rfc9100.original.xml   rfc9100.xml 
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<front> <front>
<title abbrev="SenML Features and Versions ">SenML Features and Versions</ti <title abbrev="SenML Features and Versions ">Sensor Measurement Lists
tle> (SenML) Features and Versions</title>
<seriesInfo name="Internet-Draft" value="draft-ietf-core-senml-versions-05"/ <seriesInfo name="RFC" value="9100"/>
>
<author initials="C." surname="Bormann" fullname="Carsten Bormann"> <author initials="C." surname="Bormann" fullname="Carsten Bormann">
<organization>Universitaet Bremen TZI</organization> <organization>Universität Bremen TZI</organization>
<address> <address>
<postal> <postal>
<street>Postfach 330440</street> <street>Postfach 330440</street>
<city>Bremen</city> <city>Bremen</city>
<code>D-28359</code> <code>D-28359</code>
<country>Germany</country> <country>Germany</country>
</postal> </postal>
<phone>+49-421-218-63921</phone> <phone>+49-421-218-63921</phone>
<email>cabo@tzi.org</email> <email>cabo@tzi.org</email>
</address> </address>
</author> </author>
<date year="2021" month="June" day="04"/> <date year="2021" month="August"/>
<workgroup>CoRE</workgroup> <workgroup>CoRE</workgroup>
<keyword>Internet-Draft</keyword>
<keyword>Internet of Things (IoT)</keyword>
<keyword>Internet of Things</keyword>
<keyword>IOT</keyword>
<keyword>data model</keyword>
<abstract> <abstract>
<t>This short document updates RFC 8428, Sensor Measurement Lists <t>This short document updates RFC 8428, "Sensor Measurement Lists
(SenML), by specifying the use of independently selectable "SenML (SenML)", by specifying the use of independently selectable "SenML
Features" and mapping them to SenML version numbers.</t> Features" and mapping them to SenML version numbers.</t>
</abstract> </abstract>
<note removeInRFC="true">
<name>Discussion Venues</name>
<t>Discussion of this document takes place on the
CORE Working Group mailing list (core@ietf.org),
which is archived at
<eref target="https://mailarchive.ietf.org/arch/browse/core/">https://mailarchiv
e.ietf.org/arch/browse/core/</eref>.</t>
<t>Source for this draft and an issue tracker can be found at
<eref target="https://github.com/core-wg/senml-versions">https://github.com/core
-wg/senml-versions</eref>.</t>
</note>
</front> </front>
<middle> <middle>
<section anchor="intro" numbered="true" toc="default"> <section anchor="intro" numbered="true" toc="default">
<name>Introduction</name> <name>Introduction</name>
<t>The Sensor Measurement Lists (SenML) specification <xref target="RFC842 <t>The Sensor Measurement Lists (SenML) specification <xref
8" format="default"/> provides a version target="RFC8428" format="default"/> provides a version number that is
number that is initially set to 10, without further initially set to 10, without further specification on the way to make
specification on the way to make use of different version numbers.</t> use of different version numbers.</t>
<t>The traditional idea of using a version number to indicate the <t>The common idea of using a version number to indicate the
evolution of an interchange format generally assumes an incremental evolution of an interchange format generally assumes an incremental
progression of the version number as the format accretes additional progression of the version number as the format accretes additional
features over time. features over time. However, in the case of SenML, it is expected that
However, in the case of SenML, it is expected that the likely evolution the likely evolution will be for independently selectable capability
will be for independently selectable capability <em>features</em> to be added <em>features</em> to be added to the basic specification that is
to the basic specification that is indicated by version number 10. indicated by version number 10. To support this model, this document
To support this model, this document repurposes the single version repurposes the single version number accompanying a pack of SenML
number accompanying a pack of SenML records so that it is interpreted records so that it is interpreted as a bitmap that indicates the set of
as a bitmap that indicates the set of features a recipient would need features a recipient would need to have implemented to be able to
to have implemented to be able to process the pack.</t> process the pack.</t>
<t>This short document specifies the use of SenML Features and maps <t>This short document specifies the use of SenML Features and maps them
them to SenML version number space, updating <xref target="RFC8428" format="defa to SenML version number space, updating <xref target="RFC8428"
ult"/>.</t> format="default"/>.</t>
<section anchor="terminology" numbered="true" toc="default"> <section anchor="terminology" numbered="true" toc="default">
<name>Terminology</name> <name>Terminology</name>
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", <t>The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
"MAY", and "OPTIONAL" in this document are to be interpreted as "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL
described in BCP 14 <xref target="RFC2119" format="default"/> <xref target="RFC8 NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>",
174" format="default"/> when, and only when, they "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
appear in all capitals, as shown here.</t> "<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document
<t>Where bit arithmetic is explained, this document uses the notation are to be interpreted as described in BCP&nbsp;14 <xref target="RFC2119"
familiar from the programming language C <xref target="C" format="default"/>, in format="default"/> <xref target="RFC8174" format="default"/> when, and
cluding the <tt>0b</tt> only when, they appear in all capitals, as shown here.</t>
prefix for binary numbers defined in Section 5.13.2 of the C++
language standard <xref target="Cplusplus" format="default"/>, except that super <t>Where bit arithmetic is explained, this document uses the notation
script notation familiar from the programming language C <xref target="C"
(example for two to the power of 64: 2<sup>64</sup>) denotes format="default"/>, including the <tt>0b</tt> prefix for binary
exponentiation; in the plain text version of this draft, superscript numbers defined in Section 5.13.2 of the C++ language standard <xref
notation is rendered in paragraph text by C-incompatible surrogate target="CPLUSPLUS" format="default"/>, except that superscript
notation as seen in this example, and in display math by a crude notation (example for two to the power of 64: 2<sup>64</sup>) denotes
plaintext representation, as is the sum (Sigma) sign.</t> exponentiation; in the plain text version of this document, superscript
notation is rendered in paragraph text by C-incompatible surrogate
notation as seen in this example, and in display math by a crude
plain text representation, as is the sum (Sigma) sign.</t>
</section> </section>
</section> </section>
<section anchor="codes" numbered="true" toc="default"> <section anchor="codes" numbered="true" toc="default">
<name>Feature Codes and the Version number</name> <name>Feature Codes and the Version Number</name>
<t>The present specification defines "SenML Features", each identified by <t>The present specification defines "SenML Features", each identified
a "feature by a "feature name" (a text string) and a "feature code" (an unsigned
name" (a text string) and a "feature code" (an unsigned integer less integer less than 53).</t>
than 53).</t>
<t>The specific version of a SenML pack is composed of a set of <t>The specific version of a SenML pack is composed of a set of
features. features. The SenML version number (<tt>bver</tt> field) is then a
The SenML version number (<tt>bver</tt> field) is then a bitmap of these bitmap of these features represented as an unsigned integer,
features represented as an unsigned integer, specifically the sum of, specifically the sum of, for each feature present, two taken to the
for each feature present, two taken power of the feature code of that feature (<xref target="bitmap-as-sum"
to the power of the feature code of that feature (<xref target="bitmap-as-sum" f format="default"/>).</t>
ormat="default"/>).</t>
<figure anchor="bitmap-as-sum"> <figure anchor="bitmap-as-sum">
<name>Feature bitmap as a sum of feature bits</name> <name>Feature Bitmap as a Sum (Sigma Symbol) of Feature Bits</name>
<artset> <artset>
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skipping to change at line 169 skipping to change at line 166
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<artwork type="ascii-art" name="" align="left" alt=""><![CDATA[ <artwork type="ascii-art" name="" align="left" alt=""><![CDATA[
__ 52 fc __ 52 fc
version = \ present(fc) ⋅ 2 version = \ present(fc) ⋅ 2
/__ fc = 0 /__ fc = 0
]]></artwork> ]]></artwork>
</artset> </artset>
</figure> </figure>
<t>where present(fc) is 1 if the feature with the feature code <tt>fc</tt> is <t>where present(fc) is 1 if the feature with the feature code <tt>fc</tt> is
present, 0 otherwise. present, 0 otherwise.
(The expression 2<sup>fc</sup> can be implemented as <tt>1 &lt;&lt; fc</tt> in C (The expression 2<sup>fc</sup> can be implemented as <tt>1 &lt;&lt; fc</tt> in C
and related languages.)</t> and related languages.)</t>
<t>RFC editor: Please check that, in the TXT version, no <tt>&amp;nbsp;</t
t> crept
into the above due to xml2rfc bug 641, and remove this paragraph. If
possible with today's RFCXML, add the Sigma character as a parenthesis
after "sum" in the caption.</t>
<section anchor="discussion" numbered="true" toc="default"> <section anchor="discussion" numbered="true" toc="default">
<name>Discussion</name> <name>Discussion</name>
<t>Representing features as a bitmap within a number is quite efficient <t>Representing features as a bitmap within a number is quite
as long as efficient as long as feature codes are sparingly allocated (see also
feature codes are sparingly allocated (see also <xref target="iana" format="defa <xref target="iana" format="default"/>).</t>
ult"/>).</t>
<t>Compatibility with the existing SenML version number, 10 decimal <t>Compatibility with the existing SenML version number, 10 decimal
(0b1010), requires reserving four of the least significant bit (0b1010), requires reserving four of the least significant bit
positions for the base version as described in <xref target="resv" format="defau positions for the base version as described in <xref target="resv"
lt"/>. format="default"/>. There is an upper limit to the range of the
There is an upper limit to the range of the integer numbers that can integer numbers that can be represented in all SenML representations:
be represented in all SenML representations: practical JSON limits practical JSON limits this to 2<sup>53</sup>-1 <xref target="RFC7493"
this to 2<sup>53</sup>-1 <xref target="RFC7493" format="default"/>. format="default"/>. This means the feature codes 4 to 52 are
This means the feature codes 4 to 52 are available, one of which is available, one of which is taken by the feature defined in <xref
taken by the feature defined in <xref target="secondary-units" format="default"/ target="secondary-units" format="default"/>, leaving 48 for
>, leaving 48 for allocation. allocation. (The current version 10 (with all other feature codes
(The current version 10 (with all other feature codes unset) can be unset) can be visualized as
visualized as <tt>0b00000000000000000000000000000000000000000000000001010</tt>.) <tt>0b00000000000000000000000000000000000000000000000001010</tt>.)
For a lifetime of this scheme of several decades, approximately two feature code For a lifetime of this scheme of several decades, approximately two
s feature codes per year or fewer should be allocated. Note that less
per year or fewer should be allocated. generally applicable features can always be communicated via fields
Note that less generally applicable features can always be labeled with names that end with the "_" character ("must-understand
communicated via fields labeled with names that end with the "_" fields"). See <xref section="4.4" sectionFormat="of" target="RFC8428"
character ("must-understand fields"), see <xref section="4.4" sectionFormat="of" format="default"/> for details.</t>
target="RFC8428" format="default"/>.)</t> <t>Most representations visible to engineers working with SenML will
<t>Most representations visible to engineers working with SenML will use use decimal numbers. For instance, 26 (0b11010, 0x1a) denotes a version
decimal numbers, e.g., 26 (0b11010, 0x1a) for a version that adds the that adds
"Secondary Units" feature (<xref target="secondary-units" format="default"/>). the "Secondary Units" feature (<xref target="secondary-units"
This is slightly unwieldy, but format="default"/>). This is slightly unwieldy but will be quickly
will be quickly memorized in practice.</t> memorized in practice.</t>
<t>As a general observation, ending up over time with dozens of <t>As a general observation, ending up over time with dozens of
individually selectable optional extensions may lead to too many individually selectable optional extensions may lead to too many
variants of what is supported by different implementations, reducing variants of what is supported by different implementations, reducing
interoperability. So, in practice, it is still desirable to batch up interoperability. So, in practice, it is still desirable to batch up
extensions that are expected to be supported together into a single extensions that are expected to be supported together into a single
feature bit, leading to a sort of hybrid between completely feature bit, leading to a sort of hybrid between completely
independent extensions and a linear version scheme. This is also independent extensions and a linear version scheme. This is also
another reason why a space of 48 remaining feature codes should another reason why a space of 48 remaining feature codes should
suffice for a while.</t> suffice for a while.</t>
</section> </section>
<section anchor="updating-section-44-of-rfc8428" numbered="true" toc="defa ult"> <section anchor="updating-section-44-of-rfc8428" numbered="true" toc="defa ult">
<name>Updating <xref section="4.4" sectionFormat="of" target="RFC8428" f <name>Updating Section 4.4 of RFC 8428</name>
ormat="default"/></name>
<t>The last paragraph of <xref section="4.4" sectionFormat="of" target=" <t>The last paragraph of <xref section="4.4" sectionFormat="of"
RFC8428" format="default"/> may be read to give target="RFC8428" format="default"/> may be read to give the impression
the impression that SenML version numbers are totally ordered, i.e., that SenML version numbers are totally ordered, i.e., that an
that an implementation that understands version n also always implementation that understands version n also always understands all
understands all versions k &lt; n. versions k &lt; n. If this ever was true for SenML versions before
If this ever was true for SenML versions before 10, it certainly is no 10, it certainly is no longer true with this specification.</t>
longer true with this specification.</t>
<t>Any SenML pack that sets feature bits beyond the first four will <t>Any SenML pack that sets feature bits beyond the first four will
lead to a version number that actually is greater than 10, so the lead to a version number that actually is greater than 10, so the
requirement in <xref section="4.4" sectionFormat="of" target="RFC8428" format="d efault"/> will prevent false requirement in <xref section="4.4" sectionFormat="of" target="RFC8428" format="d efault"/> will prevent false
interoperability with version 10 implementations.</t> interoperability with version 10 implementations.</t>
<t>Implementations that do implement feature bits beyond the first four, <t>Implementations that do implement feature bits beyond the first four,
i.e., versions greater than 10, will instead need to perform a bitwise i.e., versions greater than 10, will instead need to perform a bitwise
comparison of the feature bitmap as described in this specification comparison of the feature bitmap as described in this specification
and ensure that all features indicated are understood before using the and ensure that all features indicated are understood before using the
pack. pack.
E.g., an implementation that implements basic SenML (version number For example, an implementation that implements basic SenML (version number
10) plus only a future feature code 5, will accept version number 42, 10) plus only a future feature code 5 will accept version number 42,
but would not be able to work with a pack indicating version number but it would not be able to work with a pack indicating version number
26 (base specification plus feature code 4). 26 (base specification plus feature code 4).
(If the implementation <em>requires</em> feature code 5 without being (If the implementation <em>requires</em> feature code 5 without being
backwards compatible, it will accept 42, but not 10.)</t> backwards compatible, it will accept 42, but not 10.)</t>
</section> </section>
</section> </section>
<section anchor="resv" numbered="true" toc="default"> <section anchor="resv" numbered="true" toc="default">
<name>Features: Reserved0, Reserved1, Reserved2, Reserved3</name> <name>Features: Reserved0, Reserved1, Reserved2, Reserved3</name>
<t>For SenML Version 10 as described in <xref target="RFC8428" format="def <t>For SenML version 10 as described in <xref target="RFC8428"
ault"/>, the feature codes 0 to 3 are already in use. format="default"/>, the feature codes 0 to 3 are already in use.
Reserved1 (1) and Reserved3 (3) are always present Reserved1 (1) and Reserved3 (3) are always present, and the features
and the features Reserved0 (0) and Reserved2 (2) are always absent, Reserved0 (0) and Reserved2 (2) are always absent, i.e., the four
i.e., the four least significant bits set to 0b1010 indicate a version least significant bits set to 0b1010 indicate a version number of 10 if
number of 10 if no other feature is in use. no other feature is in use. These four reserved feature codes are not
These four reserved feature codes are not to be used with any more specific to be used with any more specific semantics except in a specification
semantics except in a specification that updates the present specification. that updates the present specification. (Note that Reserved0 and
(Note that Reserved0 and Reserved2 could be used in such a Reserved2 could be used in such a specification in a way similar to that
specification in a similar way to the way the feature codes 4 to 52 of feature codes 4 to 52 in the present specification.)</t>
are in the present specification.)</t>
</section> </section>
<section anchor="secondary-units" numbered="true" toc="default"> <section anchor="secondary-units" numbered="true" toc="default">
<name>Feature: Secondary Units</name> <name>Feature: Secondary Units</name>
<t>The feature "Secondary Units" (code number 4) indicates that secondary <t>The feature "Secondary Units" (code number 4) indicates that
unit names <xref target="RFC8798" format="default"/> MAY be used in the "u" fiel secondary unit names <xref target="RFC8798" format="default"/>
d of SenML Records, in addition to the <bcp14>MAY</bcp14> be used in the "u" field of SenML records in addition
primary unit names already allowed by <xref target="RFC8428" format="default"/>. to the primary unit names already allowed by <xref target="RFC8428"
</t> format="default"/>.</t>
<t>Note that the most basic use of this feature simply sets the SenML <t>Note that the most basic use of this feature simply sets the SenML
version number to 26 (10 + 2<sup>4</sup>).</t> version number to 26 (10 + 2<sup>4</sup>).</t>
</section> </section>
<section anchor="seccons" numbered="true" toc="default"> <section anchor="seccons" numbered="true" toc="default">
<name>Security Considerations</name> <name>Security Considerations</name>
<t>The security considerations of <xref target="RFC8428" format="default"/ > apply. <t>The security considerations of <xref target="RFC8428" format="default"/ > apply.
This specification provides structure to the interpretation of the This specification provides structure to the interpretation of the
SenML version number, which poses no additional security SenML version number, which poses no additional security
considerations except for some potential for surprise that version considerations except for some potential for surprise that version
numbers do not simply increase linearly.</t> numbers do not simply increase linearly.</t>
</section> </section>
<section anchor="iana" numbered="true" toc="default"> <section anchor="iana" numbered="true" toc="default">
<name>IANA Considerations</name> <name>IANA Considerations</name>
<t>IANA is requested to create a new subregistry "SenML features" within t <t>IANA has created a new "<xref section="SenML Features"
he SenML sectionFormat="bare" target="IANA.SENML" relative="#senml-features"/>"
registry <xref target="IANA.senml" format="default"/>, with the registration pol subregistry within the "Sensor Measurement Lists (SenML)" registry <xref
icy "specification required" <xref target="RFC8126" format="default"/> target="IANA.SENML" format="default"/> with the registration policy
and the columns:</t> "Specification Required" <xref target="RFC8126" format="default"/> and
the columns:</t>
<ul spacing="normal"> <ul spacing="normal">
<li>Feature code (an unsigned integer less than 53)</li> <li>Feature Code (an unsigned integer less than 53)</li>
<li>Feature name (text)</li> <li>Feature Name (text)</li>
<li>Specification</li> <li>Reference</li>
</ul> </ul>
<t>To facilitate the use of feature names in programs, the designated <t>To facilitate the use of feature names in programs, the designated
expert is requested to ensure that feature names are usable as expert is requested to ensure that feature names are usable as
identifiers in most programming languages, after lower-casing the identifiers in most programming languages, after lowercasing the feature
feature name in the registry entry and replacing whitespace with name in the registry entry and replacing blank space with underscores or
underscores or hyphens, and that they also are distinct in this form.</t> hyphens, and that they also are distinct in this form.</t>
<t>The initial content of this registry is as follows:</t> <t>The initial content of this registry is as follows:</t>
<table anchor="feat" align="center"> <table anchor="feat" align="center">
<name>Features defined for SenML at the time of writing</name> <name>Features Defined for SenML at the Time of Writing</name>
<thead> <thead>
<tr> <tr>
<th align="left">Feature code</th> <th align="left">Feature Code</th>
<th align="left">Feature name</th> <th align="left">Feature Name</th>
<th align="left">Specification</th> <th align="left">Reference</th>
</tr> </tr>
</thead> </thead>
<tbody> <tbody>
<tr> <tr>
<td align="left">0</td> <td align="left">0</td>
<td align="left">Reserved0</td> <td align="left">Reserved0</td>
<td align="left">RFCthis</td> <td align="left">[RFC9100]</td>
</tr> </tr>
<tr> <tr>
<td align="left">1</td> <td align="left">1</td>
<td align="left">Reserved1</td> <td align="left">Reserved1</td>
<td align="left">RFCthis</td> <td align="left">[RFC9100]</td>
</tr> </tr>
<tr> <tr>
<td align="left">2</td> <td align="left">2</td>
<td align="left">Reserved2</td> <td align="left">Reserved2</td>
<td align="left">RFCthis</td> <td align="left">[RFC9100]</td>
</tr> </tr>
<tr> <tr>
<td align="left">3</td> <td align="left">3</td>
<td align="left">Reserved3</td> <td align="left">Reserved3</td>
<td align="left">RFCthis</td> <td align="left">[RFC9100]</td>
</tr> </tr>
<tr> <tr>
<td align="left">4</td> <td align="left">4</td>
<td align="left">Secondary Units</td> <td align="left">Secondary Units</td>
<td align="left">RFCthis, <xref target="RFC8798" format="default"/>< /td> <td align="left">[RFC9100] <xref target="RFC8798" format="default"/> </td>
</tr> </tr>
</tbody> </tbody>
</table> </table>
<t>As the number of features that can be registered has a hard limit (48 <t>As the number of features that can be registered has a hard limit (48
codes left at the time of writing), the designated expert is codes left at the time of writing), the designated expert is
specifically instructed to maintain a frugal regime of code point specifically instructed to maintain a frugal regime of code point
allocation, keeping code points available for SenML Features that are allocation, keeping code points available for SenML Features that are
likely to be useful for non-trivial subsets of the SenML ecosystem. likely to be useful for non-trivial subsets of the SenML ecosystem.
Quantitatively, the expert could for instance steer the allocation to Quantitatively, the expert could, for instance, steer the allocation to
a target of not allocating more than 10 % of the remaining set per year.</t> a target of not allocating more than 10% of the remaining set per year.</t>
<t>Where the specification of the feature code is provided in a document <t>Where the specification of the feature code is provided in a document
that is separate from the specification of the feature itself (as with that is separate from the specification of the feature itself (as with
feature code 4 above), both specifications should be listed.</t> feature code 4 above), both specifications should be listed.</t>
</section> </section>
</middle> </middle>
<back> <back>
<references> <references>
<name>References</name> <name>References</name>
<references> <references>
<name>Normative References</name> <name>Normative References</name>
<reference anchor="RFC8428" target="https://www.rfc-editor.org/info/rfc8
428"> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8428.
<front> xml"/>
<title>Sensor Measurement Lists (SenML)</title> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8126.
<author fullname="C. Jennings" initials="C." surname="Jennings"> xml"/>
<organization/>
</author> <reference anchor="IANA.SENML" target="https://www.iana.org/assignments/
<author fullname="Z. Shelby" initials="Z." surname="Shelby"> senml">
<organization/>
</author>
<author fullname="J. Arkko" initials="J." surname="Arkko">
<organization/>
</author>
<author fullname="A. Keranen" initials="A." surname="Keranen">
<organization/>
</author>
<author fullname="C. Bormann" initials="C." surname="Bormann">
<organization/>
</author>
<date month="August" year="2018"/>
<abstract>
<t>This specification defines a format for representing simple sen
sor measurements and device parameters in Sensor Measurement Lists (SenML). Rep
resentations are defined in JavaScript Object Notation (JSON), Concise Binary Ob
ject Representation (CBOR), Extensible Markup Language (XML), and Efficient XML
Interchange (EXI), which share the common SenML data model. A simple sensor, su
ch as a temperature sensor, could use one of these media types in protocols such
as HTTP or the Constrained Application Protocol (CoAP) to transport the measure
ments of the sensor or to be configured.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="8428"/>
<seriesInfo name="DOI" value="10.17487/RFC8428"/>
</reference>
<reference anchor="RFC8126" target="https://www.rfc-editor.org/info/rfc8
126">
<front>
<title>Guidelines for Writing an IANA Considerations Section in RFCs
</title>
<author fullname="M. Cotton" initials="M." surname="Cotton">
<organization/>
</author>
<author fullname="B. Leiba" initials="B." surname="Leiba">
<organization/>
</author>
<author fullname="T. Narten" initials="T." surname="Narten">
<organization/>
</author>
<date month="June" year="2017"/>
<abstract>
<t>Many protocols make use of points of extensibility that use con
stants to identify various protocol parameters. To ensure that the values in th
ese fields do not have conflicting uses and to promote interoperability, their a
llocations are often coordinated by a central record keeper. For IETF protocols
, that role is filled by the Internet Assigned Numbers Authority (IANA).</t>
<t>To make assignments in a given registry prudently, guidance des
cribing the conditions under which new values should be assigned, as well as whe
n and how modifications to existing values can be made, is needed. This documen
t defines a framework for the documentation of these guidelines by specification
authors, in order to assure that the provided guidance for the IANA Considerati
ons is clear and addresses the various issues that are likely in the operation o
f a registry.</t>
<t>This is the third edition of this document; it obsoletes RFC 52
26.</t>
</abstract>
</front>
<seriesInfo name="BCP" value="26"/>
<seriesInfo name="RFC" value="8126"/>
<seriesInfo name="DOI" value="10.17487/RFC8126"/>
</reference>
<reference anchor="IANA.senml" target="http://www.iana.org/assignments/s
enml">
<front> <front>
<title>Sensor Measurement Lists (SenML)</title> <title>Sensor Measurement Lists (SenML)</title>
<author> <author>
<organization>IANA</organization> <organization>IANA</organization>
</author> </author>
<date/> <date/>
</front> </front>
</reference> </reference>
<reference anchor="RFC8798" target="https://www.rfc-editor.org/info/rfc8
798"> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8798.
<front> xml"/>
<title>Additional Units for Sensor Measurement Lists (SenML)</title>
<author fullname="C. Bormann" initials="C." surname="Bormann">
<organization/>
</author>
<date month="June" year="2020"/>
<abstract>
<t>The Sensor Measurement Lists (SenML) media type supports the in
dication of units for a quantity represented. This short document registers a n
umber of additional unit names in the IANA registry for units in SenML. It also
defines a registry for secondary units that cannot be in SenML's main registry,
as they are derived by linear transformation from units already in that registr
y.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="8798"/>
<seriesInfo name="DOI" value="10.17487/RFC8798"/>
</reference>
<reference anchor="C" target="https://www.iso.org/standard/74528.html"> <reference anchor="C" target="https://www.iso.org/standard/74528.html">
<front> <front>
<title>Information technology — Programming languages — C</title> <title>Information technology - Programming languages - C</title>
<author> <author>
<organization>International Organization for Standardization</orga nization> <organization>International Organization for Standardization</orga nization>
</author> </author>
<date year="2018" month="June"/> <date year="2018" month="June"/>
</front> </front>
<seriesInfo name="ISO/IEC" value="9899:2018, Fourth Edition"/> <seriesInfo name="ISO/IEC" value="9899:2018, Fourth Edition"/>
</reference> </reference>
<reference anchor="Cplusplus" target="https://www.iso.org/standard/79358
.html"> <reference anchor="CPLUSPLUS" target="https://www.iso.org/standard/79358
.html">
<front> <front>
<title>Programming languages — C++</title> <title>Programming languages - C++</title>
<author> <author>
<organization>International Organization for Standardization</orga nization> <organization>International Organization for Standardization</orga nization>
</author> </author>
<date year="2020" month="December"/> <date year="2020" month="December"/>
</front> </front>
<seriesInfo name="ISO/IEC" value="14882:2020, Sixth Edition"/> <seriesInfo name="ISO/IEC" value="14882:2020, Sixth Edition"/>
</reference> </reference>
<reference anchor="RFC2119" target="https://www.rfc-editor.org/info/rfc2
119"> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.
<front> xml"/>
<title>Key words for use in RFCs to Indicate Requirement Levels</tit <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8174.
le> xml"/>
<author fullname="S. Bradner" initials="S." surname="Bradner">
<organization/>
</author>
<date month="March" year="1997"/>
<abstract>
<t>In many standards track documents several words are used to sig
nify the requirements in the specification. These words are often capitalized.
This document defines these words as they should be interpreted in IETF document
s. This document specifies an Internet Best Current Practices for the Internet
Community, and requests discussion and suggestions for improvements.</t>
</abstract>
</front>
<seriesInfo name="BCP" value="14"/>
<seriesInfo name="RFC" value="2119"/>
<seriesInfo name="DOI" value="10.17487/RFC2119"/>
</reference>
<reference anchor="RFC8174" target="https://www.rfc-editor.org/info/rfc8
174">
<front>
<title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</ti
tle>
<author fullname="B. Leiba" initials="B." surname="Leiba">
<organization/>
</author>
<date month="May" year="2017"/>
<abstract>
<t>RFC 2119 specifies common key words that may be used in protoco
l specifications. This document aims to reduce the ambiguity by clarifying tha
t only UPPERCASE usage of the key words have the defined special meanings.</t>
</abstract>
</front>
<seriesInfo name="BCP" value="14"/>
<seriesInfo name="RFC" value="8174"/>
<seriesInfo name="DOI" value="10.17487/RFC8174"/>
</reference>
</references> </references>
<references> <references>
<name>Informative References</name> <name>Informative References</name>
<reference anchor="RFC7493" target="https://www.rfc-editor.org/info/rfc7
493"> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7493.
<front> xml"/>
<title>The I-JSON Message Format</title>
<author fullname="T. Bray" initials="T." role="editor" surname="Bray
">
<organization/>
</author>
<date month="March" year="2015"/>
<abstract>
<t>I-JSON (short for "Internet JSON") is a restricted profile of J
SON designed to maximize interoperability and increase confidence that software
can process it successfully with predictable results.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="7493"/>
<seriesInfo name="DOI" value="10.17487/RFC7493"/>
</reference>
</references> </references>
</references> </references>
<section numbered="false" anchor="acks" toc="default"> <section numbered="false" anchor="acks" toc="default">
<name>Acknowledgements</name> <name>Acknowledgements</name>
<t><contact fullname="Ari Keränen"/> proposed to use the version number as <t><contact fullname="Ari Keränen"/> proposed to use the version number
a bitmap and as a bitmap and provided further input on this specification. <contact
provided further input on this specification. fullname="Jaime Jiménez"/> helped clarify the document by providing a
<contact fullname="Jaime Jiménez"/> helped clarify the document by providing a r review and acted as Document Shepherd. <contact fullname="Elwyn Davies"/>
eview. provided a detailed GENART
<contact fullname="Elwyn Davies"/> provided a detailed GENART review, with direc review with directly implementable text suggestions that now form part
tly of this specification. <contact fullname="Rob Wilton"/> supplied
implementable text suggestions that now form part of this specification. comments, one of which became the last paragraph of <xref
<contact fullname="Rob Wilton"/> supplied comments one of which became the last target="discussion" format="default"/>; <contact fullname="Éric
paragraph of <xref target="discussion" format="default"/>; <contact fullname="Ér Vyncke"/> helped with <xref target="codes" format="default"/>.
ic Vyncke"/> helped with <xref target="codes" format="default"/>. Additional thanks go to the other IESG reviewers.</t>
Additional thanks go to the other IESG reviewers.</t>
<!-- LocalWords: selectable subregistry whitespace
-->
</section> </section>
</back> </back>
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