On-board processing (OBP) is one of significant satellite communication technologies, and the Asynchronous Transfer
Mode (ATM) is widely used in the OBP which can guarantee the QoS. This article presents the CAC (Call Admission
Control) algorithm and Congestion Control algorithm. We combine with B-CAC algorithm, Bahadur-Rao's theory, Weiss
theory, to improve the old method, and the simulation results show that when the PDR/LR is small the burst is high, the
chain utilization and statistic multiplexing gain get a big advantage. Besides, concerning TCP congestion control, the
article compared five strategies: Tahoe, Reno, Newreno, Sack and Vegas. The simulation results show that the Vegas can
be used to predict congestion conditions correctly; its congestion window (cwnd) control is smoother and is superior to
other algorithms in average RTT.