While increasing bandwidth might be an acceptable way to maximize user utility, it is not always sufficient. This chapter presents a three-layer model of networked multimedia application based on a division into network, application, and usage. Quality measures for each layer are presented. Mental workload, task performance, and enjoyment are proposed as the most important variables at the usage layer. Interactions between the layers are described. Examples are given of the model which has been used in actual service design work. Finally, it is suggested that the model could also be used for dynamic adaptations.