[ntp:questions] frequency adjusting only

David Woolley david at ex.djwhome.demon.co.uk.invalid
Tue Apr 22 21:17:07 UTC 2008


maxime louvel wrote:

> My goal is to achieve a synchronisation between the nodes (not with the
> public NTP server) within 50 usec.

I think you can rule out using -x, then.  50 microseconds is pretty 
tight timing and basically requires that you use the kernel time 
discipline, as well as paying careful attention to system and network 
loading and interrupt latencies, both for timing and for the external 
events that you are timing.

On the other hand, if you are tracking to 50 microseconds, you have a 
safety margin of over 200,000% before you risk a step.

I would say forget about slew only mode and worry about fine timing. 
Also use a GPS clock with a PPS output on your primary server.  I don't 
think it will be stable enough to ensure 50 microsecond lock for the 
network, when using an internet server, although using broadcast may 
help, as it may make the clients tend to wander together.




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