[ntp:questions] Re: offset values from ntpq and ntptrace

Danny Mayer mayer at ntp.isc.org
Sun Apr 2 04:08:35 UTC 2006

Tanguy.ropitault at gmail.com wrote:
> I know that sometimes, it's boring to anwser to simple questions but
> one more time, you don't answer to my question... juste make a sentence
> please for explaining. Estimated error is the estimated error compared
> to the server time, or compared to the reference clock? For me, it's
> compared to the server time but I'm not sure. And also, the estimated
> error is the estimated of the offset measured or estimated error is the
> difference estimated between client clock and server clock??? For me
> it's the estimated error between client clock and server clock because
> estimated error is higher than offset...

Whatever else is the answer to your questions, the estimated value of
the offset has absolutely nothing to do with the estimated error. The
offset is an estimate of the difference between the time of the server
source and the client. The error is due to the vagaries of the packet
getting from the server to the client, which is due to a large number of
factors, including routers, switches, bridges, network traffic and
congestion, hardware and software, and the list goes on. You can't even
be sure that the return packet went via the same route as the sent
packet and it is usually true that the outbound trip time is not the
same as the return trip time.


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