Specifies whether the system should send keepalive messages to the other side. If they are sent, death of the connection or crash of one of the machines will be properly noticed. However, this means that connections will die if the route is down temporarily, and some people find it annoying. On the other hand, if keepalives are not send, sessions may hang indefinitely on the server, leaving ``ghost'' users and consuming server resources.
The default is ``yes'' (to send keepalives), and the server will notice if the network goes down or the client host reboots. This avoids infinitely hanging sessions.
To disable keepalives, the value should be set to ``no'' in both the server and the client.