The paper investigates a modified version of an active buffer management scheme, "jitter detection" (JD), for gateway-based congestion control to stream layered multimedia multicast traffic over IP networks. The JD scheme works well with traditional congestion control schemes, such as RED, which are used for non-multimedia traffic. At the same time, the JD scheme improves the quality of service in multimedia networking by detecting and discarding useless packets that accumulated large enough jitter, in order to maintain a high bandwidth for packets within the jitter tolerance of the multimedia player. The paper also considers multicast with a layered coding scheme for multimedia streaming quality improvement. Differentiated from the traditional JD scheme, we propose to preserve the base layer traffic with best effort when passing through the gateway. The priority of dropping decisions is given to those higher level layer (enhancement layer) multicast packets. Queuing analysis has been performed to evaluate the efficiency of the proposed scheme. Simulations by NS2 were also performed and the results show that the proposed scheme can provide better quality than that using RED in gateway-based congestion control for multimedia traffic.
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