[ntp:questions] What is the "best" synchronization possible over the network?

Richard B. Gilbert rgilbert88 at comcast.net
Wed Feb 11 04:30:33 UTC 2009

John Ioannidis wrote:
> The problem setup: two locations, both within the United States, neither 
> has roof access so no GPS reception is possible.  How do you synchronize 
> them with better than 50-microsecond accuracy?  Straight NTP over the 
> Internet doesn't do the trick.  They don't need to actually be 
> synchronized to "real" time, they only need to be synchronized to each 
> other.  Assume reasonably unlimited resources (running a private fiber 
> plant across the continent *is* unreasonable).
> I've looked into slaving something off a voice-carrier time base, but 
> that's not accurate enough.  Maybe something over raw SONET would do the 
> trick?
> Thanks
> /ji

Two Atomic Clocks??  I suspect they would cost far more than you are 
willing/able to spend but they would get the job done!

You could try putting a GPS antenna in a window with a southern 
exposure.  With the proper GPS hardware and software, once you know your 
exact latitude, longitude, and elevation, you only need *one* satellite 
to get the time.

More information about the questions mailing list