Interactive multimedia sessions have uncertain, varying consumption rates due to users' interactive behavior. In this paper, we propose two approaches for prediction of consumption rates required for admission control. They differ in the assumptions of the available knowledge: The observation-based approach predicts the future consumption from the past system behavior. The stochastical approach requires a user behavior model from which the prediction is deduced. We discuss the pros and cons of the two approaches with respect to available information sources, accuracy of prediction, and suitable scenarios.