rfc9581.original   rfc9581.txt 
Network Working Group C. Bormann Internet Engineering Task Force (IETF) C. Bormann
Internet-Draft Universität Bremen TZI Request for Comments: 9581 Universität Bremen TZI
Intended status: Standards Track B. Gamari Category: Standards Track B. Gamari
Expires: 2 May 2024 Well-Typed ISSN: 2070-1721 Well-Typed
H. Birkholz H. Birkholz
Fraunhofer SIT Fraunhofer SIT
30 October 2023 May 2024
Concise Binary Object Representation (CBOR) Tags for Time, Duration, and Concise Binary Object Representation (CBOR) Tags for Time, Duration, and
Period Period
draft-ietf-cbor-time-tag-12
Abstract Abstract
The Concise Binary Object Representation (CBOR, RFC 8949) is a data The Concise Binary Object Representation (CBOR, RFC 8949) is a data
format whose design goals include the possibility of extremely small format whose design goals include the possibility of extremely small
code size, fairly small message size, and extensibility without the code size, fairly small message size, and extensibility without the
need for version negotiation. need for version negotiation.
In CBOR, one point of extensibility is the definition of CBOR tags. In CBOR, one point of extensibility is the definition of CBOR tags.
RFC 8949 defines two tags for time: CBOR tag 0 (RFC3339 time as a RFC 8949 defines two tags for time: CBOR tag 0 (RFC 3339 time as a
string) and tag 1 (POSIX time as int or float). Since then, string) and tag 1 (POSIX time as int or float). Since then,
additional requirements have become known. The present document additional requirements have become known. The present document
defines a CBOR tag for time that allows a more elaborate defines a CBOR tag for time that allows a more elaborate
representation of time, as well as related CBOR tags for duration and representation of time, as well as related CBOR tags for duration and
time period. This document is intended as the reference document for time period. This document is intended as the reference document for
the IANA registration of the CBOR tags defined. the IANA registration of the CBOR tags defined.
// (This cref will be removed by the RFC editor:) The present
// revision (–12) addresses the IESG reviews.
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-cbor-time-tag/.
Discussion of this document takes place on the CBOR Working Group
mailing list (mailto:cbor@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/cbor/. Subscribe at
https://www.ietf.org/mailman/listinfo/cbor/.
Source for this draft and an issue tracker can be found at
https://github.com/cbor-wg/time-tag.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
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 This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on 2 May 2024. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9581.
Copyright Notice Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/ Provisions Relating to IETF Documents
license-info) in effect on the date of publication of this document. (https://trustee.ietf.org/license-info) in effect on the date of
Please review these documents carefully, as they describe your rights publication of this document. Please review these documents
and restrictions with respect to this document. Code Components carefully, as they describe your rights and restrictions with respect
extracted from this document must include Revised BSD License text as to this document. Code Components extracted from this document must
described in Section 4.e of the Trust Legal Provisions and are include Revised BSD License text as described in Section 4.e of the
provided without warranty as described in the Revised BSD License. Trust Legal Provisions and are provided without warranty as described
in the Revised BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology
2. Objectives . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Objectives
3. Time Format . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Time Format
3.1. Key 1 . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1. Key 1
3.2. Keys 4 and 5 . . . . . . . . . . . . . . . . . . . . . . 6 3.2. Keys 4 and 5
3.3. Keys -3, -6, -9, -12, -15, -18 . . . . . . . . . . . . . 7 3.3. Keys -3, -6, -9, -12, -15, and -18
3.4. Key -1: Timescale . . . . . . . . . . . . . . . . . . . . 8 3.4. Key -1: Timescale
3.5. Clock Quality . . . . . . . . . . . . . . . . . . . . . . 8 3.5. Clock Quality
3.5.1. ClockClass (Key -2) . . . . . . . . . . . . . . . . . 9 3.5.1. ClockClass (Key -2)
3.5.2. ClockAccuracy (Key -4) . . . . . . . . . . . . . . . 9 3.5.2. ClockAccuracy (Key -4)
3.5.3. OffsetScaledLogVariance (Key -5) . . . . . . . . . . 9 3.5.3. OffsetScaledLogVariance (Key -5)
3.5.4. Uncertainty (Key -7) . . . . . . . . . . . . . . . . 10 3.5.4. Uncertainty (Key -7)
3.5.5. Guarantee (Key -8) . . . . . . . . . . . . . . . . . 10 3.5.5. Guarantee (Key -8)
3.6. Keys -10, 10: Time Zone Hint . . . . . . . . . . . . . . 11 3.6. Keys -10, 10: Time Zone Hint
3.7. Keys -11, 11: IXDTF Suffix Information . . . . . . . . . 11 3.7. Keys -11, 11: IXDTF Suffix Information
4. Duration Format . . . . . . . . . . . . . . . . . . . . . . . 13 4. Duration Format
5. Period Format . . . . . . . . . . . . . . . . . . . . . . . . 13 5. Period Format
6. CDDL typenames . . . . . . . . . . . . . . . . . . . . . . . 14 6. CDDL Type Names
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 7. IANA Considerations
7.1. CBOR tags . . . . . . . . . . . . . . . . . . . . . . . . 15 7.1. CBOR Tags
7.2. Timescale Registry . . . . . . . . . . . . . . . . . . . 15 7.2. Timescales Registry
7.3. Time Tag Map Key Registry . . . . . . . . . . . . . . . . 16 7.3. Time Tag Map Keys Registry
8. Security Considerations . . . . . . . . . . . . . . . . . . . 18 8. Security Considerations
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 9. References
9.1. Normative References . . . . . . . . . . . . . . . . . . 18 9.1. Normative References
9.2. Informative References . . . . . . . . . . . . . . . . . 20 9.2. Informative References
Appendix A. Collected CDDL . . . . . . . . . . . . . . . . . . . 21 Appendix A. Collected CDDL
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 23 Acknowledgements
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 Authors' Addresses
1. Introduction 1. Introduction
The Concise Binary Object Representation (CBOR, [RFC8949]) provides The Concise Binary Object Representation (CBOR) [RFC8949] provides
for the interchange of structured data without a requirement for a for the interchange of structured data without a requirement for a
pre-agreed schema. RFC 8949 defines a basic set of data types, as pre-agreed schema. RFC 8949 defines a basic set of data types, as
well as a tagging mechanism that enables extending the set of data well as a tagging mechanism that enables extending the set of data
types supported via an IANA registry for CBOR tags (Section 9.2 of types supported via an IANA registry for CBOR tags (see
[RFC8949], [IANA.cbor-tags]). [IANA.cbor-tags] and Section 9.2 of [RFC8949]).
RFC 8949 defines two tags for time: CBOR tag 0 (RFC3339 time as a RFC 8949 defines two tags for time: CBOR tag 0 ([RFC3339] time as a
string) and tag 1 (POSIX time as int or float). Since then, string) and tag 1 (POSIX time as int or float). Since then,
additional requirements have become known. The present document additional requirements have become known. The present document
defines a CBOR tag for time that allows a more elaborate defines a CBOR tag for time that allows a more elaborate
representation of time, as well as related CBOR tags for duration and representation of time, as well as related CBOR tags for durations
time period. This document is intended as the reference document for and time periods. This document is intended as the reference
the IANA registration of the CBOR tags defined. document for the IANA registration of the CBOR tags defined.
1.1. Terminology 1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
The term "byte" is used in its now customary sense as a synonym for The term "byte" is used in its now customary sense as a synonym for
"octet". "octet".
Superscript notation denotes exponentiation. For example, 2 to the Superscript notation denotes exponentiation. For example, 2 to the
power of 64 is notated: 2^64. In the plain-text rendition of this power of 64 is notated: 2^64. In the plain-text rendition of this
specification, superscript notation is not available and specification, superscript notation is not available and
exponentiation therefore is rendered by the surrogate notation seen exponentiation is therefore rendered by the surrogate notation seen
here in the plain-text rendition. here in the plain-text rendition.
CBOR diagnostic notation is defined in Section 8 of [RFC8949] and CBOR diagnostic notation is defined in Section 8 of [RFC8949] and
Appendix G of [RFC8610]. A machine-processable model of the data Appendix G of [RFC8610]. A machine-processable model of the data
structures defined in this specification is provided throughout the structures defined in this specification is provided throughout the
text using the Concise Data Definition Language, CDDL [RFC8610]; text using the Concise Data Definition Language (CDDL) [RFC8610];
Appendix A provides the collected model information. Appendix A provides the collected model information.
Several time-related terms such as UTC and TAI are discussed in Several time-related terms, such as UTC and International Atomic Time
[IXDTF], which may be a useful companion document beyond its direct (TAI), are discussed in [RFC9557], which may be a useful companion
use in Sections 3.6 and 3.7. document beyond its direct use in Sections 3.6 and 3.7.
2. Objectives 2. Objectives
For the time tag, the present specification addresses the following For the time tag, the present specification addresses the following
objectives that go beyond the original tags 0 and 1 (defined in objectives that go beyond the original tags 0 and 1 (defined in
Sections 3.4.1 and 3.4.2 of [RFC8949]): Sections 3.4.1 and 3.4.2 of [RFC8949]):
* Additional resolution for epoch-based time (as in tag 1). CBOR * Additional resolution for epoch-based time (as in tag 1). CBOR
tag 1 only provides for integer and up to binary64 floating point tag 1 only provides for integer and up to binary64 floating point
representation of times, limiting resolution to approximately representation of times, limiting resolution to approximately
microseconds at the time of writing (and progressively becoming microseconds at the time of writing (and progressively becoming
worse over time). worse over time).
* Indication of timescale. Tags 0 and 1 are defined for UTC; * Indication of timescale. Tags 0 and 1 are defined for UTC;
however, some interchanges are better performed on TAI. Other however, some interchanges are better performed on TAI. Other
timescales may be registered once they become relevant (e.g., one timescales may be registered once they become relevant (e.g., one
of the proposed successors to UTC that might no longer use leap of the proposed successors to UTC that might no longer use leap
seconds, or a scale based on smeared leap seconds). seconds or a scale based on smeared leap seconds).
By incorporating a way to transport [IXDTF] suffix information By incorporating a way to transport [RFC9557] suffix information (see
(Section 3.6, Section 3.7), additional indications can be provided of Sections 3.6 and 3.7), additional indications of intents about the
intents about the interpretation of the time given, in particular interpretation of the time given can be provided; in particular, for
also for instances of time that, at the time they are being instances of time that, at the time they are being described, are in
described, are in the future. Intents might include information the future. Intents might include information about time zones,
about time zones, daylight savings times, preferred calendar daylight saving times, preferred calendar representations, etc.
representations, etc.
Semantics not covered by this document can be added by registering Semantics not covered by this document can be added by registering
additional map keys for the map that is the content of the tag (see additional map keys for the map that is the content of the tag (see
etime-detailed in Figure 1), the specification for which is etime-detailed in Figure 1), the specification for which is
referenced by the registry entry (see Section 3). referenced by the registry entry (see Section 3).
For example, map keys could be registered for direct representations For example, map keys could be registered for direct representations
of natural platform time formats. Some platforms use epoch-based of natural platform time formats. Some platforms use epoch-based
time formats that require some computation to convert them into the time formats that require some computation to convert them into the
representations allowed by tag 1; these computations can also lose representations allowed by tag 1; these computations can also lose
precision and cause ambiguities. (The present specification does not precision and cause ambiguities. (The present specification does not
take a position on whether tag 1 can be "fixed" to include, e.g., take a position on whether tag 1 can be "fixed" to include, e.g.,
Decimal or BigFloat representations. It does define how to use these Decimal or Bigfloat representations. It does define how to use these
representations with the extended time format.) representations with the extended time format.)
Additional tags are defined for durations and periods. Additional tags are defined for durations and periods.
3. Time Format 3. Time Format
An extended time is indicated by CBOR tag 1001, the content of which An extended time is indicated by CBOR tag 1001, the content of which
is a map data item (CBOR major type 5). The map may contain integer is a map data item (CBOR major type 5). The map may contain integer
(major types 0 and 1) or text string (major type 3) keys, with the (major types 0 and 1) or text string (major type 3) keys, with the
value type determined by each specific key. For negative integer value type determined by each specific key. For negative integer
keys and text string values of the key, implementations MUST ignore keys and text string values of the key, implementations MUST ignore
key/value pairs they do not understand; these keys are "elective", as key/value pairs they do not understand; these keys are "elective", as
the extended time as a whole is still usable without the information the extended time as a whole is still usable without the information
they carry if an implementation elects not to implement them. they carry if an implementation elects not to implement them.
Conversely, for unsigned integer keys, implementations MUST signal as Conversely, for unsigned integer keys, implementations MUST signal as
an error key/value pairs they do not understand or implement (these an error key/value pairs they do not understand or implement (these
are either "base time" or "critical", see below). are either "base time" or "critical", see below).
The map MUST contain exactly one unsigned integer key that specifies The map MUST contain exactly one unsigned integer key that specifies
the "base time", and MAY also contain one or more negative integer or the "base time" and MAY also contain one or more negative integer or
text-string keys, which may encode supplementary information. text-string keys, which may encode supplementary information.
Supplementary information MAY also be provided by additional unsigned Supplementary information MAY also be provided by additional unsigned
integer keys that are explicitly defined to provide supplementary integer keys that are explicitly defined to provide supplementary
information (we say these keys are defined to be "critical"); as information (we say these keys are defined to be "critical"); as
these are required to be understood, there can be no confusion with these are required to be understood, there can be no confusion with
base time keys. base time keys.
Negative integer and text string keys always supply supplementary Negative integer and text string keys always supply supplementary
information (they are "elective", and this will not be explicitly information (they are "elective", and this will not be explicitly
stated below). stated below).
Supplementary information may include: Supplementary information may include:
* a higher precision time offset to be added to the base time, * a higher precision time offset to be added to the base time,
* a reference timescale and epoch different from the default UTC and * a reference timescale and epoch different from the default UTC and
1970-01-01 1970-01-01, and
* information about clock quality parameters, such as source, * information about clock quality parameters, such as source,
accuracy, and uncertainty accuracy, and uncertainty.
Additional keys can be defined by registering them in the Map Key Additional keys can be defined by registering them in the "Time Tag
Registry (Section 7.3). Registered keys may, for instance, add Map Keys" registry (Section 7.3). Registered keys may, for instance,
intent information such as timezone and daylight savings time, and/or add intent information such as time zone, daylight saving time, and/
possibly positioning coordinates, to express information that would or possibly positioning coordinates to express information that would
indicate a local time. indicate a local time.
This document does not define supplementary text keys. A number of This document does not define supplementary text keys. A number of
both unsigned and negative-integer keys are defined in the following both unsigned and negative-integer keys are defined in the following
subsections. subsections.
Figure 1 provides a formal definition of Tag 1001 in CDDL. Figure 1 provides a formal definition of Tag 1001 in CDDL.
Etime = #6.1001(etime-detailed) Etime = #6.1001(etime-detailed)
skipping to change at page 6, line 34 skipping to change at line 243
etime-detailed = ({ etime-detailed = ({
$$ETIME-BASETIME $$ETIME-BASETIME
ClockQuality-group ClockQuality-group
* $$ETIME-ELECTIVE * $$ETIME-ELECTIVE
* $$ETIME-CRITICAL * $$ETIME-CRITICAL
* ((nint/text) .feature "etime-elective-extension") => any * ((nint/text) .feature "etime-elective-extension") => any
* (uint .feature "etime-critical-extension") => any * (uint .feature "etime-critical-extension") => any
}) .within etime-framework }) .within etime-framework
Figure 1: CDDL definition of Tag 1001 Figure 1: CDDL Definition of Tag 1001
3.1. Key 1 3.1. Key 1
Key 1 indicates a base time value that is exactly like the data item Key 1 indicates a base time value that is exactly like the data item
that would be tagged by CBOR tag 1 (POSIX time [TIME_T] as int or that would be tagged by CBOR tag 1 (POSIX time [TIME_T] as int or
float). As described above, the time value indicated by the value float). As described above, the time value indicated by the value
under this key can be further modified by other keys. under this key can be further modified by other keys.
$$ETIME-BASETIME //= (1: ~time) $$ETIME-BASETIME //= (1: ~time)
skipping to change at page 7, line 8 skipping to change at line 265
Keys 4 and 5 indicate a base time value and are like key 1, except Keys 4 and 5 indicate a base time value and are like key 1, except
that the data item is an array as defined for CBOR tag 4 or 5, that the data item is an array as defined for CBOR tag 4 or 5,
respectively. This can be used to include a Decimal or Bigfloat respectively. This can be used to include a Decimal or Bigfloat
epoch-based float [TIME_T] in an extended time, e.g., to achieve epoch-based float [TIME_T] in an extended time, e.g., to achieve
higher resolution or to avoid rounding errors. higher resolution or to avoid rounding errors.
$$ETIME-BASETIME //= (4: ~decfrac) $$ETIME-BASETIME //= (4: ~decfrac)
$$ETIME-BASETIME //= (5: ~bigfloat) $$ETIME-BASETIME //= (5: ~bigfloat)
3.3. Keys -3, -6, -9, -12, -15, -18 3.3. Keys -3, -6, -9, -12, -15, and -18
The keys -3, -6, -9, -12, -15 and -18 indicate additional decimal The keys -3, -6, -9, -12, -15, and -18 indicate additional decimal
fractions by giving an unsigned integer (major type 0) and scaling fractions by giving an unsigned integer (major type 0) and scaling
this with the scale factor 1e-3, 1e-6, 1e-9, 1e-12, 1e-15, and 1e-18, this with the scale factor 1e-3, 1e-6, 1e-9, 1e-12, 1e-15, and 1e-18,
respectively (see Table 1). Each extended time data item MUST NOT respectively (see Table 1). Each extended time data item MUST NOT
contain more than one of these keys. These additional fractions are contain more than one of these keys. These additional fractions are
added to a base time in seconds [SI-SECOND] indicated by a Key 1, added to a base time in seconds [SI-SECOND] indicated by Key 1, which
which then MUST also be present and MUST have an integer value. then MUST also be present and MUST have an integer value.
+=====+==============+=================+ +=====+==============+=================+
| Key | meaning | example usage | | Key | Meaning | Example Usage |
+=====+==============+=================+ +=====+==============+=================+
| -3 | milliseconds | Java time | | -3 | milliseconds | Java time |
+-----+--------------+-----------------+ +-----+--------------+-----------------+
| -6 | microseconds | (old) UNIX time | | -6 | microseconds | (old) UNIX time |
+-----+--------------+-----------------+ +-----+--------------+-----------------+
| -9 | nanoseconds | (new) UNIX time | | -9 | nanoseconds | (new) UNIX time |
+-----+--------------+-----------------+ +-----+--------------+-----------------+
| -12 | picoseconds | Haskell time | | -12 | picoseconds | Haskell time |
+-----+--------------+-----------------+ +-----+--------------+-----------------+
| -15 | femtoseconds | (future) | | -15 | femtoseconds | (future) |
+-----+--------------+-----------------+ +-----+--------------+-----------------+
| -18 | attoseconds | (future) | | -18 | attoseconds | (future) |
+-----+--------------+-----------------+ +-----+--------------+-----------------+
Table 1: Key for decimally scaled Table 1: Keys for Decimally Scaled
Fractions Fractions
$$ETIME-ELECTIVE //= (-3: uint) $$ETIME-ELECTIVE //= (-3: uint)
$$ETIME-ELECTIVE //= (-6: uint) $$ETIME-ELECTIVE //= (-6: uint)
$$ETIME-ELECTIVE //= (-9: uint) $$ETIME-ELECTIVE //= (-9: uint)
$$ETIME-ELECTIVE //= (-12: uint) $$ETIME-ELECTIVE //= (-12: uint)
$$ETIME-ELECTIVE //= (-15: uint) $$ETIME-ELECTIVE //= (-15: uint)
$$ETIME-ELECTIVE //= (-18: uint) $$ETIME-ELECTIVE //= (-18: uint)
Note that these keys have been provided to facilitate representing Note that these keys have been provided to facilitate representing
pairs of the form second/decimal fraction of a second, as found for pairs of the form second/decimal fraction of a second, as found for
instance in C timespec (Section 7.27.1 of [C]). When ingesting a instance in C timespec (Section 7.27.1 of [C]). When ingesting a
timestamp with one of these keys into a type provided by the target timestamp with one of these keys into a type provided by the target
platform, care has to be taken to meet its invariants. E.g., for C platform, care has to be taken to meet its invariants. For example,
timespec, the fractional part tv_nsec needs to be between 0 inclusive for C timespec, the fractional part tv_nsec needs to be between 0
and 10^9 exclusive, which can be achieved by also adjusting the base inclusive and 10^9 exclusive, which can be achieved by also adjusting
time appropriately. the base time appropriately.
3.4. Key -1: Timescale 3.4. Key -1: Timescale
Key -1 is used to indicate a timescale. The value 0 indicates UTC, Key -1 is used to indicate a timescale. The value 0 indicates UTC,
with the POSIX epoch [TIME_T]; the value 1 indicates TAI, with the with the POSIX epoch [TIME_T]; the value 1 indicates TAI, with the
PTP (Precision Time Protocol) epoch (1 January 1970 00:00:00 TAI, see Precision Time Protocol (PTP) epoch (1 January 1970 00:00:00 TAI, see
[IEEE1588-2019] or [IEEE1588-2008]). [IEEE1588-2019] or [IEEE1588-2008]).
$$ETIME-ELECTIVE //= (-1 => $ETIME-TIMESCALE) $$ETIME-ELECTIVE //= (-1 => $ETIME-TIMESCALE)
$ETIME-TIMESCALE /= &(etime-utc: 0) $ETIME-TIMESCALE /= &(etime-utc: 0)
$ETIME-TIMESCALE /= &(etime-tai: 1) $ETIME-TIMESCALE /= &(etime-tai: 1)
If key -1 is not present, the default timescale value 0 is implied. If key -1 is not present, the default timescale value 0 is implied.
Timescale values MUST be unsigned integers or text strings; text Timescale values MUST be unsigned integers or text strings; text
strings are provided for experimentation and MUST NOT be used between strings are provided for experimentation and MUST NOT be used between
parties which are not both part of the experiment. Additional parties that are not both part of the experiment. Additional
unsigned integer values can be registered in the Timescale Registry unsigned integer values can be registered in the "Timescales"
(Section 7.2). (Note that there should be no timescales "GPS" or registry (Section 7.2). (Note that there should be no timescales
"NTP" [RFC5905] — instead, the time should be converted to TAI or UTC "GPS" or "NTP" [RFC5905] -- instead, the time should be converted to
using a single addition or subtraction.) TAI or UTC using a single addition or subtraction.)
t = t - 2208988800 t = t - 2208988800
utc ntp utc ntp
t = t + 315964819 t = t + 315964819
tai gps tai gps
Figure 2: Converting Common Offset Timescales Figure 2: Converting Common Offset Timescales
| Editor's note: This initial set of timescales was deliberately | Editor's note: This initial set of timescales was deliberately
| chosen to be frugal, as the specification of the tag provides | chosen to be frugal, as the specification of the tag provides
| an extension point where additional timescales can be | an extension point where additional timescales can be
| registered at any time. Registrations are clearly needed for | registered at any time. Registrations are clearly needed for
| earth-referenced timescales (such as UT1 and TT), as well as | earth-referenced timescales (such as UT1 and TT), as well as
| possibly for specific realizations of abstract time scales | possibly for specific realizations of abstract timescales (such
| (such as TAI(USNO) which is more accurate as a constant offset | as TAI (United States Naval Observatory (USNO)), which is more
| basis for GPS times). While the registration process itself is | accurate as a constant offset basis for GPS times). While the
| trivial, these registrations need to be made based on a solid | registration process itself is trivial, these registrations
| specification of their actual definition. | need to be made based on a solid specification of their actual
| definition.
3.5. Clock Quality 3.5. Clock Quality
A number of keys are defined to indicate the quality of clock that A number of keys are defined to indicate the quality of clock that
was used to determine the point in time. was used to determine the point in time.
The first three are analogous to clock-quality-grouping in [RFC8575], The first three are analogous to clock-quality-grouping in [RFC8575],
which is in turn based on the definitions in [IEEE1588-2008]; the which is in turn based on the definitions in [IEEE1588-2008]; the
last two are specific to this document. last two are specific to this document.
skipping to change at page 9, line 33 skipping to change at line 385
that is the range defined in IEEE 1588. that is the range defined in IEEE 1588.
3.5.2. ClockAccuracy (Key -4) 3.5.2. ClockAccuracy (Key -4)
Key -4 (ClockAccuracy) can be used to indicate the clock accuracy as Key -4 (ClockAccuracy) can be used to indicate the clock accuracy as
per [RFC8575] (which is based on Table 6 in Section 7.6.2.5 of per [RFC8575] (which is based on Table 6 in Section 7.6.2.5 of
[IEEE1588-2008]; additional values have been defined in Table 5 in [IEEE1588-2008]; additional values have been defined in Table 5 in
Section 7.6.2.6 of [IEEE1588-2019]). It is defined as a one-byte Section 7.6.2.6 of [IEEE1588-2019]). It is defined as a one-byte
unsigned integer as that is the range defined there. The range unsigned integer as that is the range defined there. The range
between 23 and 47 is a slightly distorted logarithmic scale from 1 ps between 23 and 47 is a slightly distorted logarithmic scale from 1 ps
to 1 s in [IEEE1588-2019] (in [IEEE1588-2008] the range was a subset to 1 s in [IEEE1588-2019] (in [IEEE1588-2008], the range was a subset
of that, 32 to 47 for 25 ns to 1 s) — see Figure 3; the number 254 is of that, 32 to 47 for 25 ns to 1 s) -- see Figure 3; the number 254
the value to be used if an unknown accuracy needs to be expressed. is the value to be used if an unknown accuracy needs to be expressed.
acc acc
enum ≈ 48 + ⌊2 ⋅log ──── - ε⌋ enum ≈ 48 + ⌊2 ⋅log ──── - ε⌋
acc 10 s acc 10 s
Figure 3: Approximate conversion from accuracy to accuracy Figure 3: Approximate Conversion from Accuracy to Accuracy
enumeration value Enumeration Value
3.5.3. OffsetScaledLogVariance (Key -5) 3.5.3. OffsetScaledLogVariance (Key -5)
Key -5 (OffsetScaledLogVariance) can be used to represent the Key -5 (OffsetScaledLogVariance) can be used to represent the
variance exhibited by the clock when it has lost its synchronization variance exhibited by the clock when it has lost its synchronization
with an external reference clock. The details for the computation of with an external reference clock. The details for the computation of
this characteristic are defined in Section 7.6.3 of [IEEE1588-2019] this characteristic are defined in Section 7.6.3 of [IEEE1588-2019]
and the same section in [IEEE1588-2008]. and the same section in [IEEE1588-2008].
3.5.4. Uncertainty (Key -7) 3.5.4. Uncertainty (Key -7)
Key -7 (Uncertainty) can be used to represent a known measurement Key -7 (Uncertainty) can be used to represent a known measurement of
uncertainty for the clock, as a numeric value in seconds or as a uncertainty for the clock as a numeric value in seconds or as a
duration (Section 4). duration (Section 4).
For this document, uncertainty is defined as in Section 2.2.3 of For this document, uncertainty is defined as in Section 2.2.3 of
[GUM]: "parameter, associated with the result of a measurement, that [GUM]: "parameter, associated with the result of a measurement, that
characterizes the dispersion of the values that could reasonably be characterizes the dispersion of the values that could reasonably be
attributed to the measurand". More specifically, the value for this attributed to the measurand". More specifically, the value for this
key represents the expanded uncertainty for k = 2 (Section 6.2.1 of key represents the expanded uncertainty for k = 2 (Section 6.2.1 of
[GUM]), in seconds. [GUM]) in seconds.
Note that the additional information that can be meaningfully Note that the additional information that can be meaningfully
provided with the duration that represents an uncertainty is limited, provided with the duration that represents an uncertainty is limited,
e.g., it is not customary to provide an uncertainty for a duration e.g., it is not customary to provide an uncertainty for a duration
representing an uncertainty. Implementations are free to reduce the representing an uncertainty. Implementations are free to reduce the
information contained in an uncertainty (which is already elective) information contained in an uncertainty (which is already elective)
to the information they can process. to the information they can process.
For example, a timestamp that is given to a resolution of 10^-6 For example, a timestamp that is given to a resolution of 10^-6
seconds (microseconds) but only has an uncertainty of 10^-3 seconds seconds (microseconds) but only has an uncertainty of 10^-3 seconds
skipping to change at page 10, line 40 skipping to change at line 439
1001({1: 1697724754, -6: 873294, -7: {1: 0, -6: 1000}}), 1001({1: 1697724754, -6: 873294, -7: {1: 0, -6: 1000}}),
1001({1: 1697724754, -6: 873294, -7: {1: 0, -3: 1}}), 1001({1: 1697724754, -6: 873294, -7: {1: 0, -3: 1}}),
1001({1: 1697724754, -6: 873294, -7: {1: 0.001}}) 1001({1: 1697724754, -6: 873294, -7: {1: 0.001}})
Figure 4: Examples Using Uncertainty Figure 4: Examples Using Uncertainty
3.5.5. Guarantee (Key -8) 3.5.5. Guarantee (Key -8)
Key -8 (Guarantee) can be used to represent a stated guarantee for Key -8 (Guarantee) can be used to represent a stated guarantee for
the accuracy of the point in time, as a numeric value in seconds or the accuracy of the point in time as a numeric value in seconds or as
as a duration (Section 4) representing the maximum allowed deviation a duration (Section 4) representing the maximum allowed deviation
from the true value. from the true value.
While such a guarantee is unattainable in theory, existing standards While such a guarantee is unattainable in theory, existing standards
such as [RFC3161] stipulate the representation of such guarantees, such as [RFC3161] stipulate the representation of such guarantees,
and therefore this format provides a way to represent them as well; and therefore this format provides a way to represent them as well;
the time value given is nominally guaranteed to not deviate from the the time value given is nominally guaranteed to not deviate from the
actual time by more than the value of the guarantee, in seconds. actual time by more than the value of the guarantee in seconds.
Note that the additional information that can be meaningfully Note that the additional information that can be meaningfully
provided with the duration that represents a guarantee is limited, provided with the duration that represents a guarantee is limited,
e.g., it is not meaningful to provide a guarantee of accuracy for the e.g., it is not meaningful to provide a guarantee of accuracy for the
duration representing a guarantee of accuracy. Implementations are duration representing a guarantee of accuracy. Implementations are
free to reduce a guarantee (which is already elective) to the free to reduce a guarantee (which is already elective) to the
information they can process. information they can process.
3.6. Keys -10, 10: Time Zone Hint 3.6. Keys -10, 10: Time Zone Hint
Keys -10 and 10 supply supplementary information, where key 10 is Keys -10 and 10 supply supplementary information, where key 10 is
critical. critical.
They can be used to provide a hint about the time zone that would They can be used to provide a hint about the time zone that would
best fit for displaying the time given to humans, using a text string best fit for displaying the time given to humans, using a text string
in the format defined for time-zone-name or time-numoffset in in the format defined for time-zone-name or time-numoffset in
[IXDTF]. Key -10 is equivalent to providing this information as an [RFC9557]. Key -10 is equivalent to providing this information as an
elective hint, while key 10 provides this information as critical elective hint, while key 10 provides this information as critical
(i.e., it MUST be used when interpreting the entry with this key). (i.e., it MUST be used when interpreting the entry with this key).
Keys -10 and 10 MUST NOT both be present. Keys -10 and 10 MUST NOT both be present.
$$ETIME-ELECTIVE //= (-10: time-zone-info) $$ETIME-ELECTIVE //= (-10: time-zone-info)
$$ETIME-CRITICAL //= (10: time-zone-info) $$ETIME-CRITICAL //= (10: time-zone-info)
time-zone-info = tstr .abnf time-zone-info = tstr .abnf
("time-zone-name / time-numoffset" .det IXDTFtz) ("time-zone-name / time-numoffset" .det IXDTFtz)
skipping to change at page 11, line 39 skipping to change at line 487
time-minute = 2DIGIT ; 00-59 time-minute = 2DIGIT ; 00-59
time-numoffset = ("+" / "-") time-hour ":" time-minute time-numoffset = ("+" / "-") time-hour ":" time-minute
time-zone-initial = ALPHA / "." / "_" time-zone-initial = ALPHA / "." / "_"
time-zone-char = time-zone-initial / DIGIT / "-" / "+" time-zone-char = time-zone-initial / DIGIT / "-" / "+"
time-zone-part = time-zone-initial *13(time-zone-char) time-zone-part = time-zone-initial *13(time-zone-char)
; but not "." or ".." ; but not "." or ".."
time-zone-name = time-zone-part *("/" time-zone-part) time-zone-name = time-zone-part *("/" time-zone-part)
ALPHA = %x41-5A / %x61-7A ; A-Z / a-z ALPHA = %x41-5A / %x61-7A ; A-Z / a-z
DIGIT = %x30-39 ; 0-9 DIGIT = %x30-39 ; 0-9
' ; extracted from [IXDTF] and [RFC3339]; update as needed ' ; extracted from [RFC9557] and [RFC3339]; update as needed
3.7. Keys -11, 11: IXDTF Suffix Information 3.7. Keys -11, 11: IXDTF Suffix Information
Keys -11 and 11 supply supplementary information, where key 11 is Keys -11 and 11 supply supplementary information, where key 11 is
critical. critical.
Similar to keys -10 and 10, keys -11 (elective) and 11 (critical) can Similar to keys -10 and 10, keys -11 (elective) and 11 (critical) can
be used to provide additional information in the style of IXDTF be used to provide additional information in the style of Internet
suffixes, such as the calendar that would best fit for displaying the Extended Date/Time Format (IXDTF) suffixes, such as the calendar that
time given to humans. The key's value is a map that has IXDTF would best fit for displaying the time given to humans. The key's
suffix-key names as keys and corresponding suffix values as values, value is a map that has IXDTF suffix-key names as keys and
specifically: corresponding suffix values as values, specifically:
$$ETIME-ELECTIVE //= (-11: suffix-info-map) $$ETIME-ELECTIVE //= (-11: suffix-info-map)
$$ETIME-CRITICAL //= (11: suffix-info-map) $$ETIME-CRITICAL //= (11: suffix-info-map)
suffix-info-map = { * suffix-key => suffix-values } suffix-info-map = { * suffix-key => suffix-values }
suffix-key = tstr .abnf ("suffix-key" .det IXDTF) suffix-key = tstr .abnf ("suffix-key" .det IXDTF)
suffix-values = one-or-more<suffix-value> suffix-values = one-or-more<suffix-value>
one-or-more<T> = T / [ 2* T ] one-or-more<T> = T / [ 2* T ]
suffix-value = tstr .abnf ("suffix-value" .det IXDTF) suffix-value = tstr .abnf ("suffix-value" .det IXDTF)
IXDTF = ' IXDTF = '
key-initial = lcalpha / "_" key-initial = lcalpha / "_"
key-char = key-initial / DIGIT / "-" key-char = key-initial / DIGIT / "-"
suffix-key = key-initial *key-char suffix-key = key-initial *key-char
suffix-value = 1*alphanum suffix-value = 1*alphanum
alphanum = ALPHA / DIGIT alphanum = ALPHA / DIGIT
lcalpha = %x61-7A lcalpha = %x61-7A
ALPHA = %x41-5A / %x61-7A ; A-Z / a-z ALPHA = %x41-5A / %x61-7A ; A-Z / a-z
DIGIT = %x30-39 ; 0-9 DIGIT = %x30-39 ; 0-9
' ; extracted from [IXDTF]; update as needed! ' ; extracted from [RFC9557]; update as needed!
When keys -11 and 11 both are present, the two maps MUST NOT have When keys -11 and 11 are both present, the two maps MUST NOT have
entries with the same map keys. entries with the same map keys.
Figure 4 of [IXDTF] gives an example for an extended date-time with Figure 4 of [RFC9557] gives an example for an extended date-time with
both time zone and suffix information: both time zone and suffix information:
1996-12-19T16:39:57-08:00[America/Los_Angeles][u-ca=hebrew] 1996-12-19T16:39:57-08:00[America/Los_Angeles][u-ca=hebrew]
A time tag that is approximating this example, in CBOR diagnostic A time tag that is approximating this example, in CBOR diagnostic
notation, would be: notation, would be:
/ 1996-12-19T16:39:57-08:00[America//Los_Angeles][u-ca=hebrew] / / 1996-12-19T16:39:57-08:00[America//Los_Angeles][u-ca=hebrew] /
1001({ 1: 851042397, 1001({ 1: 851042397,
-10: "America/Los_Angeles", -10: "America/Los_Angeles",
-11: { "u-ca": "hebrew" } -11: { "u-ca": "hebrew" }
}) })
Note that both -10 and -11 are using negative keys and therefore Note that both -10 and -11 are using negative keys and therefore
provide elective information, as in the IXDTF form given in the provide elective information, as in the IXDTF form given in the
comment. Note also that in this example the time numeric offset comment. Also note that, in this example, the time numeric offset
(-08:00) is lost in translating from the [RFC3339] information in the (-08:00) is lost in translating from the [RFC3339] information in the
IXDTF into a POSIX time that can be included under Key 1 in a time IXDTF into a POSIX time that can be included under Key 1 in a time
tag. tag.
4. Duration Format 4. Duration Format
A duration is the length of an interval of time. Durations in this A duration is the length of an interval of time. Durations in this
format are given in SI seconds, possibly adjusted for conventional format are given in International System of Units (SI) seconds,
corrections of the timescale given (e.g., leap seconds). possibly adjusted for conventional corrections of the timescale given
(e.g., leap seconds).
Except for using Tag 1002 instead of 1001, durations are structurally Except for using Tag 1002 instead of 1001, durations are structurally
identical to time values. identical to time values.
Duration = #6.1002(etime-detailed) Duration = #6.1002(etime-detailed)
Semantically, they do not measure the time elapsed from a given Semantically, they do not measure the time elapsed from a given epoch
epoch, but from the start to the end of (an otherwise unspecified) but from the start to the end of an (otherwise unspecified) interval
interval of time. of time.
In combination with an epoch identified in the context, a duration In combination with an epoch identified in the context, a duration
can also be used to express an absolute time. can also be used to express an absolute time.
Without such context, durations are subject to some uncertainties Without such context, durations are subject to some uncertainties
underlying the timescale used. E.g., for durations intended as a underlying the timescale used. For example, for durations intended
determinant of future time periods, there is some uncertainty of what as a determinant of future time periods, there is some uncertainty of
irregularities (such as leap seconds, timescale corrections) will be what irregularities (such as leap seconds and timescale corrections)
exhibited by the timescale in that period. For durations as will be exhibited by the timescale in that period. For durations as
measurements of past periods, abstracting the period to a duration measurements of past periods, abstracting the period to a duration
loses some detail about timescale irregularities. For many loses some detail about timescale irregularities. For many
applications, these uncertainties are acceptable and thus the use of applications, these uncertainties are acceptable and thus the use of
durations is appropriate. durations is appropriate.
| Note that the durations defined in [ISO8601:1988] and | Note that the durations defined in [ISO8601:1988] and
| [ISO8601-1:2019] are rather different from the ones defined in | [ISO8601-1:2019] are rather different from the ones defined in
| the present specification; there is no intention to support ISO | the present specification; there is no intention to support ISO
| 8601 durations here. | 8601 durations here.
5. Period Format 5. Period Format
A period is a specific interval of time, specified as either two A period is a specific interval of time, specified as either two
extended times giving the start and the end of that interval, or as extended times giving the start and the end of that interval or as
one of these two plus a duration. one of these two plus a duration.
This is represented as an array of unwrapped time and duration This is represented as an array of unwrapped time and duration
elements, tagged with Tag 1003, one of: elements, tagged with Tag 1003, one of:
* a start and end time, in which case the tag content is an array of * a start and end time, in which case the tag content is an array of
two unwrapped extended time elements; two unwrapped extended time elements, or
* a start time with duration or an end time with duration. The tag * a start time with duration or an end time with duration. The tag
content is an array of 3 elements: the first two as above but content is an array of 3 elements: the first two as above but
either the start or end time MUST be set to null; the third one either the start or end time MUST be set to null and the third one
then is an unwrapped duration. then is an unwrapped duration.
A simple CDDL definition that does not capture all the constraints A simple CDDL definition that does not capture all the constraints
is: is:
simple-Period = #6.1003([ simple-Period = #6.1003([
start: ~Etime / null start: ~Etime / null
end: ~Etime / null end: ~Etime / null
? duration: ~Duration ? duration: ~Duration
]) ])
skipping to change at page 14, line 32 skipping to change at line 619
Period = #6.1003([ Period = #6.1003([
(start: ~Etime, (start: ~Etime,
((end: ~Etime) // ((end: ~Etime) //
(end: null, (end: null,
duration: ~Duration))) // duration: ~Duration))) //
(start: null, (start: null,
end: ~Etime, end: ~Etime,
duration: ~Duration) duration: ~Duration)
]) ])
6. CDDL typenames 6. CDDL Type Names
When detailed validation is not needed, the type names defined in When detailed validation is not needed, the type names defined in
Figure 5 are recommended: Figure 5 are recommended:
etime = #6.1001({* (int/tstr) => any}) etime = #6.1001({* (int/tstr) => any})
duration = #6.1002({* (int/tstr) => any}) duration = #6.1002({* (int/tstr) => any})
period = #6.1003([~etime/null, ~etime/null, ~duration/null]) period = #6.1003([~etime/null, ~etime/null, ~duration/null])
Figure 5: Recommended type names for CDDL Figure 5: Recommended Type Names for CDDL
7. IANA Considerations 7. IANA Considerations
// RFC Editor: please replace RFCthis with the RFC number of this 7.1. CBOR Tags
// RFC, and remove this note.
7.1. CBOR tags
In the "CBOR Tags" registry [IANA.cbor-tags], IANA has allocated the In the "CBOR Tags" registry [IANA.cbor-tags], IANA has allocated the
tags in Table 2 from what was at the time the FCFS space, with the tags in Table 2 out of the First Come First Served (FCFS) range and
present document as the specification reference. listed this document as the specification reference.
+======+===========+=========================+ +======+===========+=========================+
| Tag | Data Item | Semantics | | Tag | Data Item | Semantics |
+======+===========+=========================+ +======+===========+=========================+
| 1001 | map | [RFCthis] extended time | | 1001 | map | [RFC9581] extended time |
+------+-----------+-------------------------+ +------+-----------+-------------------------+
| 1002 | map | [RFCthis] duration | | 1002 | map | [RFC9581] duration |
+------+-----------+-------------------------+ +------+-----------+-------------------------+
| 1003 | array | [RFCthis] period | | 1003 | array | [RFC9581] period |
+------+-----------+-------------------------+ +------+-----------+-------------------------+
Table 2: Values for Tags Table 2: Values for Tags
IANA is requested to change the "Data Item" column for Tag 1003 from IANA has updated the "Data Item" column for Tag 1003 from "map" to
"map" to "array". "array".
7.2. Timescale Registry 7.2. Timescales Registry
This specification defines a new registry titled "Timescales" in the Per this specification, IANA has created a new "Timescales" registry
"CBOR Tags" registry group [IANA.cbor-tags], with a Registration within the "Concise Binary Object Representation (CBOR) Tags"
Procedure requiring both "Expert Review" and "RFC Required" (Sections registry group [IANA.cbor-tags]. The registration procedure is both
4.5 and 4.7 of [BCP26]). "Expert Review" and "RFC Required" (Sections 4.5 and 4.7 of RFC 8126
[BCP26], respectively).
Each entry needs to provide a timescale name (a sequence of uppercase Each entry needs to provide a timescale name (a sequence of uppercase
ASCII characters and digits, where a digit may not occur at the ASCII characters and digits, where a digit may not occur at the
start: [A-Z][A-Z0-9]*), a value (CBOR unsigned integer, uint, start: [A-Z][A-Z0-9]*), a value (CBOR unsigned integer, uint,
0..18446744073709551615), a brief description of the semantics, and a 0..18446744073709551615), a brief description of the semantics, and a
specification reference (RFC). The initial contents are shown in specification reference (RFC). The initial contents are shown in
Table 3. Table 3.
+===========+=======+======================+===========+ +===========+=======+======================+===========+
| Timescale | Value | Semantics | Reference | | Timescale | Value | Semantics | Reference |
+===========+=======+======================+===========+ +===========+=======+======================+===========+
| UTC | 0 | UTC with POSIX Epoch | [RFCthis] | | UTC | 0 | UTC with POSIX Epoch | [RFC9581] |
+-----------+-------+----------------------+-----------+ +-----------+-------+----------------------+-----------+
| TAI | 1 | TAI with PTP Epoch | [RFCthis] | | TAI | 1 | TAI with PTP Epoch | [RFC9581] |
+-----------+-------+----------------------+-----------+ +-----------+-------+----------------------+-----------+
Table 3: Initial Content of Timescale Registry Table 3: Initial Content of Timescale Registry
7.3. Time Tag Map Key Registry 7.3. Time Tag Map Keys Registry
This specification defines a new registry titled "Time Tag Map Keys" Per this specification, IANA has created a new "Time Tag Map Keys"
in the "CBOR Tags" registry group [IANA.cbor-tags], with registry within the "Concise Binary Object Representation (CBOR)
"Specification Required" as the Registration Procedure (Section 4.6 Tags" registry group [IANA.cbor-tags]. The registration procedure is
of [BCP26]). "Specification Required" (Section 4.6 of RFC 8126 [BCP26]).
The designated expert is requested to assign the key values with the The designated expert is requested to assign the key values with the
shortest encodings (1+0 and 1+1 encoding) to registrations that are shortest encodings (1+0 and 1+1 encoding) to registrations that are
likely to enjoy wide use and can benefit from short encodings. likely to enjoy wide use and can benefit from short encodings.
Each entry needs to provide a map key value (CBOR integer, int, Each entry needs to provide a map key value (CBOR integer, int,
-18446744073709551616..18446744073709551615), a brief description of -18446744073709551616..18446744073709551615), a brief description of
the semantics, and a specification reference. Note that negative the semantics, and a specification reference. Note that negative
integers indicate an elective key, while unsigned integers indicate a integers indicate an elective key, while unsigned integers indicate a
key that either provides a base time or is critical. For the key that either provides a base time or is critical. For the
unsigned integers as keys, the choice of base time or critical needs unsigned integers as keys, the choice of base time or critical needs
to be indicated in the brief semantics description. (Elective map to be indicated in the brief semantics description. (Elective map
keys may be explicitly marked as such in the description, e.g., to keys may be explicitly marked as such in the description, e.g., to
distinguish them from critical keys.) distinguish them from critical keys.)
The initial contents are shown in Table 4. The initial contents are shown in Table 4.
+=======+=====================================+=====================+ +=======+=====================================+============+
| Value | Semantics | Reference | | Value | Semantics | Reference |
+=======+=====================================+=====================+ +=======+=====================================+============+
| -18 | attoseconds | [RFCthis] | | -18 | attoseconds | [RFC9581] |
+-------+-------------------------------------+---------------------+ +-------+-------------------------------------+------------+
| -15 | femtoseconds | [RFCthis] | | -15 | femtoseconds | [RFC9581] |
+-------+-------------------------------------+---------------------+ +-------+-------------------------------------+------------+
| -12 | picoseconds | [RFCthis] | | -12 | picoseconds | [RFC9581] |
+-------+-------------------------------------+---------------------+ +-------+-------------------------------------+------------+
| -11 | IXDTF Suffix Information (elective) | [RFCthis], [IXDTF] | | -11 | IXDTF Suffix Information (elective) | [RFC9581], |
+-------+-------------------------------------+---------------------+ | | | [RFC9557] |
| -10 | IXDTF Time Zone Hint (elective) | [RFCthis], [IXDTF] | +-------+-------------------------------------+------------+
+-------+-------------------------------------+---------------------+ | -10 | IXDTF Time Zone Hint (elective) | [RFC9581], |
| -9 | nanoseconds | [RFCthis] | | | | [RFC9557] |
+-------+-------------------------------------+---------------------+ +-------+-------------------------------------+------------+
| -8 | Guarantee | [RFCthis] | | -9 | nanoseconds | [RFC9581] |
+-------+-------------------------------------+---------------------+ +-------+-------------------------------------+------------+
| -7 | Uncertainty | [RFCthis] | | -8 | Guarantee | [RFC9581] |
+-------+-------------------------------------+---------------------+ +-------+-------------------------------------+------------+
| -6 | microseconds | [RFCthis] | | -7 | Uncertainty | [RFC9581] |
+-------+-------------------------------------+---------------------+ +-------+-------------------------------------+------------+
| -5 | Offset-Scaled Log Variance | [RFCthis] | | -6 | microseconds | [RFC9581] |
+-------+-------------------------------------+---------------------+ +-------+-------------------------------------+------------+
| -4 | Clock Accuracy | [RFCthis] | | -5 | Offset-Scaled Log Variance | [RFC9581] |
+-------+-------------------------------------+---------------------+ +-------+-------------------------------------+------------+
| -3 | milliseconds | [RFCthis] | | -4 | Clock Accuracy | [RFC9581] |
+-------+-------------------------------------+---------------------+ +-------+-------------------------------------+------------+
| -2 | Clock Class | [RFCthis] | | -3 | milliseconds | [RFC9581] |
+-------+-------------------------------------+---------------------+ +-------+-------------------------------------+------------+
| 1 | base time value as in CBOR Tag 1 | [RFC8949] | | -2 | Clock Class | [RFC9581] |
| | | [RFCthis] | +-------+-------------------------------------+------------+
+-------+-------------------------------------+---------------------+ | 1 | base time value as in CBOR Tag 1 | [RFC8949], |
| 4 | base time value as in CBOR Tag 4 | [RFC8949] | | | | [RFC9581] |
| | | [RFCthis] | +-------+-------------------------------------+------------+
+-------+-------------------------------------+---------------------+ | 4 | base time value as in CBOR Tag 4 | [RFC8949], |
| 5 | base time value as in CBOR Tag 5 | [RFC8949] | | | | [RFC9581] |
| | | [RFCthis] | +-------+-------------------------------------+------------+
+-------+-------------------------------------+---------------------+ | 5 | base time value as in CBOR Tag 5 | [RFC8949], |
| 10 | IXDTF Time Zone Hint (critical) | [RFCthis], [IXDTF] | | | | [RFC9581] |
+-------+-------------------------------------+---------------------+ +-------+-------------------------------------+------------+
| 11 | IXDTF Suffix Information (critical) | [RFCthis], [IXDTF] | | 10 | IXDTF Time Zone Hint (critical) | [RFC9557], |
+-------+-------------------------------------+---------------------+ | | | [RFC9581] |
+-------+-------------------------------------+------------+
| 11 | IXDTF Suffix Information (critical) | [RFC9557], |
| | | [RFC9581] |
+-------+-------------------------------------+------------+
Table 4: Initial Content of Time Tag Map Keys Registry Table 4: Initial Content of Time Tag Map Keys Registry
8. Security Considerations 8. Security Considerations
The security considerations of [RFC8949] apply; the tags introduced The security considerations of [RFC8949] apply; the tags introduced
here are not expected to raise security considerations beyond those. here are not expected to raise security considerations beyond those.
Time, of course, has significant security considerations; these Time, of course, has significant security considerations; these
include the exploitation of ambiguities where time is security include the exploitation of ambiguities where time is security
relevant (e.g., for freshness or in a validity span) or the relevant (e.g., for freshness or in a validity span) or the
disclosure of characteristics of the emitting system (e.g., time disclosure of characteristics of the emitting system (e.g., time zone
zone, or clock resolution and wall clock offset). or clock resolution and wall clock offset).
A more detailed discussion of security considerations emanating from A more detailed discussion of security considerations emanating from
using a representation of time that allows the inclusion of complex, using a representation of time that allows the inclusion of complex
possibly inconsistent information is available in Section 7 (Security and possibly inconsistent information is available in "Security
Considerations) of [IXDTF]. Considerations" (Section 7 of [RFC9557]).
9. References 9. References
9.1. Normative References 9.1. Normative References
[BCP26] Cotton, M., Leiba, B., and T. Narten, "Guidelines for [BCP26] Best Current Practice 26,
<https://www.rfc-editor.org/info/bcp26>.
At the time of writing, this BCP comprises the following:
Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/rfc/rfc8126>. <https://www.rfc-editor.org/info/rfc8126>.
[GUM] Joint Committee for Guides in Metrology, "Evaluation of [GUM] Joint Committee for Guides in Metrology, "Evaluation of
measurement data — Guide to the expression of uncertainty measurement data -- Guide to the expression of uncertainty
in measurement", JCGM 100:2008, September 2008, in measurement", JCGM 100:2008, September 2008,
<https://www.bipm.org/en/publications/guides/gum.html>. <https://www.bipm.org/en/publications/guides/gum.html>.
[IANA.cbor-tags] [IANA.cbor-tags]
IANA, "Concise Binary Object Representation (CBOR) Tags", IANA, "Concise Binary Object Representation (CBOR) Tags",
<https://www.iana.org/assignments/cbor-tags>. <https://www.iana.org/assignments/cbor-tags>.
[IEEE1588-2008] [IEEE1588-2008]
IEEE, "IEEE Standard for a Precision Clock Synchronization IEEE, "IEEE Standard for a Precision Clock Synchronization
Protocol for Networked Measurement and Control Systems", Protocol for Networked Measurement and Control Systems",
skipping to change at page 19, line 14 skipping to change at line 805
[IEEE1588-2019] [IEEE1588-2019]
IEEE, "IEEE Standard for a Precision Clock Synchronization IEEE, "IEEE Standard for a Precision Clock Synchronization
Protocol for Networked Measurement and Control Systems", Protocol for Networked Measurement and Control Systems",
IEEE 1588-2019, June 2020, IEEE 1588-2019, June 2020,
<https://standards.ieee.org/ieee/1588/6825/>. Often <https://standards.ieee.org/ieee/1588/6825/>. Often
called PTP v2.1, as it has been designed so it can be used called PTP v2.1, as it has been designed so it can be used
in a way that is fully backwards compatible to in a way that is fully backwards compatible to
IEEE1588-2008. IEEE1588-2008.
[IXDTF] Sharma, U. and C. Bormann, "Date and Time on the Internet:
Timestamps with additional information", Work in Progress,
Internet-Draft, draft-ietf-sedate-datetime-extended-11, 23
October 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-sedate-datetime-extended-11>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8575] Jiang, Y., Ed., Liu, X., Xu, J., and R. Cummings, Ed., [RFC8575] Jiang, Y., Ed., Liu, X., Xu, J., and R. Cummings, Ed.,
"YANG Data Model for the Precision Time Protocol (PTP)", "YANG Data Model for the Precision Time Protocol (PTP)",
RFC 8575, DOI 10.17487/RFC8575, May 2019, RFC 8575, DOI 10.17487/RFC8575, May 2019,
<https://www.rfc-editor.org/rfc/rfc8575>. <https://www.rfc-editor.org/info/rfc8575>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data [RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610, JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/rfc/rfc8610>. June 2019, <https://www.rfc-editor.org/info/rfc8610>.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object [RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949, Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020, DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/rfc/rfc8949>. <https://www.rfc-editor.org/info/rfc8949>.
[RFC9557] Sharma, U. and C. Bormann, "Date and Time on the Internet:
Timestamps with Additional Information", RFC 9557,
DOI 10.17487/RFC9557, April 2024,
<https://www.rfc-editor.org/info/rfc9557>.
[SI-SECOND] [SI-SECOND]
International Organization for Standardization (ISO), ISO, "Quantities and units -- Part 3: Space and time",
"Quantities and units — Part 3: Space and time", ISO 80000-3:2006, March 2006.
ISO 80000-3, 1 March 2006.
[TIME_T] The Open Group Base Specifications, "Vol. 1: Base [TIME_T] IEEE, "The Open Group Base Specifications Issue 7",
Definitions, Issue 7", Section 4.16 'Seconds Since the Section 4.16 Seconds Since the Epoch, IEEE
Epoch', IEEE Std 1003.1-2017, 2018 Edition, 2018, Std 1003.1-2017, 2018,
<http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/ <http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/
V1_chap04.html#tag_04_16>. V1_chap04.html#tag_04_16>.
9.2. Informative References 9.2. Informative References
[C] International Organization for Standardization, [C] ISO, "Information technology -- Programming languages --
"Information technology — Programming languages — C", C", Fourth Edition, ISO/IEC 9899:2018, June 2018,
Fourth Edition, ISO/IEC 9899:2018, June 2018,
<https://www.iso.org/standard/74528.html>. Contents <https://www.iso.org/standard/74528.html>. Contents
available via <https://www.open- available via <https://www.open-
std.org/jtc1/sc22/wg14/www/docs/n2310.pdf std.org/jtc1/sc22/wg14/www/docs/n2310.pdf>
(https://www.open-std.org/jtc1/sc22/wg14/www/docs/
n2310.pdf)>
[ISO8601-1:2019] [ISO8601-1:2019]
ISO, "Date and time — Representations for information ISO, "Date and time -- Representations for information
interchange — Part 1: Basic rules", ISO 8601-1:2019, interchange -- Part 1: Basic rules", ISO 8601-1:2019,
February 2019, <https://www.iso.org/standard/70907.html>. February 2019, <https://www.iso.org/standard/70907.html>.
[ISO8601:1988] [ISO8601:1988]
ISO, "Data elements and interchange formats — Information ISO, "Data elements and interchange formats -- Information
interchange — Representation of dates and times", interchange -- Representation of dates and times",
ISO 8601:1988, June 1988, ISO 8601:1988, June 1988,
<https://www.iso.org/standard/15903.html>. Also available <https://www.iso.org/standard/15903.html>. Also available
from <https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/ from <https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/
fipspub4-1-1991.pdf fipspub4-1-1991.pdf
(https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/ (https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/
fipspub4-1-1991.pdf)>. fipspub4-1-1991.pdf)>.
[RFC3161] Adams, C., Cain, P., Pinkas, D., and R. Zuccherato, [RFC3161] Adams, C., Cain, P., Pinkas, D., and R. Zuccherato,
"Internet X.509 Public Key Infrastructure Time-Stamp "Internet X.509 Public Key Infrastructure Time-Stamp
Protocol (TSP)", RFC 3161, DOI 10.17487/RFC3161, August Protocol (TSP)", RFC 3161, DOI 10.17487/RFC3161, August
2001, <https://www.rfc-editor.org/rfc/rfc3161>. 2001, <https://www.rfc-editor.org/info/rfc3161>.
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
<https://www.rfc-editor.org/rfc/rfc3339>. <https://www.rfc-editor.org/info/rfc3339>.
[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, [RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
"Network Time Protocol Version 4: Protocol and Algorithms "Network Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
<https://www.rfc-editor.org/rfc/rfc5905>. <https://www.rfc-editor.org/info/rfc5905>.
Appendix A. Collected CDDL Appendix A. Collected CDDL
This appendix collects the CDDL rules spread over the document into This appendix collects the CDDL rules spread over the document into
one convenient place. one convenient place.
Etime = #6.1001(etime-detailed) Etime = #6.1001(etime-detailed)
etime-framework = { etime-framework = {
uint => any ; at least one base time uint => any ; at least one base time
skipping to change at page 22, line 25 skipping to change at line 946
time-minute = 2DIGIT ; 00-59 time-minute = 2DIGIT ; 00-59
time-numoffset = ("+" / "-") time-hour ":" time-minute time-numoffset = ("+" / "-") time-hour ":" time-minute
time-zone-initial = ALPHA / "." / "_" time-zone-initial = ALPHA / "." / "_"
time-zone-char = time-zone-initial / DIGIT / "-" / "+" time-zone-char = time-zone-initial / DIGIT / "-" / "+"
time-zone-part = time-zone-initial *13(time-zone-char) time-zone-part = time-zone-initial *13(time-zone-char)
; but not "." or ".." ; but not "." or ".."
time-zone-name = time-zone-part *("/" time-zone-part) time-zone-name = time-zone-part *("/" time-zone-part)
ALPHA = %x41-5A / %x61-7A ; A-Z / a-z ALPHA = %x41-5A / %x61-7A ; A-Z / a-z
DIGIT = %x30-39 ; 0-9 DIGIT = %x30-39 ; 0-9
' ; extracted from [IXDTF] and [RFC3339]; update as needed ' ; extracted from [RFC9557] and [RFC3339]; update as needed
$$ETIME-ELECTIVE //= (-11: suffix-info-map) $$ETIME-ELECTIVE //= (-11: suffix-info-map)
$$ETIME-CRITICAL //= (11: suffix-info-map) $$ETIME-CRITICAL //= (11: suffix-info-map)
suffix-info-map = { * suffix-key => suffix-values } suffix-info-map = { * suffix-key => suffix-values }
suffix-key = tstr .abnf ("suffix-key" .det IXDTF) suffix-key = tstr .abnf ("suffix-key" .det IXDTF)
suffix-values = one-or-more<suffix-value> suffix-values = one-or-more<suffix-value>
one-or-more<T> = T / [ 2* T ] one-or-more<T> = T / [ 2* T ]
suffix-value = tstr .abnf ("suffix-value" .det IXDTF) suffix-value = tstr .abnf ("suffix-value" .det IXDTF)
IXDTF = ' IXDTF = '
key-initial = lcalpha / "_" key-initial = lcalpha / "_"
key-char = key-initial / DIGIT / "-" key-char = key-initial / DIGIT / "-"
suffix-key = key-initial *key-char suffix-key = key-initial *key-char
suffix-value = 1*alphanum suffix-value = 1*alphanum
alphanum = ALPHA / DIGIT alphanum = ALPHA / DIGIT
lcalpha = %x61-7A lcalpha = %x61-7A
ALPHA = %x41-5A / %x61-7A ; A-Z / a-z ALPHA = %x41-5A / %x61-7A ; A-Z / a-z
DIGIT = %x30-39 ; 0-9 DIGIT = %x30-39 ; 0-9
' ; extracted from [IXDTF]; update as needed! ' ; extracted from [RFC9557]; update as needed!
Duration = #6.1002(etime-detailed) Duration = #6.1002(etime-detailed)
Period = #6.1003([ Period = #6.1003([
start: ~Etime / null start: ~Etime / null
end: ~Etime / null end: ~Etime / null
? duration: ~Duration / null ? duration: ~Duration / null
]) ])
clumsy-Period = #6.1003([ clumsy-Period = #6.1003([
(start: ~Etime, (start: ~Etime,
skipping to change at page 23, line 27 skipping to change at line 992
duration: ~Duration))) // duration: ~Duration))) //
(start: null, (start: null,
end: ~Etime, end: ~Etime,
duration: ~Duration) duration: ~Duration)
]) ])
etime = #6.1001({* (int/tstr) => any}) etime = #6.1001({* (int/tstr) => any})
duration = #6.1002({* (int/tstr) => any}) duration = #6.1002({* (int/tstr) => any})
period = #6.1003([~etime/null, ~etime/null, ~duration/null]) period = #6.1003([~etime/null, ~etime/null, ~duration/null])
Figure 6: Collected CDDL rules from this specification Figure 6: Collected CDDL Rules from This Specification
Acknowledgements Acknowledgements
The authors would like to acknowledge the many comments from members The authors would like to acknowledge the many comments from members
of the CBOR WG, Francesca Palombini for her AD review, and Thomas of the CBOR WG, Francesca Palombini for her AD review, and Thomas
Fossati and Qin Wu for their directorate reviews. Fossati and Qin Wu for their directorate reviews.
Authors' Addresses Authors' Addresses
Carsten Bormann Carsten Bormann
 End of changes. 93 change blocks. 
268 lines changed or deleted 250 lines changed or added

This html diff was produced by rfcdiff 1.48.