Continuous media communication requires timely delivery of data such as digital video and audio packets. Quality of Service (QOS) parameters specify the temporal and spatial characteristic of such continuous media data. To insure timely delivery of continuous media data, the system needs to minimize the communication delay by securing required processor and network resources. We have extended the Capacity-Based Session Reservation Protocol (CBSRP), which was proposed for realizing predictable real-time communications, to support dynamic control of QOS. We have implemented a QOS control scheme by which the network dynamically adjusts the allocation of net-work bandwidth on a Fiber Distributed Data Interface (FDDI) network. In this paper, we describe the definition of our QOS model, the extension of CBSRP to support dynamic control of QOS, and the implementation and evaluation of extended CBSRP in our distributed systems testbed. Advanced Real-time System (ARTS).