[time-nuts] NIST UT1 NTP server results
Mike Cook
michael.cook at sfr.fr
Fri Jul 22 23:21:34 UTC 2016
> Le 23 juil. 2016 à 00:23, John Hawkinson <jhawk at mit.edu> a écrit :
>
> I have to wonder if it's really such a great idea to have this
> as an open NTP server without huge red flags that it is not UTC.
> One could imagine it leading to big problems if some people started
> syncing to it without undersatnding that it was.
I think that it would get rejected as a falseticker in most circumstances.
Worth looking at.
I have just started an NTP client with just that server as a source.. The GPS based source is configured noselect.
Sat Jul 23 01:00:27 CEST 2016
remote refid st t when poll reach delay offset jitter
==============================================================================
192.168.1.23 .GPS. 1 u 15 16 377 0.837 70.330 39.176
128.138.140.50 .NIST. 1 u 12 16 377 130.662 -153.05 35.809
Sat Jul 23 01:01:31 CEST 2016
remote refid st t when poll reach delay offset jitter
==============================================================================
192.168.1.23 .GPS. 1 u 7 16 377 0.825 106.345 40.264
128.138.140.50 .NIST. 1 u 12 16 377 130.652 -121.03 35.812
The system clock offset is slowly converging on the UT1 server.
more later.
>
> Has there been thought to at least setting the reference ID to 'UT1'
> instead of 'NIST' (or maybe 'NUT1' since 'NIST-UT1' is too long?).
>
I would prefer UT1
>
> With respect to interpolation and soforth, it seems like a lot of NTP
> cares more about frequency than offset, and all this stepping presumably
> wreaks havoc with the frequency? Maybe I'm wrong though...
>
> --jhawk at mit.edu
> John Hawkinson
>
> Tom Van Baak <tvb at LeapSecond.com> wrote on Fri, 22 Jul 2016
> at 15:14:26 -0700 in <60BA6696E49A4C4FA9F6B5792176F81A at pc52>:
>
>
>>> The current algorithm on the server uses the UT1 offset from
>>> Circular A with no interpolation. The value changes at 0 UTC every day.
>>> I did not use any interpolation because the difference in the dUT1
>>> value from one day to the next is on the order of 1-2 ms, and I
>>> considered that it was likely that the jitter and asymmetry of the
>>> network connection to a typical user would limit the accuracy to a
>>> larger value anyway so that interpolation would not actually improve
>>> anything. However, I will certainly consider changing this. It would not
>>> be a big deal to add interpolation if there were some good reason for
>>> doing so.
>>>
>>> Best wishes,
>>>
>>> Judah Levine
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