rfc9581v4.txt		rfc9581.txt
	skipping to change at line 314 ¶		skipping to change at line 314 ¶
	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. For example,		platform, care has to be taken to meet its invariants. For example,
	for C timespec, the fractional part tv_nsec needs to be between 0		for C timespec, the fractional part tv_nsec needs to be between 0
	inclusive and 10^9 exclusive, which can be achieved by also adjusting		inclusive and 10^9 exclusive, which can be achieved by also adjusting
	the base time appropriately.		the base time appropriately.
	3.4. Keys -1, -13, and 13: Timescale		3.4. Keys -1, -13, and 13: Timescale
	Keys -1, -13, and 13 are used to indicate a timescale, where key 13		Keys -1, -13, and 13 are used to indicate a timescale, where key 13
	is critical. Keys -1 and -13 have identical semantics (they are both		is critical. Keys -1 and -13 have identical semantics (they are both
	assigned as key -1 was chosen first and then, when key 13 was added,		assigned because key -1 was chosen first and then, when key 13 was
	it appeared desirable to have a negative equivalent). Each extended		added, it appeared desirable to have a negative equivalent). Each
	time data item MUST NOT contain more than one of these keys. The		extended time data item MUST NOT contain more than one of these keys.
	value 0 indicates UTC, with the POSIX epoch [TIME_T]; the value 1
			The value 0 indicates UTC, with the POSIX epoch [TIME_T]; the value 1
	indicates TAI, with the Precision Time Protocol (PTP) epoch (1		indicates TAI, with the Precision Time Protocol (PTP) epoch (1
	January 1970 00:00:00 TAI, see [IEEE1588-2019] or [IEEE1588-2008]).		January 1970 00:00:00 TAI, see [IEEE1588-2019] or [IEEE1588-2008]).
	$$ETIME-ELECTIVE //= (-1 => $ETIME-TIMESCALE)		$$ETIME-ELECTIVE //= (-1 => $ETIME-TIMESCALE)
	$$ETIME-ELECTIVE //= (-13 => $ETIME-TIMESCALE)		$$ETIME-ELECTIVE //= (-13 => $ETIME-TIMESCALE)
	$$ETIME-CRITICAL //= (13 => $ETIME-TIMESCALE)		$$ETIME-CRITICAL //= (13 => $ETIME-TIMESCALE)
	$ETIME-TIMESCALE /= &(etime-utc: 0)		$ETIME-TIMESCALE /= &(etime-utc: 0)
	$ETIME-TIMESCALE /= &(etime-tai: 1)		$ETIME-TIMESCALE /= &(etime-tai: 1)
	skipping to change at line 354 ¶		skipping to change at line 355 ¶
	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 timescales (such		| possibly for specific realizations of abstract timescales (such
	| as TAI(USNO), the specific realization obtained at the United		| as TAI(USNO), the specific realization obtained at the United
	| States Naval Observatory), which is more accurate as a constant		| States Naval Observatory, which is more accurate as a constant
	| offset basis for GPS times). While the registration process		| offset basis for GPS times). While the registration process
	| itself is trivial, these registrations need to be made based on		| itself is trivial, these registrations need to be made based on
	| a solid specification of their actual definition.		| 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],
	skipping to change at line 413 ¶		skipping to change at line 414 ¶
	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 of		Key -7 (Uncertainty) can be used to represent a known uncertainty of
	uncertainty for the clock as a numeric value in seconds or as a		measurement 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
	skipping to change at line 633 ¶		skipping to change at line 634 ¶
	duration: ~Duration)		duration: ~Duration)
	])		])
	6. CDDL Type Names		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])
	Figure 5: Recommended Type Names for CDDL		Figure 5: Recommended Type Names for CDDL
	7. IANA Considerations		7. IANA Considerations
	7.1. CBOR Tags		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.		tags in Table 2.
	skipping to change at line 663 ¶		skipping to change at line 664 ¶
	Table 2: Values for Tags		Table 2: Values for Tags
	IANA has updated the "Data Item" column for tag 1003 from "map" to		IANA has updated the "Data Item" column for tag 1003 from "map" to
	"array".		"array".
	7.2. Timescales Registry		7.2. Timescales Registry
	Per this specification, IANA has created a new "Timescales" registry		Per this specification, IANA has created a new "Timescales" registry
	within the "Concise Binary Object Representation (CBOR) Tags"		within the "Concise Binary Object Representation (CBOR) Tags"
	registry group [IANA.cbor-tags]. The registration procedure is both		registry group [IANA.cbor-tags]. The registration procedure requires
	"Expert Review" and "RFC Required" (Sections 4.5 and 4.7 of RFC 8126		both "Expert Review" and "RFC Required" (Sections 4.5 and 4.7 of RFC
	[BCP26], respectively).		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 |
	skipping to change at line 994 ¶		skipping to change at line 995 ¶
	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 [RFC9557]		' ; extracted from [RFC9557]
	Duration = #6.1002(etime-detailed)		Duration = #6.1002(etime-detailed)
	Period = #6.1003([		simple-Period = #6.1003([
	start: ~Etime / null		start: ~Etime / null
	end: ~Etime / null		end: ~Etime / null
	? duration: ~Duration / null		? duration: ~Duration
	])		])
	clumsy-Period = #6.1003([		Period = #6.1003([
	(start: ~Etime,		(start: ~Etime,
	((end: ~Etime,		((end: ~Etime) //
	? duration: null) //
	(end: null,		(end: null,
	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])
	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, Thomas Fossati
	Fossati and Qin Wu for their directorate reviews.		and Qin Wu for their directorate reviews, and Rohan Mahy for one more
			review late in the process.
	Authors' Addresses		Authors' Addresses
	Carsten Bormann		Carsten Bormann
	Universität Bremen TZI		Universität Bremen TZI
	Postfach 330440		Postfach 330440
	D-28359 Bremen		D-28359 Bremen
	Germany		Germany
	Phone: +49-421-218-63921		Phone: +49-421-218-63921
	Email: cabo@tzi.org		Email: cabo@tzi.org
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