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IP multicast over the unidirectional satellite network provides a low cost and effective one-to-many communication solution with wide area coverage. However, for distributing software or large amount of textual information over the network, we need the multicast protocol to provide data reliability. In this talk, we present a reliable multicast protocol which is suitable for unidirectional satellite link, called Reliable Multicast over Unidirectional Link (RMU). We assume highly asymmetric bandwidth capacities with high bandwidth satellite downlink and low bandwidth on the terrestrial return path. For error control, RMU ensures data reliability by having the receiver detect packet loss and report that to the sender. From the data loss information collected, the sender uses selective repeat algorithm to retransmit data through the multicast group. RMU minimizes acknowledgement process to avoid congestion on the return path and also keeps the sender away from ACK implosion. As for congestion control, RMU monitors the current condition of the network and adjusts the data rates accordingly. Our experimental results show that RMU provides reliable transmission and effectively utilizes available bandwidth as compared to TCP and another MBFC flow control schemes.
In this talk, we will describe an application in web content distribution where we push popular cache objects to member proxies based on scheduled delivery timetable. The muliticast push component co-exist with the normal on-demand hierachical cache system which fetches objects based on user requests.
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