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.