The direct adjustment algorithm: A TCP-friendly adaptation scheme

Abstract

Many distributed multimedia applications have the ability to adapt to fluctuations in the network conditions. By adjusting temporal and spatial quality to available bandwidth, or manipulating the playout time of continuous media in response to variations in delay, multimedia flows can keepan acceptable QoS level at the end systems. In this study, we present a scheme for adapting the transmission rate of multimedia applications to the congestion level of the network. The scheme called the direct adjustment algorithm (DAA), is based on the TCP congestion control mechanisms and relies on the end-to-end Real Time transport Protocol (RTP) for feedback information. Our investigations of the DAA scheme suggest that simply relying on the the TCP-throughput model might result under certain circumstances in large oscillations and low throughput. However, DAA achieves, in general, high network utilization network and low losses. Also, the scheme is shown to be fair towards competing TCP traffic. However, with no support from the network, long distance connections receive less than their fair share.