netipv4tcpkeepaliveprobes

netipv4tcpkeepaliveprobes is a kernel parameter in Linux that controls the number of unacknowledged probe segments that a TCP connection will send before considering the connection dead. These probe segments are part of the TCP Keepalive mechanism, which is designed to detect and clean up idle, broken connections. When Keepalive is enabled, the system periodically sends small TCP packets to the other end of an established connection. If no response is received after a certain number of probes, the connection is considered to be no longer active and is closed by the kernel.

The value of netipv4tcpkeepaliveprobes determines how aggressive the system is in detecting dead connections. A higher value means that the system will wait longer and send more probes before giving up on a connection. Conversely, a lower value will result in quicker detection of broken connections. The default value in most Linux distributions is typically set to a reasonable number that balances responsiveness with avoiding premature disconnection of legitimate but idle connections.

This parameter is part of a suite of TCP Keepalive settings, which also include netipv4tcpkeepaliveintvl (the interval between probes) and netipv4tcpkeepalivetime (the time of inactivity before the first probe is sent). Administrators may adjust these values to fine-tune how their systems handle network connections, particularly in environments with potentially unreliable networks or long-lived idle sessions. Modifying these parameters requires root privileges.