End-to-End Performance of Web Services

As the number of applications that are made available over the Internet rapidly grows, providing services with adequate performance becomes an increasingly critical issue. The performance requirements of the newapplications span from fewmilliseconds to hundreds of seconds. In spite of the continuous technological improvement (e.g., faster servers and clients, multi-threaded browsers supporting several simultaneous and persistent TCP connections, access to the network with larger bandwidth for both servers and clients), the network performance as captured by response time and throughput does not keep up and progressively degrades. Several are the causes of the poor "Quality of Web Services" that users very often experience. The characteristics of the traffic (self-similarity and heavy-tailedness) and the widely varying resource requirements (in terms of bandwidth, size and number of downloaded objects, processor time, number of I/Os, etc.) of web requests are among the most important ones. Other factors refer to the architectural complexity of the network path connecting the client browser to the web server and to the protocols behavior at the different layers.In this paper we present a study of the performance of web services. The first part of the paper is devoted to the analysis of the origins of the fluctuations in web data traffic. This peculiar characteristic is one of the most important causes of the performance degradation of web applications. In the second part of the paper experimental measurements of performance indices, such as end-to-end response time, TCP connection time, transfer time, of several web applications are presented. The presence of self-similarity characteristics in the traffic measurements is shown.

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