parameter sets the values of \fIidle\fP, \fIprobes\fP, and \fIinterval\fP
used to check whether a socket is alive;
.I idle
-is the number of seconds a connection needs to remain idle before TCP
+is the number of seconds a connection needs to remain idle before TCP
starts sending keepalive probes;
.I probes
is the maximum number of keepalive probes TCP should send before dropping