[ntp:questions] What is the NTP recovery time from 16s step in GPS server?

David Woolley david at ex.djwhome.demon.invalid
Tue Oct 30 17:57:57 UTC 2012

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.

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