The Differentiated Services architecture targets at providing scalable network Quality of Service by means of aggregate scheduling. However, the defined framework itself only gives a number of building blocks, which do not constitute services yet. In order to provide well defined services, the composition of the respective traffic aggregates has to be controlled. This is usually the task of the admission control. In this paper, we investigate a scenario, where access to advanced network services is provided by a parameter based admission control, which allows to provide hard Quality of Service guarantees. We address the scenario of a Premium service which provides bandwidth on demand and which in addition allows to give deterministic bounds on the delay. According the reservation-based approach of the Integrated Services architecture, we propose a set of admission control procedure that are part of a particular resource manager such as a Bandwidth Broker. In extending the Network Calc...