A reliable multicast protocol for unidirectional satellite link

IP multicast over a unidirectional satellite network provides a low cost solution that provides effective one-to-many communication with a wide area of coverage. However, IP multicast does not provide reliable data transfer which makes it unsuitable for distributing software or a large amount of textual information over the network. We propose a reliable multicast protocol which is designed specifically for a unidirectional satellite link, called reliable multicast over unidirectional satellite link (RMUS). In our design, we consider characteristics of the unidirectional satellite link with long latency delays and often with high bandwidth on the downstream link but narrow return paths. RMUS provides error and congestion control to multicast transmission. RMUS ensures data reliability by having the receivers detect packet loss and report it to the sender. The sender collects data loss information and uses a selective repeat algorithm to retransmit loss packets. RMUS minimizes the acknowledgement process in order to protect the return path from congestion and also to protect the sender from ACK implosion. As for congestion control, RMUS monitors the current condition of the network and adjusts the transmission rate accordingly. The data rate adjustment is designed to effectively utilize the available bandwidth without causing network congestion. Our experimental results show that RMUS provides reliable multicast communication and effectively utilizes the available bandwidth compared to other flow control schemes.