Research On Efficiency And Fairness For Congestion Control

The end-to-end congestion control mechanism plays an important role in guaranteeing the robustness of the Internet. But the efficiency of this mechanism rely on two preconditions, the network traffics are responsive and TCP-friendly. With the growth of Internet, there are more and more stream media and multicast traffics appear on the Internet. Because of the technical difficulty, most of them don't use any congestion control mechanism. This situation raise the possibility of congestion occurs, and threaten the robustness. In this situation, on one hand, we should make the network itself can work effective in spite of there are abnormal traffics, on the other hand, we should propose more effective and more fair congestion control mechanism for those stream media and multicast traffics. Only the two sides work together, the Internet congestion problem can be solved effectively.A novel AQM algorithm LQC (Load Queue Control) that uses both traffic load and queue length to indicate congestion degree was proposed in this paper to decrease the possibility of congestion occurring on the network aspect when there are abnormal traffics. In this algorithm, traffic load and queue length was effectively combined to indicate the congestion degree, and the incoming packet is dropped according the time in which the queue is supposed to be full. Through simulation on NS-2, the algorithm was proved can control the queue length effectively and keep the end-to-end throughput on a high level. On the end-to-end aspect, A novel stream media multicast congestion control algorithm SMCC(Stream media Multicast Congestion Control) was proposed in this paper to solve the congestion caused by the stream media multicast traffic. Aim to solve the scalability and TCP-friendly problem which most of the existing algorithm have, we extend the thought of ECN and XCP (a newly proposed protocol believed to be superior to TCP) to stream media multicast transport applications, propose a router-aided layered stream media multicast congestion control algorithm. By defining a new congestion header, sender tell the router the rate and control period information, then the router count the throughput indicator information according to the link status, set it to the congestion header and forward it to the receiver. Finally, the receivers decide to join or leave some layers by anglicizing the congestion header so as to react to the network status. Through router feed forward the throughput indicator to the receiver, this mechanism avoids the scalability problems caused by feed back system and uses the link bandwidth effectively and fairly. Simulation on NS-2 shows that the mechanism can fit heterogeneous network well and makes the multicast stream traffics share the bottleneck with TCP traffics more fairly.