Connections

TCP Keepalive Probes Detect Dead Idle Connections

A TCP connection can remain established even when no application data is moving. That is useful for database sessions, remote shells, messaging links, and other services that may stay quiet for long periods. Silence also creates an awkward case. A peer can lose power, move to another network, or disappear behind a failed path without sending a TCP FIN or RST. The other endpoint may retain an established connection because it has received no packet proving that the path is gone.