End-To-End Quality of Service Control Using Adaptive Applications

Many distributed multimedia applications exhibit flexibility to fluctuations in the network conditions. By trading off temporal and spatial quality to available bandwidth, or manipulating the playout time of continuous media in response to variations in delay, multimedia flows can keep an acceptable QoS level at the end systems. In this study, we present a new scalable scheme for adapting the transmission rate of multimedia applications to the congestion level of the network. The scheme is based on the end to end real time transport protocol (RTP). Using the proposed scheme, we investigate the efficiency of applying adaptation in utilizing network resources, reducing losses and the scalability of the scheme as well as that of the RTP protocol. The results obtained through simulations suggest the efficiency of the scheme in utilizing the network resources and decreasing the loss rates. Keywords Direct adjustment algorithm, adaptive applications, RTP, RTCP, scalability. 1 INTRODUCTION ..

The Direct Adjustment Algorithm: A TCP-Friendly Adaptation Scheme

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 keepa n 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

Constrained TCP-Friendly Congestion Control for Multimedia Communication

With the lack of admission control and resource reservation mechanisms in the Internet, overload situations can only be avoided by having the end systems deploying congestion control schemes. That is, the end systems should adjust their transmission and reception behavior in accordance with the available network resources. This is generally achieved by adjusting the transmission behavior of a sender based on feedback information from the receiver about the network congestion situation. Current proposals for rate adaptation assume that the sender can adjust its transmission with arbitrary granularity. However, especially for the case of audio and video communication it is often the case, that the used compression style, application or the user might impose strict limitations as to the maximum and minimum transmission rates, the granularity with which the sender can change its transmission rate and the frequency with which such changes should occur. In this paper, we present a..