[time-nuts] LTE-Lite module

Tom Van Baak tvb at LeapSecond.com
Mon Oct 20 11:30:17 EDT 2014


> http://phk.freebsd.dk/time/20141018.html

PHK,

This is the best news I've heard in a long time; an overhaul of NTP!

One suggestion I'd like to make. You've seen the GPSDO simulator code I started:
http://leapsecond.com/tools/gpsim1.c
And you've seen the growing collection of GPS receiver and OCXO oscillator raw data:
http://leapsecond.com/pages/gpsdo-sim/

Instead of tweaking GPSDO algorithms or tuning parameters and having to wait days to see if it works or not, the idea was to "replay" pre-recorded 1PPS data and pre-recorded oscillator data into the PLL. This means one can test any new design change in a GPSDO in a matter of seconds instead of days.

So the question is -- could you do the same for NTP? On your own, or with world-wide contributions, you could collect long data sets (phase or frequency) of free-running PC clock oscillators, every shape and size and environment. And then also collect high-precision real-life NTP packet timings, warts and all (especially outlier examples).

Then instead of testing iterations of your new code on live NTP servers you merely apply previously collected packet data and previously collected clock data. With a little scripting you'd get performance plots within seconds instead of waiting hours or days. Moreover, the plots you generate would cover tens or hundreds of historical scenarios instead of just the few you could find in real time.

/tvb




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