Re: [Ntp] Timescales, leapseconds and smearing

[Steve Allen <[e-mail]>]

On Tue 2020-12-08T10:31:04+0100 Miroslav Lichvar hath writ:
> On Mon, Dec 07, 2020 at 11:27:35PM +0100, Kurt Roeckx wrote:
> > The proposed draft has support for the first 4, and offsets
> > between some of them. Note that it calls the NTP timescale
> > UTC, which it's not.
>
> How do you suggest it should be called?

More generally, I think that names of the time scales in the document
all need an introductory explanation of what they mean.

Look at monthly issues of BIPM Circular T and it becomes evident that
there is no "UTC" which is available in real time.  Sources of time
which can be used by an NTP server there are only
UTC(pick a laboratory)

Note in the issues of Circular T that the Bulgarian Institute of
Metrology (BIM) has had UTC-UTC(BIM) values around 12 microseconds
during the entire year 2020.  Nevertheless, UTC(BIM) is the legal
time in Bulgaria, and devices in Bulgaria might be constrained by
regulations that require they use UTC(BIM) rather than another
UTC which is in better agreement with the rest of the world.

The draft does not mention the source or authority for the values of
UTC, UT1, TAI which are provided by NTP.  The draft almost certainly
cannot specify particular sources of time values, and in the case of
TAI there can be no source because TAI is not defined until next
month when Circular T is published for this month.

The draft should include definitions for UTC, TAI, UT1 as used by NTP.
At least for the case of TAI (but maybe for the other time scales
also) the draft should include explicit text indicating that in the
context of NTP those terms are used in a generic sense that does not
specify how the values of time from NTP are related to the actual
authoritative sources of those time scales.

--
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