Abstract: In satellite networks featuring asymmetric bandwidth, the bandwidth of reverse (earth-to-satellite) links is narrow, and congestion is more likely to occur in these links. Congestion occurring in a reverse link is alleviated by decreasing the send window at the sending end, during which, however, the throughput of forward (satellite-to-earth ) links in the network is also lowered. Vegas_FD, a TCP Vegas forward congestion control algorithm based on forward direction delay, is proposed so as to tackle the foregoing problems. The proposed algorithm judges whether a communication link is congested or not by measuring the forward direction delay time of data packets, and adopts different control strategies as per different congestion types of the communication link, so as to ensure that the congestion control algorithm could keep a high throughput when the reverse link is congested. With these functions, the algorithm is adapted to the asymmetry of the satellite network’s bandwidth. The simulated results based on Opnet software show that Vegas_FD algorithm is used to improve remarkably the throughput in satellite networks compared to Vegas and Westwood algorithms. Key

Key words: statellitenetwork, congestioncontrol, spacecommunicationprotocolspecificationtransferprotocol, TCPVegasalgorithm