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Re: [art] New Version Notification for draft-touch-time-05.txt

Steve Allen <sla@ucolick.org> Tue, 12 November 2019 07:47 UTC

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Date: Mon, 11 Nov 2019 23:47:16 -0800
From: Steve Allen <sla@ucolick.org>
To: Joe Touch <touch@strayalpha.com>
Cc: "art@ietf.org" <art@ietf.org>
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Subject: Re: [art] New Version Notification for draft-touch-time-05.txt
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On Mon 2019-11-11T18:57:53-0800 Joe Touch hath writ:
> A little more about PTP, found here:
> https://www.iol.unh.edu/sites/default/files/knowledgebase/1588/ptp_overview.pdf

> The source above claims PTP tries to coordinate the local clock to TAI.
>
> That doc confirms it isn’t a time scale, as I originally indicated.

In many cases it does not really matter whether a particular instance
of PTP is trying to match TAI or any other atomic time scale.

The issues of Bulletin Horaire show that the value of TAI is based on
re-setting all atomic time scales so that they all had
UT2(BIH) - A3 = -1.4123 s
at the epoch 1961-01-01T20:00:00 UT2.
https://www.ucolick.org/~sla/leapsecs/taiepoch.html

The offsets of GPS and other satellite systems are also arbitrary, so
the value of any atomic time scale is unrelated to any observable
phenomenon.

What matters is that the time scale used by a PTP implementation is
uniform within the scope of its systems.

--
Steve Allen                    <sla@ucolick.org>              WGS-84 (GPS)
UCO/Lick Observatory--ISB 260  Natural Sciences II, Room 165  Lat  +36.99855
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