Based On The Application Layer Of The Small Multi-party Video Communication, Multicast Technology

In recent years, due to the rapid development of network technology and the popularization of internet, our lives have changed quite a lot. Various network applications have greatly enriched the method of information exchange and communication. However, such affluent applications bring great challenges to the capability of network, especially the internet.Among these applications, multimedia communication is almost the hottest research area. Due to the serious requirements of real-time transmission and continuity, it asks for more bandwidth and less latency of the network to ensure the QoS (Quality Of Service). Besides, unicast transmission can't afford excellent service when multiparty communication is combined. The only way to resolve this is to adopt multicast to achieve best bandwidth usage and latency requirements. There are two popular methods to do it: IP Multicast which needs support of routers and Application-Level Multicast (ALM) which needn't such support. The conventional wisdom has been that IP is the natural protocol layer for implementing multicast related functionality. However, more than a decade after its initial proposal, IP Multicast is still plagued with concerns pertaining to scalability, network management, deployment and support for higher layer functionality such as error, flow and congestion control. So ALM is explored as an alternative architecture for Multicast functionalities, especially in the internet environment.The main difference between ALM and IP Multicast is that where to execute the rout selecting is different. In the former, the rout selecting is placed on application layer and IP layer in the latter. Due to this transferring, ALM needs no support of hardware and software in IP layer and this greatly enlarged the application range. Up till now, all the research work about ALM indicate that ALM is more efficient than simple unicast although less efficient than IP multicast.In this paper, we propose a novel Application-Level Multicast protocol which targets on the small-scale multiparty videoconferencing. The system aims at equally allocating bandwidth among all the links while ensure the latency requirements rather than just reducing transmission delay. Through this way, the system proportions the risk of one route congestion to all the ones and then tends to be more stable and can tolerate more network fluctuation. Besides, the system also adopts the centralizedmodel which introduces a central point to collect the network status information and compute the routes. It can be easily seen that the computed routes would be optimized totally and the convergence of routes update would be more rapid. Furthermore, in order to reduce the jitter impact when routes updated, routing information are put into every packet rather than saving them in each node. So, every packet becomes self-routed without the need of coordination between nodes. Experimental results indicate that the proposed ALM protocol is more efficient than the simple unicast, and more suitable for the small-scale multiparty videoconferencing than other ALM systems.