MLDA: A TCP-friendly Congestion Control Framework for Heterogeneous Multicast Environments

To avoid overloading the Internet and starving TCP connections, multimedia flows using non-congestion controlled UDP need to be enhanced with congestion control mechanisms. In this paper, we present a general framework for achieving TCP-friendly congestion control called MLDA. Using MLDA, multimedia senders adjust their transmission rate in accordance with the network congestion state. For taking the heterogeneity of the Internet and the end systems into account, MLDA supports layered data transmission where the shape and number of the layers is determined dynamically based on feedback information generated by the receivers. Further, we discuss a measurement approach that allows receivers in large multicast sessions to estimate the round trip delay estimation to the sender in a scalable way. For exchanging control information between the sender and receivers we investigate the possibility of using the real time transport protocol (RTP) and discuss the required changes in order for RTP to support a more scalable and timely flow of feedback information from the receivers to the sender. Results obtained through simulations and measurements as well as comparisons to other congestion control schemes suggest that MLDA achieves TCP-friendly congestion control on the one hand and its ability to accommodate the needs of heterogeneous receivers on the other.