailed here as the document
   progresses. %%

   Significant additions:

   *  Added and defined preferred registry organization terms ("registry
      group," "registry," and "subregistry").

   *  Much more information about registry groups in many places.

   *  Proposed new and revised registration procedures to IANABIS.
      Included questions at the top of the section.

   *  Added registry design and IANA Considerations language
      recommendations.




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   *  Added information about adding notes to registries.

   *  Added "bis" request (summarize instructions to IANA when
      replicating an existing section).

   Clarifications and such:

   *  Added mailing list creation advice.

   *  Noted that IANA will create change controller fields for some
      registries.

A.2.  2016: Changes in This Document Relative to RFC 5226

   Significant additions:

   *  Removed RFC 2119 key words, boilerplate, and reference, preferring
      plain English -- this is not a protocol specification.

   *  Added Section 1.1, Keep IANA Considerations for IANA

   *  Added Section 1.2, For Updated Information

   *  Added Section 2.1, Organization of Registries

   *  Added best practice for selecting an appropriate policy into
      Section 4.

   *  Added Section 4.13, Using Multiple Policies in Combination

   *  Added Section 2.3, Specifying Change Control for a Registry

   *  Added Section 3.4, Early Allocations

   *  Moved each well-known policy into a separate subsection of
      Section 4.

   *  Added Section 5.4, Expert Reviews and the Document Lifecycle

   *  Added Section 7, Documentation References in IANA Registries

   *  Added Section 8, What to Do in "bis" Documents

   *  Added Section 9.5, Contact Person vs Assignee or Owner

   *  Added Section 9.6, Closing or Obsoleting a Registry/Registrations

   Clarifications and such:



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   *  Some reorganization -- moved text around for clarity and easier
      reading.

   *  Made clarifications about identification of IANA registries and
      use of URLs for them.

   *  Clarified the distinction between "Unassigned" and "Reserved".

   *  Made some clarifications in "Expert Review" about instructions to
      the designated expert.

   *  Made some clarifications in "Specification Required" about how to
      declare this policy.

   *  Assorted minor clarifications and editorial changes throughout.

A.3.  2008: Changes in RFC 5226 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) and 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
      RFCs".

   *  "Specification Required" now implies use of a designated expert to
      evaluate specs for sufficient clarity.

   *  Added a section describing provisional registrations.

   *  Significantly changed the wording in the "Designated Experts"
      section.  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 case.




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   *  Changed wording to remove any special appeals path.  The normal
      RFC 2026 appeals path is used.

   *  Added a section about reclaiming unused values.

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

   *  Added a section indicating that mailing lists used to evaluate
      possible assignments (such as by a designated expert) are subject
      to normal IETF rules.

Appendix B.  Acknowledgments

B.1.  Acknowledgments for This Document (2025)

   Barry Leiba, Michelle Cotton, and Thomas Narten edited the previous
   edition of this document (RFC 8126).  Most of the text from that
   document remains in this edition.

   Thanks to Carsten Bormann, Marco Tiloca, and John Klensin for their
   work in defining the "With Expert Review" and two-tiered registration
   models.

B.2.  Acknowledgments for the Third Edition (2017)

   Thomas Narten and Harald Tveit Alvestrand edited the two earlier
   editions of this document (RFCs 2434 and 5226), and Thomas continues
   his role in this third edition.  Much of the text from RFC 5226
   remains in this edition.

   Thank you to Amanda Baber and Pearl Liang for their multiple reviews
   and suggestions for making this document as thorough as possible.

   This document has benefited from thorough review and comments by many
   people, including Benoit Claise, Alissa Cooper, Adrian Farrel,
   Stephen Farrell, Tony Hansen, John Klensin, Kathleen Moriarty, Mark
   Nottingham, Pete Resnick, and Joe Touch.

   Special thanks to Mark Nottingham for reorganizing some of the text
   for better organization and readability, to Tony Hansen for acting as
   document shepherd, and to Brian Haberman and Terry Manderson for
   acting as sponsoring ADs.

B.3.  Acknowledgments from the Second Edition (2008)

   The original acknowledgments section in RFC 5226 was:





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

B.4.  Acknowledgments from the First Edition (1998)

   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 RFC 4288.

Authors' Addresses

   Amanda Baber (editor)
   Internet Assigned Numbers Authority
   PTI/ICANN
   12025 Waterfront Drive
   Los Angeles,  90094
   United States of America
   Email: amanda.baber@iana.org


   Sabrina Tanamal (editor)
   Internet Assigned Numbers Authority
   PTI/ICANN
   12025 Waterfront Drive
   Los Angeles,  90094
   United States of America
   Email: sabrina.tanamal@iana.org
















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