[ntp:questions] time delta between clients

Tom Smith smith at cag.zko.hp.com
Sun Dec 23 13:52:36 UTC 2007


Per Hedeland wrote:
> Well, I guess I'm also still wondering whether the
> latter is actually saying that it won't be possible to get the skew
> below 20 ms with Unix hosts with 100Hz clocks, but it's not really
> important - the important thing is that such a statement (if made) is
> not correct.
> 

Well, first I missed it if Rick said he was exclusively concerned about
UNIX hosts. Second, if you check, my comment was also not exclusively about
UNIX hosts, nor about the nominal clock frequency, but about the clock
resolution, or minimum increment from, for example, gettimeofday(). With
those thoughts in mind, yes, the comment stands that the skew that can be
held between any 2 hosts depends on the clock resolutions of the 2 hosts
and this ranges up to 15-16 milliseconds for some and up to 1 millisecond
even for some UNIX systems. Since Rick is concerned about differentiating
delays in the 10s of microseconds over a relatively short test time, this
might be of some importance to him.

-Tom




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