An architecture for adaptive QoS and its application to multimedia systems design

We describe a prototype implementation of a distributed multimedia system that generalizes the concept of QoS to all layers of its software architecture. Each layer deals with QoS at its appropriate level of abstraction using a generic API for communicating QoS parameters and values to layers above and below. The aggregation of these parameters and values is called a service contract. This architecture provides a hierarchical framework to design adaptive multimedia systems. Furthermore, the API allows for reporting of contract violations as well as dynamic renegotiation of the contract terms. A proof-of-concept multimedia system was built to evaluate the proposed architecture. Key components of this system are: a graphical user interface that dynamically requests the quality expected by the user to lower level components, a dynamic network service that efficiently matches network resources to user requirements and a processor scheduler which schedules tasks according to their execution requirements. Our experience with this system showed that the proposed architecture is an efficient framework for building adaptive multimedia systems. (C) 1998 Elsevier Science B.V.