[jhellan]

Basically, PTP assumes that network delays are deterministic. If that's true, it is very precise. If not, PTP is the wrong tool. NTP assumes that network delays are stochastic, and uses sophisticated algorithms to account for this. PTP has much simpler algorithms, which can be implemented in electronics, where internal timings can be characterized. NTP is more complex, and tends to run on a general purpose computer. This adds internal OS timings to the uncertainty.