[time-nuts] NIST UT1 NTP server results

Mike Cook michael.cook at sfr.fr
Fri Jul 22 19:21:34 EDT 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
==============================================================================    .GPS.            1 u   15   16  377    0.837   70.330  39.176  .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
==============================================================================    .GPS.            1 u    7   16  377    0.825  106.345  40.264  .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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