Congestion Control Scheme for Reliable Multicast Improving Intra-Session Fairness with Network Support

In reliable multicast communications, data packets are disseminated to all receivers in a multicast group. Generally, end-to-end congestion control adjusts transmission rate of the sender to the node of the lowest throughput in a multicast group. In this situation, when a multicast group includes receivers of significantly low throughput, lots of receivers suffer throughput degradation due to existence of low throughput nodes. This technical problem, called intra-session fairness, is special problem for multicast communications which include lots of receivers whose receiving capability is different in general. This paper proposes a new congestion control scheme for reliable multicast which improves intra-session fairness. A proposed scheme makes use of network support technology to enable a server in a network which includes low throughput receiver beneath it to behave as a pseudo receiver. A server stores arrived data packets and transmits them to receivers beneath it with adjusting transmission rate to the lowest throughput one. A server can hide existence of low throughput nodes to the sender, which enables improvement of intra-session fairness. Simulation results show that our proposed congestion control scheme improve intra-session fairness with increase of servers. We also show strategic arrangement of servers brings better improvement of intra-session fairness with small number of servers.