MEDIA SCALING APPLIED TO MULTICAST COMMUNICATIONS

Distributed and vertically integrated multimedia environments need tra nsmission control methods based on real-time communication protocols t hat provide a relative quality of service (QoS) in order to support th e many different receiving capacities of group members and their reque sted services. These methods should also provide a dynamic QoS to cope with the temporary CPU overloads and network congestion. Therefore, t his study proposes a cooperative control method for end-to-end QoS con trol at transport layers and point-to-point control at network layers. The former method is mainly a set of flow-monitoring and flow-adjusti ng functions, while the latter isa set of flow-control functions. In a ddition, QoS presentation functions including QoS level scheduling at application layers and establishment of QoS connections over ATM at da ta link layers are necessary to make the best use of the middle layers ' QoS controls. As a result, real-time transport services on multimedi a systems can be achieved with vertically integrated QoS controls at e ach layer. These controls are implemented on widely-used internet prot ocols (IP) and then evaluated on practically used systems and wide-are a networks. Experiments over experimental ATM-LAN environment at NTT I nformation and Communication Systems Laboratories and the ATM-WAN of t he Keio University information super-highway show that MPC (multicast protocol for continuous services) applied multimedia systems are prefe rable to the conventional approach in terms of packet loss rate and de lay jitter. (C) 1998 Elsevier Science B.V. All rights reserved.