Towards Automatic Trading of QoS Parameters in Multimedia Distributed Applications

摘要

Several existing and emerging studies exhibit demands for the definition, measuring, testing, and enhancement of QoS. Since real-time multimedia applications require guaranteed performance services or graceful degradation services, many problems are particularly complex. ODP considers QoS aspects embedded within the trading function. Emerging systems portray particular service parameters, which must be considered by an ODP trader. The advent of multimedia leads to new functional services (guaranteed, predictive), new management services (QoS management, synchronization management), new protocols (negotiation, re-negotiation), and new mechanisms (parameter translation, parameter matching). This paper deals with the matching function and particular trading aspects in multimedia distributed applications. In order to offer a more flexible matching and reduce the negotiation dialog, we propose a formal model for service parameters, defining special parameter fields. Each new feature is analysed across multimedia examples, its particularities, its value space, and the customer-provider issues related to it. Based on this model, a precise definition of the matching function which is useful to automate the negotiation of QoS is proposed. An algorithm implementing this function is analysed. A model for the evaluation of contractual QoS at the parameter and service level, and specific formulas are presented.