Re: [Ntp] NTS4UPTP Rev 03 - Formal request for WG adoption

Miroslav Lichvar <mlichvar@redhat.com> Mon, 07 June 2021 09:05 UTC

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Date: Mon, 7 Jun 2021 11:05:19 +0200
From: Miroslav Lichvar <mlichvar@redhat.com>
To: Danny Mayer <mayer@pdmconsulting.net>
Cc: Heiko Gerstung <heiko.gerstung=40meinberg.de@dmarc.ietf.org>, NTP WG <ntp@ietf.org>, Daniel Franke <dfoxfranke@gmail.com>
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Subject: Re: [Ntp] NTS4UPTP Rev 03 - Formal request for WG adoption
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On Wed, Jun 02, 2021 at 09:38:41AM +0200, Miroslav Lichvar wrote:
> With a 1000x smaller jitter you need a 1000x shorter
> polling interval to fully take advantage of it, assuming everything
> else is the same.

I'm sorry for posting nonsense like this. People who remember how a
typical ADEV plot looks like (with the -1 and +1/2 slopes) probably
knew this was wrong. It should be only 100x shorter polling interval
for 1000x smaller jitter (a slope of 2/3).

I think PTP using 128 sync messages per second is more about filtering
measurements (effectively decreasing the jitter), rather than
the instability of the clock.

-- 
Miroslav Lichvar