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CoRE Target Attributes Registry
draft-ietf-core-target-attr-06

Document Type Active Internet-Draft (core WG)
Author Carsten Bormann
Last updated 2024-02-01 (Latest revision 2023-10-11)
Replaces draft-bormann-core-target-attr
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Informational
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Stream WG state Submitted to IESG for Publication
Associated WG milestone
May 2023
Creation of IANA registry for CoRE target attributes submitted to IESG as Informational RFC
Document shepherd Marco Tiloca
Shepherd write-up Show Last changed 2023-07-23
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Responsible AD Robert Wilton
Send notices to marco.tiloca@ri.se
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Details
draft-ietf-core-target-attr-06
CoRE Working group                                            C. Bormann
Internet-Draft                                    Universität Bremen TZI
Intended status: Informational                           11 October 2023
Expires: 13 April 2024

                    CoRE Target Attributes Registry
                     draft-ietf-core-target-attr-06

Abstract

   The Constrained RESTful Environments (CoRE) specifications apply Web
   technologies to constrained environments.  One important such
   technology is Web Linking (RFC 8288), which CoRE specifications use
   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 (RD, 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 document introduces an IANA registry for
   coordinating names of target attributes when used in CoRE.  It
   updates the RD Parameters IANA Registry created by 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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   Drafts is at https://datatracker.ietf.org/drafts/current/.

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   time.  It is inappropriate to use Internet-Drafts as reference
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   This Internet-Draft will expire on 13 April 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
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   provided without warranty as described in the Revised BSD License.

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 specifications use 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 document introduces an IANA registry for coordinating names of
   target attributes when used in CoRE, with specific instructions for
   the Designated Expert for this registry (Section 2.1).  It updates
   the RD Parameters IANA Registry created by [RFC9176] to coordinate
   with this registry.

   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 creates a new Target Attributes registry in the
   "Constrained RESTful Environments (CoRE) Parameters" registry group
   [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 requested to guide the registrant towards reasonably
   short target attribute names where the shortness will help conserve
   resources in constrained systems, but also to be frugal in the
   allocation of very short 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 registry are listed in Table 1.

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

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   +-----------+-------------------------+------------+---------------+
   | ep        | Endpoint Name (with     | IETF       | Section 9.3   |
   |           | rt="core.rd-ep")        |            | of [RFC9176]  |
   +-----------+-------------------------+------------+---------------+
   | d         | Sector (with            | IETF       | Section 9.3   |
   |           | rt="core.rd-ep")        |            | of [RFC9176]  |
   +-----------+-------------------------+------------+---------------+
   | base      | Registration Base URI   | IETF       | Section 9.3   |
   |           | (with rt="core.rd-ep")  |            | of [RFC9176]  |
   +-----------+-------------------------+------------+---------------+
   | et        | Endpoint Type (with     | IETF       | 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.  A further set of target
   attributes is predefined in [RFC8288] and is imported into this
   registry.

   Section 9.3 of [RFC9176] created the "RD Parameters" IANA registry.
   This document requests IANA to add the following note to that
   registry:

      Note: In accordance with [this document], all entries with the "A"
      flag set, including new ones, MUST also be registered in the
      "Target Attributes" registry [IANA.core-parameters].

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>.

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   [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>.

   [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>.

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   [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>.

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, Thomas
   Fossati, and Mohamed Boucadair, as well as area director review
   comments from Rob Wilton.

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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