[Interest] Packet arrival-time resolution? QUdpSocket

Shawn Rutledge Shawn.Rutledge at qt.io
Mon Nov 27 17:33:09 CET 2017


On 27 Nov 2017, at 16:45, Konrad Rosenbaum <konrad at silmor.de> wrote:
> 
> Yes, the NTP people have done this. Extensively over several decades.
> Please defer to their expertise and use NTP for time sync. ;-)
> 
> Using TCP for this purpose is really a bad idea too - because of the built
> in delays and repeat intervals.
> 
> As for estimates of accuracy:
> 
> If you are not a real-time process you can rely on 100ms accuracy 99% of
> the time if the system load is low; anything below 10ms is simply noise.

NTP works fine for most purposes.  But you can get the clocks synced to a higher accuracy with PTP: https://en.wikipedia.org/wiki/Precision_Time_Protocol  It can be worthwhile for a sensor network with multiple controller CPUs, where you want to make sure all the sensor readings have really accurate timestamps, so that they mesh together into a single timeline.  In such a case you might want to use PTP to sync them all to an accurate master clock (such as from a GPS receiver).




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