RACCOOM: a rate-based congestion control approach for multicasts
Yuan Gao, Jennifer C. Hou, Sanjoy Kumar Paul · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2001
As continuous media multicast applications become widely deployed on the Internet, it becomes increasingly important to ensure these applications respond to network congestion in a TCP-friendly manner so as to coexist with TCP connections (which constitutes the majority of the Internet traffic). In this paper, we present a RAte-based Congestion COntrOl scheme for Multicasts, called RACCOOM, for continuous media multicast applications. In the absence of packet loss, a RACCOOM session keeps track of the congestion status of the on-tree path with the largest round trip time (called the target path), and adjusts its sending rate using a TCP Vegas-like method. RACCOOM is also equipped with mechanisms to deal with changes of the target path due to traffic change and member join/leave. Upon detection of packet loss anywhere in the multicast tree, RACCOOM then responds by reducing its sending rate by half in a TCP-Reno manner. The ACK aggregation method used in RACCOOM prevents ACK implosion and yet provides the sender with a simple but comprehensive view of congestion conditions in the multicast tree. To achieve TCP-friendliness, we have devised a simple method in RACCOOM to on-line adjust the parameters of its rate adjustment method. Alternatively, we can achieve (weighted) fairness among competing RACCOOM connections by tuning its parameters using results obtained from the control feedback theory. We validate the design, and demonstrate the features, of RACCOOM in ns-2. The encouraging simulation results coupled with the fact that all the RACCOOM operations can be performed at end hosts, suggest that RACCOOM is a practical, and yet effective congestion control solution for continuous media multicast applications.