Avoiding useless multimedia packet transmission over DiffServ networks with multiple bottlenecks

Useless packet transmission (UPT) arises when a multimedia stream becomes unintelligible because too many packets, in aggregate, are dropped by fair queuing algorithms at routers, even with low drop rates at individual routers. We propose two UPT avoidance (UPTA) schemes for networks with multiple congested links: partial UPTA (P-UPTA), which is core-stateless, and centralized UPTA (C-UPTA), which employs a bottleneck fairshare discovery (BFD) protocol to determine a flow's global fairshare. Our simulation study shows that P-UPTA eventually detects UPT, but bandwidth may be wasted on upstream links before UPT is detected, whereas C-UPTA avoids UPT in all situations as it always drops useless packets at the network edge. We quantitatively analyse the performance of C-UPTA in conjunction with WFQ, in terms of TCP throughput, file download time, MPEG-2 video intelligibility, and fairness. The results reveal that, for the scenarios simulated, the TCP throughput is improved by up to 50% without any significant impact on the intelligibility of the MPEG-2 video and the fairness of the scheduling algorithm.