Internet DRAFT - draft-ietf-core-target-attr
draft-ietf-core-target-attr
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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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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