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Re: [Ntp] Timescales, leapseconds and smearing

Steve Allen <sla@ucolick.org> Tue, 08 December 2020 20:49 UTC

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Date: Tue, 08 Dec 2020 12:49:40 -0800
From: Steve Allen <sla@ucolick.org>
To: NTP WG <ntp@ietf.org>
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Subject: Re: [Ntp] Timescales, leapseconds and smearing
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On Tue 2020-12-08T21:32:15+0100 Kurt Roeckx hath writ:
> Whatever value is used in NTP, it's never the true value, it's
> always an estimate.

Please explain this in the document.

> The TAI value we would use is an estimate of
> TAI with error bounds. If BIM is off by 12 us, and BIM is used as
> a source for NTP, they can either compensate for that 12 us, or add
> the 12 us in the error calculation.

Rather than TAI I suggest TAI-like, specifically with a parameter N that
allows the time scale to be N seconds different than TAI.
Particular values of N would be

TAI -  0        attempting to match what TAI should be
TAI - 10        the POSIX time_t value used for IANA tz "right" zones
TAI - 19        the source is GPS system time or Galileo system time
TAI - 33        the source is BeiDou system time
TAI - 37        the source is Windows10 system time (after 2017-01-01)
TAI -  N        this futureproofs for the next purely atomic source of time

--
Steve Allen                    <sla@ucolick.org>              WGS-84 (GPS)
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