[huntero]

PTP is a great choice when you need your time-sync to leave the software domain, for instance, locking an external PLL for frequency and phase aligned clocks.

PTP enabled MAC's and PHY's usually have a dedicated hardware output for a PPS (pulse-per-second) or faster clock, generated directly from the hardware PTP counters.

In the video world, we get great results synchronizing software events with NTP, but whenever you jump to a physical interface (DisplayPort, HDMI, SDI, etc.), NTP-based clocks are far too jittery.

I've seen some work using the PTP hardware in the MAC with the NTP protocol, a sort of hybrid approach, but don't have any first hand experience.