CoRE Target Attributes Registry
draft-ietf-core-target-attr-03

CoRE Working group                                            C. Bormann
Internet-Draft                                    Universität Bremen TZI
Updates: 9176 (if approved)                                 3 March 2023
Intended status: Informational                                          
Expires: 4 September 2023

                    CoRE Target Attributes Registry
                     draft-ietf-core-target-attr-03

Abstract

   The Constrained RESTful Environments (CoRE) specifications apply Web
   technologies to constrained environments.  One important such
   technology is Web Linking (RFC 8288), which CoRE uses as the basis
   for a number of discovery protocols, such as the Link Format (RFC
   6690) in CoAP's Resource Discovery Protocol (Section 7.2 of RFC7252)
   and the Resource Directory (RFC 9176).

   Web Links can have target attributes, the names of which are not
   generally coordinated by the Web Linking specification (Section 2.2
   of RFC 8288).  This short note introduces an IANA registry for
   coordinating names of target attributes when used in Constrained
   RESTful Environments.  It updates the RD Parameters Registry of RFC
   9176 to coordinate with this registry.

About This Document

   This note is to be removed before publishing as an RFC.

   Status information for this document may be found at
   https://datatracker.ietf.org/doc/draft-ietf-core-target-attr/.

   Discussion of this document takes place on the core Working Group
   mailing list (mailto:core@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/core/.  Subscribe at
   https://www.ietf.org/mailman/listinfo/core/.

   Source for this draft and an issue tracker can be found at
   https://github.com/core-wg/core-target-attr.

Status of This Memo

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

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Instructions for the Designated Expert  . . . . . . . . .   4
     2.2.  Structure of Entries  . . . . . . . . . . . . . . . . . .   4
     2.3.  Initial Entries . . . . . . . . . . . . . . . . . . . . .   5
   3.  Security considerations . . . . . . . . . . . . . . . . . . .   6
   4.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     4.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   8
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .   8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

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1.  Introduction

   The Constrained RESTful Environments (CoRE) specifications apply Web
   technologies to constrained environments.  One important such
   technology is Web Linking [RFC8288], which CoRE uses as the basis for
   a number of discovery protocols, such as the Link Format [RFC6690] in
   CoAP's Resource Discovery Protocol (Section 7.2 of [RFC7252]) and the
   Resource Directory [RFC9176].

   Web Links can have target attributes.  The original Web Linking
   specification (Section 3 of [RFC5988]) did not attempt to coordinate
   names of target attributes except for providing common target
   attributes for use in the Link HTTP header.  The current revision of
   that specification clarifies (Section 2.2 of [RFC8288]):

   |  This specification does not attempt to coordinate the name of
   |  target attributes, their cardinality, or use.  Those creating and
   |  maintaining serialisations SHOULD coordinate their target
   |  attributes to avoid conflicts in semantics or syntax and MAY
   |  define their own registries of target attributes.

   This short note introduces an IANA registry for coordinating names of
   target attributes when used in Constrained RESTful Environments, with
   specific instructions for the designated expert for this registry
   (Section 2.1).

   With a registry now available, registration of target attributes is
   strongly encouraged.  The incentive is that an unregistered attribute
   name might be registered with a different meaning at any time.

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  IANA Considerations

   This specification defines a new Target Attributes sub-registry in
   the CoRE Parameters registry [IANA.core-parameters], with the policy
   "Expert Review" (Section 4.5 of [BCP26]).

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2.1.  Instructions for the Designated Expert

   The expert is instructed to be frugal in the allocation of very short
   target attribute names, keeping them in reserve for applications that
   are likely to enjoy wide use and can make good use of their
   shortness.

   The expert is also instructed to direct the registrant to provide a
   specification (Section 4.6 of [BCP26]), but can make exceptions, for
   instance when a specification is not available at the time of
   registration but is likely forthcoming.

   Any questions or issues that might interest a wider audience might be
   raised by the expert on the core-parameters@ietf.org mailing list for
   a time-limited discussion.  This might include security
   considerations, or opportunities for orchestration, e.g., when
   different names with similar intent are being or could be registered.

   If the expert becomes aware of target attributes that are deployed
   and in use, they may also initiate a registration on their own if
   they deem such a registration can avert potential future collisions.

2.2.  Structure of Entries

   Each entry in the registry must include:

   Attribute Name:
      a lower case ASCII [STD80] string that starts with a letter and
      can contain digits and hyphen-minus characters afterward
      ([a-z][-a-z0-9]*).  (Note that [RFC8288] requires target attribute
      names to be interpreted in a case-insensitive way; the restriction
      to lower case here ensures that they are registered in a
      predictable form).

   Brief description:
      a brief description

   Change Controller:
      (see Section 2.3 of [BCP26])

   Reference:
      a reference document that provides a description of the target
      attribute, including the semantics for when the target attribute
      appears more than once in a link.

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2.3.  Initial Entries

   Initial entries in this sub-registry are as listed in Table 1:

   +===========+=========================+============+===============+
   | Attribute | Brief description       | Change     | Reference     |
   | Name      |                         | Controller |               |
   +===========+=========================+============+===============+
   | href      | reserved (not useful as | IESG       | [RFC6690]     |
   |           | target attribute name)  |            |               |
   +-----------+-------------------------+------------+---------------+
   | anchor    | reserved (not useful as | IESG       | [RFC6690]     |
   |           | target attribute name)  |            |               |
   +-----------+-------------------------+------------+---------------+
   | rel       | reserved (not useful as | IESG       | [RFC6690]     |
   |           | target attribute name)  |            |               |
   +-----------+-------------------------+------------+---------------+
   | rev       | reserved (not useful as | IESG       | [RFC6690]     |
   |           | target attribute name)  |            |               |
   +-----------+-------------------------+------------+---------------+
   | hreflang  | (Web Linking)           | IESG       | [RFC8288]     |
   +-----------+-------------------------+------------+---------------+
   | media     | (Web Linking)           | IESG       | [RFC8288]     |
   +-----------+-------------------------+------------+---------------+
   | title     | (Web Linking)           | IESG       | [RFC8288]     |
   +-----------+-------------------------+------------+---------------+
   | type      | (Web Linking)           | IESG       | [RFC8288]     |
   +-----------+-------------------------+------------+---------------+
   | rt        | resource type           | IESG       | Section 3.1   |
   |           |                         |            | of [RFC6690]  |
   +-----------+-------------------------+------------+---------------+
   | if        | interface description   | IESG       | Section 3.2   |
   |           |                         |            | of [RFC6690]  |
   +-----------+-------------------------+------------+---------------+
   | sz        | maximum size estimate   | IESG       | Section 3.3   |
   |           |                         |            | of [RFC6690]  |
   +-----------+-------------------------+------------+---------------+
   | ct        | Content-Format hint     | IESG       | Section 7.2.1 |
   |           |                         |            | of [RFC7252]  |
   +-----------+-------------------------+------------+---------------+
   | obs       | observable resource     | IESG       | Section 6 of  |
   |           |                         |            | [RFC7641]     |
   +-----------+-------------------------+------------+---------------+
   | hct       | HTTP-CoAP URI mapping   | IESG       | Section 5.5   |
   |           | template                |            | of [RFC8075]  |
   +-----------+-------------------------+------------+---------------+
   | osc       | hint: resource only     | IESG       | Section 9 of  |
   |           | accessible using OSCORE |            | [RFC8613]     |

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   +-----------+-------------------------+------------+---------------+
   | ep        | Endpoint Name (with     | IESG       | Section 9.3   |
   |           | rt="core.rd-ep")        |            | of [RFC9176]  |
   +-----------+-------------------------+------------+---------------+
   | d         | Sector (with            | IESG       | Section 9.3   |
   |           | rt="core.rd-ep")        |            | of [RFC9176]  |
   +-----------+-------------------------+------------+---------------+
   | base      | Registration Base URI   | IESG       | Section 9.3   |
   |           | (with rt="core.rd-ep")  |            | of [RFC9176]  |
   +-----------+-------------------------+------------+---------------+
   | et        | Endpoint Type (with     | IESG       | Section 9.3   |
   |           | rt="core.rd-ep")        |            | of [RFC9176]  |
   +-----------+-------------------------+------------+---------------+

        Table 1: Initial Entries in the Target Attributes Registry

   A number of names are reserved as they are used for parameters in
   links other than target attributes, this includes a further set that
   is predefined in [RFC8288].

   Section 9.3 of [RFC9176] defines the RD Parameters sub-registry.  The
   present document updates this registry with a note that all entries
   with the "A" flag set MUST also get registered over here.

3.  Security considerations

   The security considerations of [RFC8288] apply, as do those of the
   discovery specifications [RFC6690], [RFC7252], and [RFC9176].

4.  References

4.1.  Normative References

   [BCP26]    Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/rfc/rfc8126>.

   [IANA.core-parameters]
              IANA, "Constrained RESTful Environments (CoRE)
              Parameters",
              <https://www.iana.org/assignments/core-parameters>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/rfc/rfc2119>.

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   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

   [RFC8288]  Nottingham, M., "Web Linking", RFC 8288,
              DOI 10.17487/RFC8288, October 2017,
              <https://www.rfc-editor.org/rfc/rfc8288>.

   [STD80]    Cerf, V., "ASCII format for network interchange", STD 80,
              RFC 20, DOI 10.17487/RFC0020, October 1969,
              <https://www.rfc-editor.org/rfc/rfc20>.

4.2.  Informative References

   [RFC5988]  Nottingham, M., "Web Linking", RFC 5988,
              DOI 10.17487/RFC5988, October 2010,
              <https://www.rfc-editor.org/rfc/rfc5988>.

   [RFC6690]  Shelby, Z., "Constrained RESTful Environments (CoRE) Link
              Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
              <https://www.rfc-editor.org/rfc/rfc6690>.

   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252,
              DOI 10.17487/RFC7252, June 2014,
              <https://www.rfc-editor.org/rfc/rfc7252>.

   [RFC7641]  Hartke, K., "Observing Resources in the Constrained
              Application Protocol (CoAP)", RFC 7641,
              DOI 10.17487/RFC7641, September 2015,
              <https://www.rfc-editor.org/rfc/rfc7641>.

   [RFC8075]  Castellani, A., Loreto, S., Rahman, A., Fossati, T., and
              E. Dijk, "Guidelines for Mapping Implementations: HTTP to
              the Constrained Application Protocol (CoAP)", RFC 8075,
              DOI 10.17487/RFC8075, February 2017,
              <https://www.rfc-editor.org/rfc/rfc8075>.

   [RFC8613]  Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
              "Object Security for Constrained RESTful Environments
              (OSCORE)", RFC 8613, DOI 10.17487/RFC8613, July 2019,
              <https://www.rfc-editor.org/rfc/rfc8613>.

   [RFC9176]  Amsüss, C., Ed., Shelby, Z., Koster, M., Bormann, C., and
              P. van der Stok, "Constrained RESTful Environments (CoRE)
              Resource Directory", RFC 9176, DOI 10.17487/RFC9176, April
              2022, <https://www.rfc-editor.org/rfc/rfc9176>.

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Acknowledgements

   The CoRE WG had been discussing setting up a registry for target
   attributes since the final touches were made on [RFC6690].  The
   update of the Web Linking specification to [RFC8288] provided the
   formal setting, but it took until Jaime Jiménez provided the set of
   initial registrations to generate a first version of this
   specification.  The current version addresses additional input and
   working group last call comments by Esko Dijk, Marco Tiloca, and
   Thomas Fossati.

Contributors

   Jaime Jiménez
   Ericsson
   Email: jaime@iki.fi

   Jaime provided the list of initial registrations.

Author's Address

   Carsten Bormann
   Universität Bremen TZI
   Postfach 330440
   D-28359 Bremen
   Germany
   Phone: +49-421-218-63921
   Email: cabo@tzi.org

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