<snip lots of detail> > So, the summary is that drift goes to 500ppm when stepping is disabled > but runs normally when stepping is enabled and both situations never > require a time step. This makes no sense to me. By the way, as > mentioned previously, we require that time does not step backward due to > a problem in some commercial software that cannot currently tolerate > time moving backwards. > > Quite frankly, I don't think it's unreasonable that a system require > time to monotonically increase.
Forgive me if this answer misses a point in the earlier details, or shows my ignorance of NTP, but a few ideas/thoughts. Oscillators and drift can go in either direction, fast or slow, its a physics-based situation. You can't write code around that and provide a software solution that is monotonic at all times. However, a single negative step just at the start may be required before going monotic after that event. (Not an expert, but that is my understanding). With this ref clock and a GPS-drive IRIG source, you may only see a single negative step when NTP first begins running on a new system with no drift file, or a system that has been powered off a long time with a battery-driven clock drifting over that long time. Once NTP is humming along after the initial step and some updates, you shouldn't see a step again. This makes me think that you should insert a delay in launching your sensitive application, or block the application at some point, so it does not see the (possible) first time step. Fran Horan JHU/APL _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
