Research On IP Multicast Congestion Control Algorithms

Multicast is a new network technology in Internet, it can save much bandwidth by transmitting Multimedia Data, such as videoconference and remote teaching. So it is considered as an efficient means to resolve the communication problems of point-to-multipoint. But multicast based on UDP cannot offer congestion control. At the present time,that existing TCP applications,as the main applications in the Internet, offer congestion control have made it important to ensure the fairness when multicast coexists with TCP protocols. Therefore the research on multicast congestion control is becoming an important subject.The principle based on receiver-driven layered multicast congestion control is that the sender only sends data at a fixed rate, and the receivers receive data at a fitting rate according to the present congestion statue. This paper analyzes the existing problems based on the receiver-driven layered multicast congestion control at present. Facing these questions ,it presents a improved receiver-driven layered multicast congestion control algorithm—IRLMCC (Improved Receiver-driven Layered Multicast Congestion Control).Firstly, this multicast congestion control algorithm adjusts and alternates receiving rate by GAIMD algorithm so as to avoid congestion. GAIMD algorithm emulates AIMD algorithm, which have been widely used in TCP protocols. It can ensure the fairness when multicast coexists with TCP protocols. By adjusting parameters, it can enhance the system's responding speed under the condition of TCP friendly.Secondly, this paper presents a mechanism of congestion signal detection without feedback implosion. So this algorithm enlighten the sender's burdens , at the same time, it make the protocols more simple and scalable.Finally, NS2, a widely used network simulation tool, is used to analyze and validate the performance of algorithms on the aspects of fairness,throughput,scalable and so on.