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RDAP Extensions
draft-newton-regext-rdap-extensions-01

Document Type Active Internet-Draft (candidate for regext WG)
Authors Andy Newton , Jasdip Singh , Tom Harrison
Last updated 2024-02-05 (Latest revision 2023-08-31)
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draft-newton-regext-rdap-extensions-01
Registration Protocols Extensions (regext)                     A. Newton
Internet-Draft                                                     ICANN
Updates: 7480, 9082, 9083 (if approved)                         J. Singh
Intended status: Standards Track                                    ARIN
Expires: 3 March 2024                                        T. Harrison
                                                                   APNIC
                                                          31 August 2023

                            RDAP Extensions
                 draft-newton-regext-rdap-extensions-01

Abstract

   This document describes and clarifies the usage of extensions in
   RDAP.

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 3 March 2024.

Copyright Notice

   Copyright (c) 2023 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.

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Table of Contents

   1.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  The RDAP Extension Identifier . . . . . . . . . . . . . . . .   2
   3.  Usage in Queries  . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Usage in JSON . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Child JSON Values . . . . . . . . . . . . . . . . . . . .   5
     4.2.  Bare Extension Identifiers  . . . . . . . . . . . . . . .   6
   5.  Camel Casing  . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Two Classes of Extensions . . . . . . . . . . . . . . . . . .   7
   7.  Profile and Marker Extensions . . . . . . . . . . . . . . . .   7
   8.  Extension Versioning  . . . . . . . . . . . . . . . . . . . .   8
     8.1.  Backwards-Compatible Changes  . . . . . . . . . . . . . .   8
     8.2.  Backwards-Incompatible Changes  . . . . . . . . . . . . .   8
   9.  Extension Definitions . . . . . . . . . . . . . . . . . . . .   9
   10. Existing Extension Registrations  . . . . . . . . . . . . . .   9
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   12. Normative References  . . . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Background

   The Registration Data Access Protocol (RDAP) defines a uniform means
   to access data from Internet operations registries, specifically
   Domain Name Registries (DNRs) and Internet Number Registries (INRs).
   The queries for DNRs and INRs are defined in [RFC9082] and the
   responses for DNRs and INRs are defined in [RFC9083].

   RDAP contains a means to define extensions for queries not found in
   [RFC9082] and responses not found in [RFC9083].  RDAP extensions are
   also described in [RFC7480].  This document uniformly describes RDAP
   extensions, clarifies their usage, and defines additional semantics
   that were previously undefined.

2.  The RDAP Extension Identifier

   Section 6 of [RFC7480] describes the identifier used to signify RDAP
   extensions and the IANA registry into which RDAP extensions are to be
   registered.

   In brief, RDAP extensions identifiers start with an alphabetic
   character and may contain alphanumeric characters and "_"
   (underscore) characters.  This formulation was explicitly chosen to
   allow compatibility with variable names in programming languages and
   transliteration with XML.

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   When in use in RDAP, extension identifiers are prepended to URL path
   segments, URL query parameters, and JSON object member names (herein
   further referred to as "JSON names").  In all cases, the extension
   identifier acts as a namespace preventing collisions between
   extension elements.

   Additionally, implementers and operators can use the extension
   identifiers to find an extensions definition (via the IANA registry).

   RDAP extension identifiers have no explicit structure and are opaque
   in that no inner-meaning can be "seen" in them.  This document
   restricts the syntax of RDAP extension identifiers from containing
   two consecutive "_" (underscore) characters and reserves their use
   for the future definition of structure (such as to define a
   versioning scheme).  That is, RDAP extensions MUST NOT define an
   identifier with two consecutive underscore characters ("__") unless
   explicitly adhering to an RFC describing such usage.

   RDAP extensions MUST NOT define an extension identifier that when
   prepended to an underscore character may collide with an existing
   extension identifier.  For example, if there were a pre-existing
   identifier of "foo_bar", another extension could not define the
   identifier "foo".  Likewise, if there were a pre-existing identifier
   of "foo_bar", another extension could not define the identifier
   "foo_bar_buzz".  However, an extension could define "foo" if "foobar"
   pre-existed and vice versa.

   For this reason, usage of an underscore character in RDAP extension
   identifiers is NOT RECOMMENDED.  Implementers should be aware that
   many existing extension identifiers do contain underscore characters.

3.  Usage in Queries

   Section 5 of [RFC9082] describes the use of extension identifiers in
   formulating URIs to query RDAP servers.  The extension identifiers
   are to be prepended to the path segments they use.  For example, if
   an extension uses the identifier foobar, then the path segments used
   in that extension are prepended with foobar_. If the foobar extension
   defines paths fizz and fazz, the URIs for this extension might take
   the following form:

   https://base.example/foobar_fizz
   https://base.example/foobar_fazz

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   Although [RFC9082] describes the use of URI query strings, it does
   not define their use with extensions.  [RFC7480] instructs servers to
   ignore unknown query parameters.  Therefore, the use of query
   parameters, prefixed or not with an extension identifier, is
   undefined as defined in [RFC9082] and [RFC7480].

   Despite this, there are several extensions that do specify query
   parameters.  This document updates [RFC9082] with regard to the use
   of RDAP extension identifiers in URL query parameters.

   When an RDAP extension defines query parameters to be used with a URL
   path that is not defined by that RDAP extension, those query
   parameter names SHOULD be constructed in the same manner as URL path
   segments (that is, extensions ID + '_' + parameter name).  See
   section Section 6 regarding when usage of an extension identifier is
   required.

   When an RDAP extension defines query parameters to be used with a URL
   path defined by that RDAP extension, prefixing of query parameters is
   not required.

4.  Usage in JSON

   Section 2 of [RFC9083] describes the use of extension identifiers in
   the JSON returned by RDAP servers.  Just as in URIs, the extension
   identifier is prepended to JSON names to create a namespace so that
   the JSON name from one extension will not collide with the JSON name
   of another extension.  And just as with URIs, clients are to ignore
   unknown JSON names.

   The example given in [RFC9083] is as follows:

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   {
     "handle" : "ABC123",
     "lunarNIC_beforeOneSmallStep" : "TRUE THAT!",
     "remarks" :
     [
       {
         "description" :
         [
           "She sells sea shells down by the sea shore.",
           "Originally written by Terry Sullivan."
         ]
       }
     ],
     "lunarNIC_harshMistressNotes" :
     [
       "In space,",
       "nobody can hear you scream."
     ]
   }

   In this example, the extension identified by lunarNIC is prepended to
   the names of both a JSON string and a JSON array.

4.1.  Child JSON Values

   Prefixing of the extension identifier is not required of children of
   a prefixed JSON object defined by an RDAP extension.

   The following example shows this use with a JSON object.

   {
     "handle" : "ABC123",
     "remarks" :
     [
       {
         "description" :
         [
           "She sells sea shells down by the sea shore.",
           "Originally written by Terry Sullivan."
         ]
       }
     ],
     "lunarNIC_author" :
     {
       "firstInitial": "J",
       "lastName": "Heinlein"
     }
   }

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   Here the JSON name "lunarNic_author" will separate the JSON from
   other extensions that may have an "author" structure.  But the JSON
   contained within "lunarNIC_author" need not be prepended as the
   extension collision is avoided by "lunarNIC_author".

4.2.  Bare Extension Identifiers

   Some RDAP extensions define only one JSON value and do not prefix it
   with their RDAP extension identifier instead using the extension
   identifier as the JSON name for that JSON value.  That is, the
   extension identifier is used "bare" and not appended with an
   underscore character and subsequent names.

   Consider the example in Section 4.1.  Using the bare extension
   identifier pattern, that example could be written as:

   {
     "handle" : "ABC123",
     "remarks" :
     [
       {
         "description" :
         [
           "She sells sea shells down by the sea shore.",
           "Originally written by Terry Sullivan."
         ]
       }
     ],
     "lunarNIC" :
     {
       "firstInitial": "J",
       "lastName": "Heinlein"
     }
   }

   Usage of a bare extension identifier contravenes the guidance in
   [RFC9083].  This document updates [RFC9083] to explicitly allow this
   pattern.

5.  Camel Casing

   The styling convention used in [RFC9083] for JSON names is often
   called "camel casing", in reference to the hump of a camel.  In this
   style, the first letter of every word, except the first word,
   composing a name is capitalized.  This convention was adopted to
   visually separate the namespace from the name, with an underscore
   between them.

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   Though there is no explicit guidance to use camel case names,
   extensions would be wise to continue the style.

6.  Two Classes of Extensions

   Though all RDAP extensions are to be registered in the IANA RDAP
   extensions registry, there is an implicit two-class system of
   extensions that comes from the inherit ownership of the RDAP
   specifications by the IETF: extensions created by the IETF and
   extensions not created by the IETF.

   In the perspective of how extensions identifiers are used as
   namespace separators, extensions created by the IETF are not required
   to be prefixed with an extension identifier as the IETF can
   coordinate its own activities to avoid name collisions.  In practice,
   most extensions owned by the IETF do use extension identifiers.

   RDAP extensions not defined by the IETF MUST use the extension
   identifier as a prefix in accordance with this document, [RFC7480],
   [RFC9082], and [RFC9083].  And RDAP extensions defined by the IETF
   SHOULD use the extension identifier as a prefix or as a bare
   extension identifier (see Section 4.2) IETF defined RDAP extensions
   that do not follow this guidance MUST describe the necessity to do
   so.

7.  Profile and Marker Extensions

   Extensions are not required to extend the JSON or URL components of
   RDAP.

   While the RDAP extension mechanism was created to extend RDAP queries
   and/or responses, extensions can also be used to signal server policy
   (for example, specifying the conditions of use for existing response
   structures).  Extensions that are primarily about signalling server
   policy are often called "profiles".

   Some extensions exist to denote the usage of values placed into an
   IANA registry, such as the IANA RDAP registries, or the usage of
   extensions to technologies used by RDAP such as extended vCard/jCard
   properties.  Such extensions exist to "mark" these usages and are
   often called "marker" extensions.

   Regardless of the category of these extensions, their usage may also
   leverage the appearance of their identifiers in the rdapConformance
   array.  Clients may use the /help query as defined in [RFC9082] to
   discover the extensions available.  This document updates the
   guidance of [RFC9083] with respect to /help queries: servers SHOULD
   place an rdapConformance array in the response to a /help query.

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8.  Extension Versioning

   As stated in Section 2, RDAP extensions are opaque and they posses no
   explicit version despite the fact that some extension identifiers
   include trailing numbers.  That is, RDAP extensions without an
   explicitly defined versioning scheme are opaquely versioned.

   For example, fizzbuzz_1 may be the successor to fizzbuzz_0, but it
   may also be an extension for a completely separate purpose.  Only
   consultation of the definition of fizzbuzz_1 will determine its
   relationship with fizzbuzz_0.  Additionally, fizzbuzz_99 may be the
   predecessor of fizzbuzz_0.

   If a future RFC defines a versioning scheme (such as using the
   mechanims defined in section Section 2), an RDAP extension definition
   MUST explicitly denote this compliance.

8.1.  Backwards-Compatible Changes

   If an RDAP extension author wants to publish a new version of an
   extension that is backwards-compatible with the previous version,
   then one option is for the new version of the extension to define a
   new identifier, as well as requiring that both the previous
   identifier and the new identifier be included in the
   "rdapConformance" array of responses.  That way, clients relying on
   the previous version of the extension will continue to function as
   intended, while clients wanting to make use of the newer version of
   the extension can check for the new identifier in the response.

   This approach can be used for an arbitrary number of new backwards-
   compatible versions of a given extension.  For an extension with a
   large number of backwards-compatible successor versions, this may
   lead to a large number of identifiers being included in responses.
   An extension author may consider excluding older identifiers from the
   set required by new successor versions, based on data about client
   use/support or similar.

8.2.  Backwards-Incompatible Changes

   With the current extension model, an extension with a backwards-
   incompatible change is indistinguishable from a new, unrelated
   extension.  Implementors of such changes should consider the
   following:

   *  whether the new version of the extension can be provided alongside
      the old version of the extension, so that a service can simply
      support both during a transition period;

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   *  whether some sort of client signalling should be supported, so
      that clients can opt for the old or new version of the extension
      in responses that they receive (see
      [I-D.newton-regext-rdap-x-media-type] for an example of how this
      might work); and
   *  whether the extension itself should define how versioning is
      handled within the extension documentation.

9.  Extension Definitions

   Extensions must be documented in an RFC or in some other permanent
   and readily available reference, in sufficient detail that
   interoperability between independent implementations is possible.

   Though RDAP gives each extension its own namespace, the definition of
   an extension may re-use definitions found in the base RDAP
   specification or in any other properly registered extension.

   [RFC9083] notes that the extension identifiers provide a "hint" to
   the client as to how to interpret the response.  This wording does
   not intentionally restrict the extension to defining only JSON values
   within the extensions namespace.  Therefore, an extension may define
   the use of its own JSON values together with the use of JSON values
   from other extensions or RDAP specifications.  As with the ICANN
   profile or RIR profile extensions, the extension may simply signal
   policy applied to already defined RDAP structures.

10.  Existing Extension Registrations

   The following extensions have been registered with IANA, but do not
   comply with the requirements set out in the base specifications, as
   clarified by this document:

   *  Extension identifier: fred

      -  RDAP conformance value: fred_version_0
      -  Field/path prefix: fred

   *  Extension identifier: artRecord

      -  RDAP conformance value: artRecord_level_0
      -  Field/path prefix: artRecord

   *  Extension identifier: platformNS

      -  RDAP conformance value: platformNS_level_0
      -  Field/path prefix: platformNS

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   *  Extension identifier: regType

      -  RDAP conformance value: regType_level_0
      -  Field/path prefix: regType

   Client authors should be aware that responses that make use of these
   extensions may require special handling on the part of the client.
   Also, while these extensions will be retained in the registry, future
   extensions that are similarly noncompliant will not be registered.

   To avoid any confusion with the operation of the existing entries, an
   extension registration that attempts to use one of the RDAP
   conformance values given in this section as an extension identifier
   (and so as an RDAP conformance value also) will be rejected.

11.  Acknowledgements

   The following individuals have provided feedback and contributions to
   the content and direction of this document: James Gould, Daniel
   Keathley, and Ties de Kock.

12.  Normative References

   [I-D.newton-regext-rdap-x-media-type]
              Newton, A. and J. Singh, "An RDAP With Extensions Media
              Type", Work in Progress, Internet-Draft, draft-newton-
              regext-rdap-x-media-type-01, 29 August 2023,
              <https://datatracker.ietf.org/doc/html/draft-newton-
              regext-rdap-x-media-type-01>.

   [RFC7480]  Newton, A., Ellacott, B., and N. Kong, "HTTP Usage in the
              Registration Data Access Protocol (RDAP)", STD 95,
              RFC 7480, DOI 10.17487/RFC7480, March 2015,
              <https://www.rfc-editor.org/info/rfc7480>.

   [RFC9082]  Hollenbeck, S. and A. Newton, "Registration Data Access
              Protocol (RDAP) Query Format", STD 95, RFC 9082,
              DOI 10.17487/RFC9082, June 2021,
              <https://www.rfc-editor.org/info/rfc9082>.

   [RFC9083]  Hollenbeck, S. and A. Newton, "JSON Responses for the
              Registration Data Access Protocol (RDAP)", STD 95,
              RFC 9083, DOI 10.17487/RFC9083, June 2021,
              <https://www.rfc-editor.org/info/rfc9083>.

Authors' Addresses

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   Andy Newton
   ICANN
   Email: andy@hxr.us

   Jasdip Singh
   ARIN
   Email: jasdips@arin.net

   Tom Harrison
   APNIC
   Email: tomh@apnic.net

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