How to synchronize frame updates across a network of multiple (UDP) clients?

So basically, I am creating a server/client UDP multicast system where the server sends packages with update information (for now only an X position) which needs to be synchronous updated across all connected clients. The problem which came across is that running the application on each client PC of course does not guarantee updates that are happening at the exact same time. Could anybody here point me in the right direction?

Every solution I tried to implement fell back to using the Unity Update loop, which is not reliable since I don’t know if on the exact time the frame is being updated, all the other client PC’s are updating as well. (To give you some more information, right now there are two custom screens next to eachother, they are showing irregularly sometimes frame offsets, not because of the network, but because of the frame timing I suppose.)

Wishing you all a good weekend! :)

Keywords: UDP, Networking, frame update, frame synchronization, exact synchronization

edit: wanted to wish you all a good weekend.