TCP_RTT_SCALE
tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
i = tp->t_srtt * (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
printf("%8.3f ", (double)tp->t_srtt * 1000.0 / TCP_RTT_SCALE / clockinfo.hz);