[ntp:questions] Will ntpd tell me if it encounters problems?

David Woolley david at djwhome.demon.co.uk
Thu Apr 12 06:47:39 UTC 2007


In article <461D66AA.6010409 at comcast.net>,
Richard B. gilbert <rgilbert88 at comcast.net> wrote:

> I may be wrong but I believe that "synchronization distance" is the 
> criteria for selecting the synchronization source from the selection 
> set.  Since synchronization distance is one half the round trip delay 

It's the criterion for selecting the source that is reported in an
rv command and from which the reference ID is derived.  However all the
sources with a plus or star are included in the calculation of the time.
They are weighted by a combination of synchronisation distance and stratum.

A large distance also doesn't prevent the server helping to vote out a
rogue server with a low distance.

Very large distances (e.g. those resulting from using W32Time with a local
clock as source) will cause the server to be completely rejected.

> It's generally possible to find servers with delays less than twenty 
> milliseconds.  It should almost always be possible to find servers with 
> delays less than 50 milliseconds.

This assumes that you are not using a low latency connection.  The minimum
delay for a 33k modem is well over 100ms, and I get about 27ms for an ISP
server on interleaved ADSL (50 is OK in that case, but someone suggested
20 before).




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