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Re: [Ntp] comments on draft‑mlichvar‑ntp‑ntpv5‑03

Dan Drown <dan-ntp@drown.org> Fri, 26 November 2021 02:43 UTC

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Date: Thu, 25 Nov 2021 20:43:00 -0600
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From: Dan Drown <dan-ntp@drown.org>
To: Steven Sommars <stevesommarsntp@gmail.com>
Cc: NTP WG <ntp@ietf.org>
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Subject: Re: [Ntp] comments on draft‑mlichvar‑ntp‑ntpv5‑03
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Quoting Steven Sommars <stevesommarsntp@gmail.com>:
> Root dispersion should have the same resolution as the time stamp.
> With today's 16-bit field the smallest root dispersions are 0,   15.3,
> 30.5 ... microseconds.
> What should an NTP server having 1 microsecond uncertainty return?

I agree that NTPv4 root dispersion does not have enough resolution.

With this NTPv5 spec, root dispersion is 32 bits with 28 bits assigned  
to the subsection fraction. This gives 1/(2^28) or 3.7 nanosecond  
resolution. I don't see the point in taking root dispersion from 32  
bits to 64 bits for a smaller resolution than that.

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