ETFRC: Enhanced TFRC for Media Traffic over Internet

The evident increase in media traffic over Internet is expected to worsen its congestion state.TCP-friendly rate control protocol TFRC is one of the most promising congestion controltechniques developed so far. TFRC has been thoroughly tested in terms of being TCP-friendly,responsive, and fair. Yet, its impact on the visual quality and the peak signal-to- noise ratio PSNRof the media traffic traversing Internet is still questionable. In this paper we aimed to point out theenhancements required for TFRC that enables producing the maximum PSNR value for Internetmedia traffic. Firstly, we suspected the default value of n that represents the number of lossintervals used in calculating the loss event rate in the TFRC equation. This value isrecommended to be set to 8 according to the latest RFC of TFRC. We investigated the effect ofmodifying the TFRC mechanism on the resulting PSNR of the transmitted video over Internetusing TFRC via switching n across the values from 2 to 16. We investigated the effect of suchvariation over a simulated network environment to study its effect on the resulting PSNR for anumber of arbitrary video sequences. Our simulations results showed that running TFRC withn=11 led to reaching the maximum PSNR values among all the examined values of n including itsdefault value. Secondly, we tested the impact on the PSNR of another modification in the TFRCmechanism via switching both values of n and Nfb which is frequency of feedback messages sentby TFRC receiver to its sender every round-trip time RTT. The default value of Nfb is 1; hence wescanned every possible combination of n and Nfb ranging from 2 to 16, and from 1 to 4,respectively and recorded the produced PSNR. It was obvious that several other combinations ofn and Nfb produced higher PSNR values other than their default values in the request forcomment RFC of TFRC. We hereby suggest using an enhanced TFRC that we abbreviated asETFRC which has the values of n and Nfb value set to 4 and 11 respectively as a replacement forthe traditional TFRC to enable reaching higher PSNR for media traffic over Internet.