Solaris Tunable Parameters Reference Manual



This ndd parameter sets a probe interval that is first sent out after a TCP connection is idle on a system-wide basis.

Solaris supports the TCP keep-alive mechanism as described in RFC 1122. This mechanism is enabled by setting the SO_KEEPALIVE socket option on a TCP socket.

If SO_KEEPALIVE is enabled for a socket, the first keep-alive probe is sent out after a TCP connection is idle for two hours, the default value of the tcp_keepalive_interval parameter. If the peer does not respond to the probe after eight minutes, the TCP connection is aborted. For more information, refer to tcp_keepalive_abort_interval.

You can also use the TCP_KEEPALIVE_THRESHOLD socket option on individual applications to override the default interval so that each application can have its own interval on each socket. The option value is an unsigned integer in milliseconds. See also tcp(7P).


2 hours


10 seconds to 10 days


Unsigned integer (milliseconds)



When to Change

Do not change the value. If under special circumstances, the first keepalive probe needs to be sent earlier than two hours, use the TCP_KEEPALIVE_THRESHOLD socket option to reduce the interval on an individual application.

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