The signal-to-noise ratio would be a nuisance, naturally, but there's a more fundamental problem that's stopped anyone from trying this. Internet routing and la

The signal-to-noise ratio would be a nuisance, naturally, but there's a more fundamental problem that's stopped anyone from trying this. Internet routing and latency is asymmetric - your request to the time server will, in general, go via a different route that takes a different amount of time compared to the message back. This introduces a bias that is indistinguishable from local clock error. Without precisely synchronised clocks at both ends, you can only determine the overall round-trip time and not the time each leg took, and therefore you cannot calculate the exact difference between your local clock and the server. This is an inhererent limit on how accurate NTP can be over the Internet. (The other reason not to bother is that GPS is cheap and can provide a very accurate synchronized clock source over long distances.)