[ntp:questions] Re: Synchronization with mobile devices and different time zones

Brad Knowles brad at stop.mail-abuse.org
Mon Oct 25 10:17:29 UTC 2004

At 2:50 AM -0700 2004-10-25, Sergio wrote:

>  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?

	NTP is designed to be used in environments were you occasionally 
lose connectivity, packets are dropped, etc....  If it doesn't get a 
response this time, then it will try again in the future.  This 
doesn't normally pose a serious problem unless you lose a lot of 
packets over a long period of time.

	NTP works pretty hard to always speed up or slow down the clock 
and tries to avoid stepping the clock one way or the other.  So, if 
you've been in operation with good connectivity for a while, then 
being disconnected for a time shouldn't hurt too much -- your clock 
may drift a bit more than usual, but that should be about as far as 
it goes.

	Things get more difficult if your IP address changes, as is more 
common for laptops.  In that case, you need to either quit and 
restart the NTP daemon (perhaps with a configuration file that is 
more suitable for your new location), or at least drop all your 
current associations and set up new ones (or re-set up the same old 
ones, but making the daemon aware of your new IP address).

Brad Knowles, <brad at stop.mail-abuse.org>

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."

     -- Benjamin Franklin (1706-1790), reply of the Pennsylvania
     Assembly to the Governor, November 11, 1755

   SAGE member since 1995.  See <http://www.sage.org/> for more info.

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