[lifty]

Indeed. The machines that do the actual work will still use a an inaccurate clock and get periodic corrective updates. That being said, you should be able to get a much higher precision using PTP and some decent network cards. There are plenty of factors that come into play (network latency, congestion, etc) but 7 ms sets the bar low.

[easytiger]

7ms is even achievable with a well done local NTP setup