[ntp:questions] What is the "best" synchronization possible over the network?
unruh-spam at physics.ubc.ca
Wed Feb 11 23:45:51 UTC 2009
ntp at tla.org (John Ioannidis) writes:
>The problem setup: two locations, both within the United States, neither
>has roof access so no GPS reception is possible. How do you synchronize
What about window access? And since you have money, I am sure that your
building does have a roof. Stick a cheap computer near the roof and run a
GPS18 onto the roof and a cable down to that computer. (Nota that you can
extend the line beyond the 5M that the GPS18 comes with -- to get really
best results with an amplifier and matched lines, and run the wires down to
Ie, set up fast amps connected with cat 5 cable and 100ohm termnation on
>them with better than 50-microsecond accuracy? Straight NTP over the
>Internet doesn't do the trick. They don't need to actually be
Sure it does. have one of them as a client of the other and on a local
ethernet you should be able to get 50usec agreement.
>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).
Is running a single Cat5 to the roof 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
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