[time-nuts] sync computer clock ticks
hmurray at megapathdsl.net
Sat Jan 5 17:33:37 EST 2008
> The company i work for makes high performance interconnect solutions
> for super computers. i'm working on a demo where we're sending data
> around a ring and i wanted to timestamp all the packets as it hits
> each node of the ring. the servers could be under some stress when
> this is running.
A microsecond is pretty tight.
There is a chicken/egg tangle here. If you know the network is good then
you can use that to calibrate your clocks. If you know the clocks are good
then you can use that to calculate network delays.
What's the round trip time when the network is idle?
Would something like the following work?
run a calibration step on an idle system
run your tests
run another calibration step
post process the data
If the two calibration steps agree, then you can just fixup the offsets.
If they differ, you may have to try linear interpolation.
These are my opinions, not necessarily my employer's. I hate spam.
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