The Issue of Useless Packet Transmission for Multimedia over the Internet Jim Wu * , Mahbub Hassan School of Computer Science & Engineering The University of New South Wales Sydney 2052, Australia Abstract When packet loss rate exceeds a given threshold, received audio and video become un- intelligible. A congested router transmitting multimedia packets, while inflicting a packet loss rate beyond a given threshold, effectively transmits useless packets. Useless packet transmission wastes router bandwidth when it is needed most. We propose an algorithm to avoid transmission of useless multimedia packets, and allocate the recovered bandwidth to competing TCP flows. We show that the proposed algorithm can be easily implemented in well-known WFQ and CSFQ fair packet queueing and discarding algorithms. Simula- tion of a 15-second MPEG-2 video clip over a congested network shows that the proposed algorithm effectively eliminates useless packet transmission, and as a result of that signif- icantly improve throughput and file download times of concurrent TCP connections. For the simulated network, file download time is reduced by 55% for typical HTML files, 36% for typical image files, and up to 30% for typical video files. A peak-signal-to-noise-ratio (PSNR) based analysis shows that the overall intelligibility of the received video is no worse than that received without the incorporation of the proposed useless packet trans- mission avoidance algorithm. Our fairness analysis confirms that implementation of our algorithm into the fair algorithms (WFQ and CSFQ) does not have any adverse effect on the fairness performance of the algorithms. Key words: TCP, multimedia over IP, MPEG-2, Internet, Fair Packet Queueing Algorithm. * Corresponding author. Email addresses: jimw@cse.unsw.edu.au (Jim Wu), mahbub@cse.unsw.edu.au (Mahbub Hassan). Preprint submitted to Elsevier Science 8 November 2002