A quality of service negotiation procedure for distributed multimedia presentational applications

Most current approaches in designing and implementing distributed multimedia (MM) presentational applications have concentrated on the performance of the continuous media file servers in terms of seek-time overhead and real-time disk scheduling; particularly, the quality of service (QoS) negotiation mechanisms they provide are used in a rather static manner, i.e. these mechanisms are restricted to the evaluation of the capacity of certain system components. In contrast to those approaches, we propose a general QoS negotiation framework that supports the dynamic choice of a configuration of system components to support the QoS requirements of the user of a specific application: we consider different possible system configurations and select an optimal one to provide the appropriate QoS support. We document the design and implementation of a QoS negotiation procedure for distributed MM presentational applications, such as news-on-demand. The negotiation procedure described is an instantiation of the general framework for QoS negotiation. Our proposal differs in many respect with the negotiation functions provided by existing approaches: (1) the negotiation process uses an optimization approach to find a configuration of system components which supports the user requirements, (2) the negotiation process supports the negotiation of a MM document and not only a single monomedia object, (3) the QoS negotiation takes into account the cost to the user; (4) the negotiation process may be used to support automatic adaptation to react to QoS degradations, without intervention by the user/application.