The client and server keep exchanging ping packets every 5 seconds. If no reply is received in 10 seconds, the client or server will print a warning in the session log. This warning has the form “No data received since…”. If you don’t see these logs, this means that client and server are communicating fine and the network is not the problem. Additionally, when no communication is possible, you should see the client screen ghosting until the communication is restored. If the duration of the freeze is shorter than 10 second, though, you won’t see anything in the logs. But this doesn’t mean that a freeze of 1 or 2 seconds is less annoying. What we want to rule out is that it is a NoMachine problem and not a network problem. If you see the logs, it’s for sure a network problem. If you don’t see the logs, it may be still a network problem but of a different kind, involving the available bandwidth.
Consider that the quality of the link is extrememly important for this kind of applications. It is not a matter of bandwidth (every residential customer having a ADSL link has enough bandwidth to run NoMachine comfortably) and not even latency (although the lowest it is, the best will be the user experience, with also a round-trip time >50 ms becoming noticeable). For quality of the link I mean the ability of the ISP to give to all users a equal share of the network, something current ISPs are very bad at doing. So all it takes is a user on the same network segment that starts a bittorrent download to cause a network congestion and packet retransmission that can take seconds to settle down.