[ntp:questions] Re: ntpd Not Converging

David T. Ashley dta at e3ft.com
Fri Nov 4 14:31:53 UTC 2005


Thanks to everyone who responded.  I do appreciate all of the good advice 
about not using Stratum 1 servers during development, etc.

But the replies did not zero in on the key question.  It is a control law 
question.  When ntpd starts and the server time is off of the true time by 
an offset (say, 2 seconds), what "control law" does it apply to reconverge 
the server's time and the true time?

Again, when I start ntpd with /var/lib/ntp/drift not present, it always 
works.  I've noticed that ntpd waits about an hour and 15 minutes to use the 
time difference to adjust the "frequency" of the kernel timing parameters to 
go towards convergence.  It is only when the drift file exists that it 
doesn't seem to try to converge the server's time and the true time.

I've adjusted my startup to always delete /var/lib/ntp/drift, and this works 
fine.  But I'd like to understand the control law involved.

By "control law" I mean the discrete time transfer function that influences 
the stability and long-term convergence characteristics of the system.

I appreciate all of the replies.  But none of them seem centered on the core 
issue, which is the control law.

Thanks, Dave. 






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