[ntp:questions] Re: NTP adjustment mechanism

Drk Ryan ryandrk at hotmail.com
Tue Sep 2 18:40:05 UTC 2003

J.B.Swenker at KPN.com (Johan Swenker) wrote in message news:<bj1sku$nfr$1 at hdxl22.telecom.ptt.nl>...
> In article <de98eac0.0308310524.75ee06c2 at posting.google.com>, 
> ryandrk at hotmail.com says...
> >
> >If clock adjustment is limited by tickadj/ticksize eg 4/10000 = +-400
> >ppm , will this essentially mean that for a +100 ppm clock drift, NTP
> >will run at -400 ppm for the first 0.25 of each second making
> >adjustments each tick => accumulate an error (relative to actual
> >clock) of -100 usec and then over that second the actual clock will
> >gain +100 => balance out ..=> this means that worst case scenario NTP
> >error will be at 0.25 sec in each sec interval and will be -100 (due
> >to adj mechanism) +25 (accumulated error at thsi stage due to inherent
> >error) = -75 msec...is this correct?
> No, in your example NTP will adjust the clock for the error of 100 ppm. The 
> limiting means that NTP cannot discipline the clock outside the limits. Within 
> the limits it can do nearly everything.
> Regards, Johan

Hi Johan,
When you say "limits" are you refering to the +/- 400ppm? If yes, then
where is the problem adjusting the clock for the error of 100 ppm
within these limits?


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