[ntp:questions] Re: Strange scattergram

Brian Utterback brian.utterback at sun.removeme.com
Wed May 17 16:15:30 UTC 2006

Karel Sandler wrote:
> Hello,
> to better know the network quality between my S2 and its peers, the wedge 
> scattergrams were used. That strange one has the upper limb prolonged down 
> to the left side of the head. Only few samples (status 9314) are located 
> there but their existence is beyond all my understanding.
> Hope my S2 works well, only one plot (one peer from seven) shows up that 
> feature - lx.ujf.cas.cz/ntp-lx/antitail.png .
> --
> K. Sandler 

I wouldn't worry too much about the continuation of the line down and
towards the left. That is probably due to the fact that the systems
clock is in the process of slewing and is in the "overshoot" part of
the phase locked loop. Of much greater concern is the complete asymmetry
of the wedge plot. The typical cause for having the wedge plot bunched
up towards one limb or the other is an asymmetric network path between
the client and the server. However, looking at the offset plots
at http://lx.ujf.cas.cz/ntp-lx it looks to me like your ntpd is not
disciplining the frequency at all. Your system clock runs fast and
ntpd adjusts it back in what look to me to be about a two hour cycle.
I think that is why all of the offsets are positive in the wedge plot,
because your clock runs fast.


Rose are #FF0000, Violets are #0000FF. All my base are belong to you.
Brian Utterback - OP/N1 RPE, Sun Microsystems, Inc.
Ph:877-259-7345, Em:brian.utterback-at-ess-you-enn-dot-kom

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