Who constantly keeps numerous SSH connections open knows the problem. If you in a compound just not as active as it can happen that the connection breaks off. The reason for this are usually SSH-setting of the client and the SSH server. These detect some “inactivity” (no traffic on the lines going) and end the session.
To prevent this, there is a SSH option named keep-alive specifically located in
/etc/ssh/ssh_config and is called:
The interval refers to seconds. In this case, every 5 seconds a keep-alive through the SSH tunnel shipped to signal an activity.