When work using a “cheap” wireless network (yes, I still have kind neighbours), each new ssh connection takes a lot of time, because a new authentication is required from the peer, but what happens if I already connected? In theory no new re-authentication is necessary, you can use existing socket to send data over the same channel of the previous connection. To enable socket manager, put the following lines in your ~/.ssh/config file:
Host * ControlMaster auto ControlPath ~/.ssh/socket-%r@%h:%p
Some situations may freeze your ssh connection, for example when the network goes down before close connection and timeout is reached, in this case the socket will also be frozen, and new connections to the same destination are no possible. Only need to remove the socket file in ~/.ssh/ directory and kill the previous session.