[ntp:questions] different request pattern

David Woolley david at ex.djwhome.demon.co.uk.invalid
Tue Jul 1 07:10:19 UTC 2008


arne_woerner at yahoo.com wrote:

> 2. "offset per second" describes the estimated offset-difference after
> a second...
> i compute it like this (dont laugh :-) ):
> (adjtime_offsets + estimated_offset_to_server_X)/T
> let T be the time when the offset to server X was 0
> let adjtime_offsets be the sum of the adjtime() offsets in the last T
> seconds...

That seems to me to be an estimate of the local machine's clock 
frequency, evaluated over an excessively short period in relation to 
network timing jitter.  10ms/s would be 10,000 parts per million, which 
is much much higher than you would get even from a real false ticker, 
and could only really represent the result of jitter.  On a heavily 
loaded connection, traffic variations can results in offsets varying by 
hundreds of milliseconds (relative to true time).




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