Message from discussion What is the NTP recovery time from 16s step in GPS server?
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From: David Taylor <david-tay...@blueyonder.co.uk.invalid>
Subject: Re: What is the NTP recovery time from 16s step in GPS server?
Date: Tue, 30 Oct 2012 19:21:46 +0000
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On 30/10/2012 17:57, David Woolley wrote:
> David Taylor wrote:
>> However, suppose I had /only/ the GPS receiver? NTP has the GPS time
>> and the PPS signal for the exact second, syncs, and then a few minutes
>> in the time suddenly changes by 16 seconds. I would hope that then
>> causes NTP to step the clock onto UTC rather than GPS time. I realise
>> that the time for the GPS receiver to be sending UTC rather than GPS
>> time varies, but how long might it then take NTP to react to the 16
>> second change, and alter the system clock? Both the PPS and the gpsd
>> are being polled at fixed 16 second intervals.
> It's not a specified characteristic, as it is a GIGO case. However, I
> believe it it is the order of 20 minutes, with standard parameters. Most
> of this is for ntpd to convince itself that the local clock time it has
> really is wrong.
Thanks, David. Do you think that it would still be 20 minutes when the
clock in question is being polled every 16 seconds?