This paper focuses on the operation of the Bandwidth Broker, an entity that is responsible for managing the bandwidth within a network domain and for the communication with Bandwidth Brokers of neighboring domains. A very important aspect of the Bandwidth Broker is its admission control module that determines whether the bandwidth reservation requests are going to be accepted or not. We summarize the status of the current research in this field and propose a novel architecture for the admission control module that aims at achieving a satisfactory balance between maximizing the resource utilization for the network provider and minimizing the overhead of the module. This is achieved by gathering and examining sets of book-ahead requests and by adapting the size of the set to be examined so that the network utilization and the computation overhead are appropriately balanced.