[ntp:questions] Ignore one server except in extreme conditions?

Miguel Gonçalves mail at miguelgoncalves.com
Wed Nov 16 16:23:16 UTC 2011


Hi!

On 16 November 2011 16:11, A C <agcarver+ntp at acarver.net> wrote:

> On 11/16/2011 00:15, Harlan Stenn wrote:
>
>> What sort of offset/jitter are you seeing on the NMEA signal?  By
>> default we expect it to be correct to about 2ms.
>>
>
> I posted more data in another reply but the NMEA tends to have offsets of
> +/- 50 ms and jitters of +/- 10 ms while the PPS and Internet servers are
> all much more stable.  PPS has a jitter of only 0.061 ms reported by ntpd
> (but probably better than that, the jitter value never drops below 0.061
> for any server, in fact it's present in the entire billboard jitter column
> when ntpd first starts up so it must be a floating point
> calculation/rounding issue).  A couple of the Internet servers can wander
> off if the network is bad but most of them stay within +/- 5 ms of offset
> and +/- 1 ms of jitter.
>

In one of my servers I have

tos mindist 0.250

This enables PPS and NMEA to differ 250 ms. I hope I am not saying anything
wrong but you can check the NTP documentation regarding this keyword.

Cheers,
Miguel


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