Issue No. 12 - December (2003 vol. 52)
Jennifer C. Hou , IEEE
Sanjoy Paul , IEEE
<p><b>Abstract</b>—As multicast applications have become widely deployed on the Internet, it is increasingly important to ensure these applications respond to network congestion in a TCP-friendly manner so as to coexist with TCP connections (which constitute the majority of the Internet traffic). In this paper, we present a RAte-based Congestion COntrOl scheme for Multicast, called <it>RACCOOM</it>, for applications that deploy source-based multicast trees as the communication paradigm. In the absence of packet loss, a <it>RACCOOM</it> session keeps track of the congestion status of the on-tree path with the largest round trip time (called the <it>target</it> path) and adjusts its sending rate using a TCP Vegas-like method. Upon detection of packet loss anywhere in the multicast tree, <it>RACCOOM</it> then responds by reducing its sending rate by half in a TCP-Reno manner. The ACK aggregation method used in <it>RACCOOM</it> prevents ACK implosion and yet provides the sender with a simple but comprehensive view of congestion conditions in the multicast tree. Finally, <it>RACCOOM</it> is equipped with mechanisms to deal with changes of the target path due to traffic change and member join/leave. To achieve TCP-friendliness, we have devised a simple method in <it>RACCOOM</it> to emulate how a TCP connection would behave under the same packet loss and delay characteristics. The results thus derived are used by <it>RACCOOM</it> to online adjust the parameters of its rate adjustment method. Alternatively, we can achieve (weighted) fairness (in terms of bandwidth sharing) among competing <it>RACCOOM</it> connections based on results obtained from feedback control theory. We validate the design, and demonstrate the features, of <it>RACCOOM</it> in ns-2. The encouraging simulation results, coupled with the fact that all the <it>RACCOOM</it> operations except acknowledgment aggregation (which requires modest router support) can be performed at end hosts, suggest that <it>RACCOOM</it> is a practical and yet effective congestion control solution for multicast applications.</p>
Rate-based congestion control, multicast, feedback control, TCP friendliness, weighted fairness, performance evaluation.
J. C. Hou, S. Paul and Y. Gao, "RACCOOM: A Rate-Based Congestion Control Approach for Multicast," in IEEE Transactions on Computers, vol. 52, no. , pp. 1521-1534, 2003.