Constrained RESTful Environments T. Fossati
Internet-Draft Linaro
Updates: 7252 (if approved) E. Dijk
Intended status: Standards Track IoTconsultancy.nl
Expires: 13 September 2025 12 March 2025
Update to the IANA CoAP Content-Formats Registration Procedures
draft-ietf-core-cf-reg-update-06
Abstract
This document updates RFC7252 regarding the registration procedures
for the "CoAP Content-Formats" IANA registry, within the "Constrained
RESTful Environments (CoRE) Parameters" registry group. This
document also introduces a new column, "Media Type", to the registry.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at https://core-
wg.github.io/cf-reg-update/draft-ietf-core-cf-reg-update.html.
Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-ietf-core-cf-reg-update/.
Discussion of this document takes place on the Constrained RESTful
Environments 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/cf-reg-update.
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."
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This Internet-Draft will expire on 13 September 2025.
Copyright Notice
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document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3
3. Examples for Erroneous Registrations . . . . . . . . . . . . 3
3.1. The Media Type is Unknown . . . . . . . . . . . . . . . . 4
3.2. The Media Type Parameter is Unknown . . . . . . . . . . . 4
3.3. The Media Type Parameter Value is Invalid . . . . . . . . 4
3.4. The Content Coding is Unknown . . . . . . . . . . . . . . 5
3.5. Duplicate Entry with Default Media Type Parameters . . . 5
3.6. Duplicate Entry with Default Content Coding . . . . . . . 6
3.7. Duplicate Entry with Equivalent Parameter . . . . . . . . 6
4. Updates to RFC 7252 . . . . . . . . . . . . . . . . . . . . . 7
4.1. Updates to Section 12.3 "CoAP Content-Formats
Registry" . . . . . . . . . . . . . . . . . . . . . . . . 7
4.2. New Section 12.3.1 "Temporary Content-Format
Registrations" . . . . . . . . . . . . . . . . . . . . . 9
4.3. New Section 12.3.2 "Adding the Media Type Column to the
Registry" . . . . . . . . . . . . . . . . . . . . . . . . 10
4.4. New Section 12.3.3 "Expert Review Procedure" . . . . . . 10
4.5. New Section 12.3.4 "Preferred Format for the Content Type
Field" . . . . . . . . . . . . . . . . . . . . . . . . . 11
5. Security Considerations . . . . . . . . . . . . . . . . . . . 12
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
6.1. Temporary Note Removal . . . . . . . . . . . . . . . . . 12
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.1. Normative References . . . . . . . . . . . . . . . . . . 12
7.2. Informative References . . . . . . . . . . . . . . . . . 13
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
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1. Introduction
Section 12.3 of [RFC7252] describes the registration procedures for
the "CoAP Content-Formats" IANA registry within the "Constrained
RESTful Environments (CoRE) Parameters" registry group
[IANA.core-parameters]. (Note that the columns of this registry have
been revised according to [Err4954].)
In particular, the text defines the rules for obtaining CoAP Content-
Format identifiers from the "IETF Review" or "IESG Approval" range of
the registry (256-9999) as well as from the First Come First Served
(FCFS) range of the registry (10000-64999). For the FCFS range,
these rules do not involve the Designated Expert (DE) and are managed
solely by IANA personnel to finalize the registration.
Unfortunately, the instructions do not explicitly require checking
that the combination of content-type (i.e., media type with optional
parameters) and content coding associated with the requested CoAP
Content-Format is semantically valid. This task is generally non-
trivial, requires knowledge from multiple documents and technologies,
and should not be solely demanded from the registrar. This lack of
guidance may engender confusion in both the registering party and the
registrar, and has already led to erroneous registrations.
In Section 4.1, this document updates [RFC7252] by modifying the
registration procedures for the "CoAP Content-Formats" registry to
mitigate the risk of unintentional or malicious errors. These
updates amend the different ranges of the registry, introduce a
review procedure to be performed for most ranges of the registry, and
allow the registration of temporary Content-Format identifiers. This
document also introduces a new column, "Media Type", to the registry.
2. Conventions and Definitions
This document uses the terms "media type", "content coding",
"content-type", and "content format" as defined in Section 2 of
[RFC9193].
3. Examples for Erroneous Registrations
This section provides examples of registration requests for the "CoAP
Content-Formats" Registry (as defined in Section 12.3 of [RFC7252]
and revised according to [Err4954]) that are invalid but would be
approved under the current procedure. The checklist defined in
Section 4.4 should prevent any of these attempts from succeeding.
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All the example registration requests use a CoAP Content-Format with
identifier 64999 in the FCFS range of the "CoAP Content-Formats"
registry.
For each of the following example registration requests, one can
create a similar instance where the requested registration is for a
CoAP Content-Format identifier within the "IETF Review" or "IESG
Approval" range of the registry. Similarly, such registrations must
not be allowed to succeed.
3.1. The Media Type is Unknown
The registrant requests an FCFS Content-Format ID for an unknown
media type:
+==========================+================+=======+
| Content Type | Content Coding | ID |
+==========================+================+=======+
| application/unknown+cbor | - | 64999 |
+--------------------------+----------------+-------+
Table 1: Attempt at Registering Content-Format
for an Unknown Media Type
3.2. The Media Type Parameter is Unknown
The registrant requests an FCFS Content-Format ID for an existing
media type with an unknown parameter:
+======================================+================+=======+
| Content Type | Content Coding | ID |
+======================================+================+=======+
| application/cose;unknown-parameter=1 | - | 64999 |
+--------------------------------------+----------------+-------+
Table 2: Attempt at Registering Content-Format for Media Type
with Unknown Parameter
3.3. The Media Type Parameter Value is Invalid
The registrant requests an FCFS Content-Format ID for an existing
media type with an invalid parameter value:
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+====================================+================+=======+
| Content Type | Content Coding | ID |
+====================================+================+=======+
| application/cose;cose-type=invalid | - | 64999 |
+------------------------------------+----------------+-------+
Table 3: Attempt at Registering Content-Format for Media
Type with Invalid Parameter Value
3.4. The Content Coding is Unknown
The registrant requests an FCFS Content-Format ID for an existing
media type with an unknown content coding:
+========================+================+=======+
| Content Type | Content Coding | ID |
+========================+================+=======+
| application/senml+cbor | inflate | 64999 |
+------------------------+----------------+-------+
Table 4: Attempt at Registering Content-Format
with Unknown Content Coding
3.5. Duplicate Entry with Default Media Type Parameters
The registrant requests an FCFS Content-Format ID for a media type
that includes a parameter set to its default value, while a
(hypothetical) Content-Format ID 64900 is already registered for this
media type without that parameter. As a result, this could lead to
the creation of two separate Content-Format IDs for the same
"logical" entry.
+==================================+================+=======+
| Content Type | Content Coding | ID |
+==================================+================+=======+
| application/my | - | 64900 |
+----------------------------------+----------------+-------+
| application/my;parameter=default | - | 64999 |
+----------------------------------+----------------+-------+
Table 5: Attempt at Registering an Equivalent Logical
Entry with a Different Content-Format ID (1)
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3.6. Duplicate Entry with Default Content Coding
The registrant requests an FCFS Content-Format ID for the "identity"
Content Coding, which is the default coding. If accepted, this
request would duplicate an entry with (hypothetical) Content-Format
ID 64900 where the "Content Coding" field is left empty.
+================+================+=======+
| Content Type | Content Coding | ID |
+================+================+=======+
| application/my | - | 64900 |
+----------------+----------------+-------+
| application/my | identity | 64999 |
+----------------+----------------+-------+
Table 6: Attempt at Registering an
Equivalent Logical Entry with a
Different Content-Format ID (2)
3.7. Duplicate Entry with Equivalent Parameter
The registrant requests an FCFS Content-Format ID for a media type
that includes a parameter. The value of this parameter appears
distinct from that of a (hypothetical) previously registered Content-
Format ID 64900 that also includes this parameter. However, the
semantics of the parameter value are identical to the existing
registration.
In this example, the eat_profile parameter value (which can be any
URI) is set as a Uniform Resource Name (URN) [RFC8141]. Since for
URNs, the Namespace Identifier (foo in the example) is defined as
case insensitive, the two registrations are semantically identical.
+=================================+================+=======+
| Content Type | Content Coding | ID |
+=================================+================+=======+
| application/ | - | 64900 |
| eat+cwt;eat_profile="urn:foo:1" | | |
+---------------------------------+----------------+-------+
| application/ | - | 64999 |
| eat+cwt;eat_profile="urn:FOO:1" | | |
+---------------------------------+----------------+-------+
Table 7: Attempt at Registering an Equivalent Logical
Entry with a Different Content-Format ID (3)
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4. Updates to RFC 7252
This section updates Section 12.3 of [RFC7252] and introduces four
new “virtual†subsections, 12.3.1 to 12.3.4.
4.1. Updates to Section 12.3 "CoAP Content-Formats Registry"
// RFC Editor: in this section, please replace RFCthis with the RFC
// number assigned to this document and remove this note.
The CoAP Content-Formats registration procedures defined in
Section 12.3 of [RFC7252] are modified as shown in Table 8.
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+=============+==============+======================================+
| Range | Registration | Notes |
| | Procedures | |
+=============+==============+======================================+
| 0-255 | Expert | Review procedure described in |
| | Review | RFCthis, Section 4.4 |
+-------------+--------------+--------------------------------------+
| 256-9999 | IETF Review | Review procedure described in |
| | with Expert | RFCthis, Section 4.4 |
| | Review or | |
| | IESG | |
| | Approval | |
| | with Expert | |
| | Review | |
+-------------+--------------+--------------------------------------+
| 10000-64999 | Expert | Review procedure described in |
| | Review or | RFCthis, Section 4.4. |
| | First Come | |
| | First Served | FCFS is allowed if the |
| | (FCFS) | registration: |
| | | * has no parameters, and |
| | | * has an empty Content Coding, and |
| | | * the media type is not yet used |
| | | in this registry, and |
| | | * the media type is registered (or |
| | | approved for registration) in the |
| | | "Media Types" registry |
| | | [IANA.media-types]. |
| | | |
| | | Expert Review is required in all |
| | | other cases. |
+-------------+--------------+--------------------------------------+
| 65000-65535 | Experimental | No operational use |
| | Use | |
+-------------+--------------+--------------------------------------+
Table 8: Updated CoAP Content-Formats Registration Procedures
The 256-9999 range now has registration procedures requiring "IETF
Review with Expert Review" or "IESG Approval with Expert Review." In
particular:
* All assignments according to "IETF Review with Expert Review" are
made on an "IETF Review" basis per Section 4.8 of [BCP26] with
"Expert Review" additionally required per Section 4.5 of [BCP26].
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The procedure for early IANA allocation of "standards track code
points" defined in [RFC7120] also applies. When such a procedure
is used, IANA will ask the Designated Expert(s) to approve the
early allocation before registration. In addition, working group
chairs are encouraged to consult the Expert(s) early during the
process outlined in Section 3.1 of [RFC7120].
* All assignments according to "IESG Approval with Expert Review"
are made on an "IESG Approval" basis per Section 4.10 of [BCP26]
with "Expert Review" additionally required per Section 4.5 of
[BCP26].
The 10000-64999 range now has two separate registration procedures.
If the registration consists solely of a registered media type name
in the "Content Type" field, without any parameter names or "Content
Coding", and the media type has not yet been used in this registry,
then the policy is FCFS, as before. In all other cases, the policy
is "Expert Review," following the procedure described in Section 4.4.
A new column with the title "Notes" has been added to the CoAP
Content-Formats Registration Procedures shown in Table 8.
4.2. New Section 12.3.1 "Temporary Content-Format Registrations"
This section clarifies that the "CoAP Content-Formats" registry
allows temporary registrations within the 0-255, 256-9999, and
10000-64999 ranges.
A temporary registration may be created for example by an IANA early
allocation action [RFC7120]. If the referenced media type is
provisional (that is, included in the IANA "Provisional Standard
Media Type" registry [IANA.provisional-standard-media-types]) then a
created registration is always temporary.
A temporary registration is marked as such by IANA in the
corresponding registry entry. Once the required registration
procedure (defined in Table 8) for the temporary ID has successfully
completed, and the referenced media type is included in the IANA
Media Types registry [IANA.media-types], IANA must remove any
indication about the temporary nature of the registration so that the
entry becomes permanent.
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If a temporary registration does not successfully complete the
registration procedure, IANA must remove the entry and set the
Content-Format ID value back to "Unassigned". This may happen for
example when an Internet-Draft requesting a Content-Format ID is
abandoned. If a temporary registration (in any range) refers to a
provisional media type that is abandoned, IANA must remove the entry
and set the Content-Format ID value back to "Unassigned".
Note that in the 10000-64999 range the abandonment of a document
requesting a Content-Format ID does not cause an entry to be removed.
That is because the required registration procedure for this range
does not require completion of any standards process, nor does it
require a registering document.
4.3. New Section 12.3.2 "Adding the Media Type Column to the Registry"
To assist users of the "CoAP Content-Formats" registry in finding
detailed information about the media type associated with each CoAP
Content-Format, and to ensure that a media type exists before a new
entry can be registered, IANA is requested to add a new column "Media
Type" to the registry. This new column is placed directly to the
right of the existing "Content Type" column.
The "Media Type" field for each entry lists the (base) media type
name and provides a hyperlink to registration information for that
media type as recorded by IANA. If the media type is provisional,
the hyperlink points to the IANA "Provisional Standard Media Type"
registry [IANA.provisional-standard-media-types]. If a provisional
media type becomes a permanent media type, IANA must update the
"Media Type" field in the associated registry entries to ensure the
hyperlink directs to the registration information for that media
type.
Note that the registration request procedure remains unchanged. A
requester does not need to fill out the "Media Type" field
separately, as the necessary information is already provided in the
"Content Type" field of the request.
4.4. New Section 12.3.3 "Expert Review Procedure"
The Designated Expert (DE) is instructed to perform the Expert
Review, as described by the following checklist:
1. The combination of content-type and content coding for which the
registration is requested must not be already present in the
"CoAP Content-Formats" registry;
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2. The media type associated with the requested Content-Format must
either be registered in the "Media Types" registry
[IANA.media-types] or approved for registration. Alternatively,
it may be listed in the "Provisional Standard Media Type"
registry [IANA.provisional-standard-media-types]. The use of
provisional standard media types is only permitted for Content-
Format identifiers within the ranges of 0-255 and 256-9999;
3. The optional parameter names must have been defined in
association with the media type, and any parameter values
associated with such parameter names must be as permitted;
4. The Content Type must be in the preferred format defined in
Section 4.5;
5. If a Content Coding is specified, it must exist (or must have
been approved for registration) in the "HTTP Content Coding"
registry of the "Hypertext Transfer Protocol (HTTP) Parameters"
[IANA.http-parameters].
For the 0-255 range, in addition to the checks described above, the
DE is instructed to also evaluate the requested codepoint concerning
the limited availability of the 1-byte codepoint space. For the
256-9999 range and the 10000-64999 range, a similar criterion may
also apply where combinations of media type parameters and content
coding choices consume considerable codepoint space.
4.5. New Section 12.3.4 "Preferred Format for the Content Type Field"
This section defines the preferred string format for including a
requested Content Type into the "CoAP Content-Formats" registry.
During the review process, the Designated Expert(s) or IANA may
rewrite a requested Content Type into this preferred string format
before approval.
The preferred string format is as defined in Section 8.3.1 of
[RFC9110] and follows these rules:
1. For any case-insensitive elements, lowercase characters are used.
2. Parameter values are only quoted if the value is such that it
requires use of quoted-string per Section 5.6.6 of [RFC9110].
Otherwise, a parameter value is included unquoted.
3. A single semicolon character without any adjacent whitespace
characters is used as the separator between media type and
parameters.
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5. Security Considerations
This document hardens the registration procedures of CoAP Content-
Formats in ways that reduce the chances of malicious manipulation of
the associated registry.
Other than that, it does not change the Security Considerations of
[RFC7252].
6. IANA Considerations
This document updates the IANA procedures defined in [RFC7252] for
registering CoAP Content-Formats as described in Section 4.
6.1. Temporary Note Removal
This section is to be removed before publishing as an RFC.
The following note has been added to the registry as a temporary fix:
"Note: The validity of the combination of Content Coding, Content
Type and parameters is checked prior to assignment."
IANA is instructed to remove this note from the registry when this
document is approved for publication. RFC-Editor: please remove this
section once the note has been removed.
7. References
7.1. 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>.
[IANA.http-parameters]
IANA, "Hypertext Transfer Protocol (HTTP) Parameters",
<https://www.iana.org/assignments/http-parameters>.
[IANA.media-types]
IANA, "Media Types",
<https://www.iana.org/assignments/media-types>.
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[IANA.provisional-standard-media-types]
IANA, "Provisional Standard Media Type Registry",
<https://www.iana.org/assignments/provisional-standard-
media-types>.
[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/rfc/rfc7120>.
[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>.
[RFC9110] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/rfc/rfc9110>.
[RFC9193] Keränen, A. and C. Bormann, "Sensor Measurement Lists
(SenML) Fields for Indicating Data Value Content-Format",
RFC 9193, DOI 10.17487/RFC9193, June 2022,
<https://www.rfc-editor.org/rfc/rfc9193>.
7.2. Informative References
[Err4954] RFC Errata Report 4954, RFC 7252,
<https://www.rfc-editor.org/errata/eid4954>.
[RFC8141] Saint-Andre, P. and J. Klensin, "Uniform Resource Names
(URNs)", RFC 8141, DOI 10.17487/RFC8141, April 2017,
<https://www.rfc-editor.org/rfc/rfc8141>.
Acknowledgments
Thank you Amanda Baber, Carsten Bormann, Christer Holmberg, Francesca
Palombini, Marco Tiloca, and Rich Salz for your reviews, comments,
suggestions, and fixes.
Authors' Addresses
Thomas Fossati
Linaro
Email: thomas.fossati@linaro.org
Esko Dijk
IoTconsultancy.nl
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Email: esko.dijk@iotconsultancy.nl
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