[ntp:questions] Extracting ntpq like information programmatically

David Woolley david at ex.djwhome.demon.invalid
Tue Apr 2 07:49:00 UTC 2013


unruh wrote:

> needs to remember only the last couple of measurements. It is a Markovian
> process. 
> 

Which is s statistics term.  The biggest difference between chrony and 
ntpd, is that chrony seems to have been designed using statistics 
algorithms (linear filters), and ntpd using engineering ones (digital 
filters and PI controllers).  There is a culture clash at work here.

ntpd is definitely an infinite impulse response system.  I think chrony 
is a finite impulse response one. FIR ones will fully accommodate a real 
change in a finite time, but will also do so for a persistent error.



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