The Implication of Network Performance on Service Quality

As the Internet infrastructure evolves to include Quality of Service (QoS), it is necessary to map application quality requi rements to network performance specifications in terms of delay and loss ra te. In this paper, we first propose a new testbed by using a combination of si mulation and emulation technics. Next, we use this testbed in studyin g the effect of network performance metrics on the perceptual quality of various applications to demonstrate the applicability of the testbed. We ex amine two typical applications on the basis the new testbed: the World Wide Weband the Internet Telephony. In our study of the World Wide Web, we derived a new TCP short connection model that computes the latency of Web r etrieval accurately and efficiently given only the packet delay and loss rate characteristics apriori. In the study of Internet telephony, we show that the packet delay variance is the dominant network characteristics which aff ect the perceptual quality. As a result, the service quality drops dramatically when the network offered load reaches80%. This can serve as a guideline for studies towards improving service quality of Internet telephony.

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