[ntp:questions] Re: Synchronization with mobile devices and different time zones
David J Taylor
david-taylor at blueyonder.co.not-this-bit.nor-this-part.uk
Mon Oct 25 10:18:52 UTC 2004
> I see. Thanks a lot for the clarification, I certainly was confused
> about the time zones issue.
> Well, then it's possible. But I assume there is a certain overload
> involved. If a communication takes place once every seventeen minutes
> and that communication is lost (e.g., no network connection
> available), either the clock will not be synchronized until the next
> synchronization point (17 minutes later) or the communication will be
> retried until it is successful, right?
You would normally configure NTP to talk to at least four servers, so the
communication would be with each server every 1024 seconds (once things
had settled down - during startup the communication is more frequent).
Yes, if communication is lost, the clock free runs, but understand that
NTP alters the clock rate as well as it's offset, so once the clock is
synchronised (to use your term), the drift rate of the clock will be
adjusted so that sync is maintained. Hence, if contact with the set of
servers is lost, the clock will continue to run near to the correct time,
with a small but increasing error as time goes by. NTP does /not/ step
the clock at every adjustment, but tries to eliminate the clock drift by
altering its frequency. At startup, the drift from the previous NTP run
is used as the starting point for drift estimation.
I've simplified this down to my level of knowledge in the hope that it
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