Some principles for quality of service management

Distributed multimedia applications require a variety of levels of quality of service (QoS) from communication networks and end-systems which realize the multimedia interface with the human users or provide remotely accessed multimedia information. The management of these services has to take into account the available resources and the user's wishes concerning the desired quality and costs. Based on our experience with the construction of a News-on-Demand prototype, we present in this paper a few simple principles applying to QoS management for distributed multimedia applications. We discuss in particular ways in which an application can adapt to reduced network performance related to throughput, loss, delay or jitter, and we consider the situation where the configuration of the distributed application can be selected dynamically and be revised during the running of the application. We also comment on the handling of QoS in a layered system architecture and the use of performance models for QoS management.