Media scaling applied to multicast communications

Distributed and vertically integrated multimedia environments need transmission control methods based on real-time communication protocols that provide a relative quality of service (QoS) in order to support the many different receiving capacities of group members and their requested services. These methods should also provide a dynamic QoS to cope with the temporary CPU overloads and network congestion. Therefore, this study proposes a cooperative control method for end-to-end QoS control at transport layers and point-to-point control at network layers. The former method is mainly a set of flow-monitoring and flow-adjusting functions, while the latter is a set of flow-control functions. In addition, QoS presentation functions including QoS level scheduling at application layers and establishment of QoS connections over ATM at data link layers are necessary to make the best use of the middle layers' QoS controls. As a result, real-time transport services on multimedia systems can be achieved with vertically integrated QoS controls at each layer. These controls are implemented on widely-used internet protocols (IP) and then evaluated on practically used systems and wide-area networks. Experiments over experimental ATM-LAN environment at NTT Information and Communication Systems Laboratories and the ATM-WAN of the Keio University information super-highway show that MPC (multicast protocol for continuous services) applied multimedia systems are preferable to the conventional approach in terms of packet loss rate and delay jitter.