Comparison of the use of different ECN techniques for IP multicast congestion control

We have recently proposed the use of backward explicit congestion notification (BECN) with video multicasting over IP networks. This proposal improved bandwidth utilization and reduced time to react to congestion. In this paper, we present a comparison of the use of different ECN techniques, namely ECN, BECN, and MECN, for IP multicast congestion control. We investigate this in the context of MPEG4 multicasting over IP. We use these ECN techniques in an IP network that supports priority dropping of packets during congestion using RED's extension for service differentiation. This extension recognizes the priority of packets when they need to be dropped and drops lower priority packets first. ECN techniques provide early notification to the sender and/or the receivers about congestion while it is developing in the network. Based on which ECN technique is used, the sender and/or the receivers react to this notification to reduce the congestion in the network. We show the advantages and disadvantages of each ECN technique. Also, through the results, we advocate the use of network support in the form of explicit congestion notification for IP multicast congestion control.