Due to the rapidly growing use of networks (LANs, WANs, Internet, etc.) in all segments of commercial, private and government activities, performance management has become an acute problem. In response to this need, a Quality of Service Analyzer that can determine where delays come from, identify ways of reducing these delays, and predict the effects of additional load, is being developed. The QoS Analyzer is founded on a model-based approach that involves automatic calibration to measured data. This approach, which originated in the process control and aerospace industries, has now been adapted to the network management problem. It provides high accuracy for monitoring, as well as predictive calculations. In Phase I, a theoretical framework was developed and a prototype implemented to solve customer problems and demonstrate the benefits of the technology. In Phase II, the underlying technical foundation will be extended. The focus will be on expanding the validity of the developed framework and searching for solutions that can provide specified quality of service. Commercial Applications and other Benefits as described by he awardee: By analyzing and identifying delays in computer networks, this product should improve productivity in both government and commercial markets.