The implementation of bounded-delay services over integrated services networks relies admission control mechanisms that in turn use end-to-end delay computation algorithms. For guaranteed-rate scheduling algorithms, such as fair queueing, delay computation based on Cruz' service curve model performs very well. Many currently deployed networks, be they packet-switched or ATM based, rely on non-guaranteed-rate disciplines, most prominently FIFO and static-priority disciplines. We show that for this class of disciplines the service curve model performs poorly. We propose the Integrated Approach as alternative to the service curve model to cluster servers for delay computaton purposes, and show in a series of evaluations that this new approach outperforms approaches based on the service curve model as well as other currently used approaches.