Terje, Isn't a good thing that if two clocks disagree they are discarded? It's excellent! The local clock has PPS, therefore chances are that it is accurate (based on historical data). The good frequency stability values, provided by PPS, implies that time accuracy should be maintained even if several samples are discarded.
Assuming that the probability of jitter for different packets is uncorrelated, only packets providing similar error values are used. While large discrepancies are thrown out. Even for two packets, if they agree on the measured error, the probability is that they are correct; if they disagree it is not possible to take a decision and it is better relay on the local clock. Also, in my experience, I never seen samples being discarded... clock hopping is the usual behaviour... But when it comes to NTP, experience is often not enough! Mauro > Mauro Fiacco wrote: > > The only difference is that NTP server #3 employs two servers for > > time synchronisation, while NTP server #4 employs only one server. > > I think the only difference is the working of the clustering algorithm. > > The use of two NTP servers improves stability and accuracy when compared > > to only one servers. > _Never_ use two sources! > You should always use either 1 or at least 4, having just two means that > if those two should ever disagree about the correct time, your client > will disregard both. > Terje -- Mauro Fiacco URL: www.ipaccess.com _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
