rack_get_measure_window
tp->gput_ack = tp->gput_seq + rack_get_measure_window(tp, rack);
tp->gput_ack = startseq + rack_get_measure_window(tp, rack);
if ((rack->r_ctl.rc_first_appl->r_end - th_ack) >= rack_get_measure_window(tp, rack)) {
tp->gput_ack = tp->gput_seq + rack_get_measure_window(tp, rack);
tp->gput_ack = tp->gput_seq + rack_get_measure_window(tp, rack);
ideal_amount = rack_get_measure_window(tp, rack);