alt Hacker News> I kinda don’t like PTP. Too complicated and requires specialized hardware.
In my view the specialised hardware is just a way to get more accurate transmission and arrival timestamps. That's useful whether or not you use PTP.
> My mental model is that you form a connected graph of clocks and this allows you to convert arbitrary timestamps from any clock to any clock. This is a lossy conversion that has jitter and can change with time.
This sounds like the "peer to peer" equivalent to PTP. It would require every node to maintain state about it's estimate (skew, slew, variance) of every other clock. I like the concept, but obviously it adds complexity to end-stations beyond what PTP requires (i.e. increases the hardware cost of embedded implementations). Such a system would also need to model the network topology, or control routing (as PTP does), because packets traversing different routes to the same host will experience different delay and jitter statistics.
> TicSync is cool
I hadn't seen this before, but I have implemented similar convex-hull based methods for clock recovery. I agree this is obviously a good approach. Thanks for sharing.
> This sounds like the "peer to peer" equivalent to PTP. It would require every node to maintain state about it's estimate (skew, slew, variance) of every other clock.
Well, it requires having the conversion function for each edge in the traversed path. And such function needs to exist only at the location(s) performing the conversion.
> obviously it adds complexity to end-stations beyond what PTP requires
If you have PTP and it works then stick with it. If you’re trying to timesync a network of wearable devices then you don’t have PTP stamping hardware.
> because packets traversing different routes
Fair callout. It’s probably a more useful model for less internty use cases. Of which there are many!
For example when trying to timesync a collection of different sensors on different devices/microcontrollers.
Roboticists like CanBus and Ethercat. But even that is kinda overkill imho. TicSync can get you tens of microseconds of precision in user space.