My understanding is that PTP is neither necessary nor sufficient. The main advantage of it is that some hardware will only support adding hardware timestamps to

My understanding is that PTP is neither necessary nor sufficient. The main advantage of it is that some hardware will only support adding hardware timestamps to PTP messages (ie you want to use the time packets left/arrived at your network card rather than the time you processed them in the kernel/userspace). But I think the specialness of PTP can lead to dealing with a lot of bugs from bad implementations.