Modeling user behavior: a layered approach

The simulation of computer systems requires representative, reliable workload models. When simulating computer systems or components that are influenced by user behavior, this very behavior has to be modeled by using mathematical means. In this article, we propose a user behavior model framework that is constructed in a top-down manner consisting of various layers. The layers offer services to the next higher layer and require services from the layers below. The framework is meant to enable the modeler to plug in his own models at the layers of his choice, thus choosing the right balance between the simulation complexity and creating representative results. We give a description of the layered framework and the corresponding methodology. The approach is then demonstrated on modeling HTTP traffic, to be used in network traffic simulation.