The default minimum retransmission time-out (RTO) value in milliseconds. The calculated RTO for all TCP connections cannot be lower than this value. See also tcp_rexmit_interval_max.
1 millisecond to 20 seconds
Do not change the value in a normal network environment.
TCP's RTO calculation should be able to cope with most RTT fluctuations. If in some very special circumstances such that the round trip time (RTT) for a connection is in the order of 10 seconds, change to a higher value. If you change this value, you should change the tcp_rexmit_interval_max parameter to match it. You should change the value of tcp_rexmit_interval_max to at least eight times the value of tcp_rexmit_interval_min.