In contrast to pure video servers, advanced applications such as digital libraries or teleteaching exhibit a mixed workload with massive access to conventional, "discrete" data such as text documents, images and indexes as well as requests for "continuous data". In addition to the service quality guarantees for continuous data requests, quality--conscious applications require that the response time of the discrete data requests stay below some user--tolerance threshold. In our paper, we study the impact of different disk scheduling policies on the service quality for both continuous and discrete data. We identify a number of critical issues, present a framework for describing the various policies in terms of few parameters and finally provide experimental results, based on a detailed simulation testbed, that compare different scheduling policies. 1 Introduction 1.1 Service Quality and Server Architecture for Continuous Data Load Quality of service requirements for "continuous" dat...

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In contrast to pure video servers, advanced multimedia applications such as digital libraries or teleteaching exhibit a mixed workload with massive access to conventional, "discrete" data such as text documents, images and indexes as well as requests for "continuous data", like video and audio data. In addition to the service quality guarantees for continuous data requests, qualityconscious applications require that the response time of the discrete data requests stay below some user-tolerance threshold. In this paper, we study the impact of different disk scheduling policies on the service quality for both continuous and discrete data. We provide a framework for describing various policies in terms of few parameters, and we develop a novel policy that is ex- perimentally shown to outperform all other policies. * This work has been supported by the ESPRIT Long Term Research Project HERMES. to appear in the Special Issue of the Journal of Multimedia Tools and Applications 2 1 Int...

Distributed multimedia presentation systems require high flexibility and good quality of service. To ensure flexible and satisfiable presentations of multimedia data, collaborations between servers, network, and clients must be carefully designed to retrieve the data from the disk and transfer the data to the client. In addition the system must be able to handle interactive requests with minimal latency. However, most of current multimedia data is provided in a compressed form to reduce storage requirements. Data compression techniques introduce burstiness in multimedia data, which complicates buffer and resource management. Current designs lack a uniform transmission support necessary for multimedia presentation systems, which utilize compressed data. In this proposal, we introduce an efficient transmission framework for the NetMedia system. NetMedia is a future novel distributed presentation system, which includes data base management, admission control and graphical inter...