Reaseach Of Small Group Application Layer Multicast And The Applicaton In Videoconference

Application layer multicast achieve multicast in form of multiple unicast in application layer, it bypass the restrictions of the network layer by such way, but the cost is the consumption of network bandwidth resources and the software system resources. Therefore, large-scale application-layer multicast can only achieve one-to-many applications of single-source; and multi-source application-layer multicast algorithm in general for small-scale applications, such as small-scale desktop video conferencing class. Existing small-scale application-layer multicast algorithm for priority use of the grid, multi-source strategy of tree cover, the algorithm is very complex and difficult to achieve, too much administrative overhead; some tree priority of the centralized algorithm and the existence of the program the function of the hub through a high integration of the network status changes taken to optimize the multicast tree, such as the shortcomings of the strategy is not flexible enough. And how the limited bandwidth conditions, the better to meet the multi-source multi-media applications require real-time, stability has become the small-scale application-layer multicast algorithm of the main issues that need to be resolved.In this paper, the application layer multicast technology progress, the existing small-scale application-layer multicast algorithms are classified and detailed analysis and assessment of the advantages and disadvantages of various algorithms is located. Followed by a desktop video conferencing systems for small-scale application-layer multicast algorithm for small-scale group communication needs and the characteristics of a centralized group management strategies in the strategy, the focal points responsible for collecting and records of members of the node status information, as well as institutions to share information multicast tree; multicast tree node group in the accession process to use this information to select the most suitable parent node; At the same time or in abnormal disconnect from the node, the multicast tree approach to pre-Reconstruction. Finally, based on the above algorithm, is designed and implemented a desktop video conferencing system, which has the deployment of simple, low hardware requirements, the stability of signal transmission characteristics. The system is based on Windows platform, using VC + + development tools in the framework of the preparation of the realization of DirectShow, the system of control signals and multimedia data using a different protocol to transmit at the same time using keying technology, and multimedia data compression technology to ensure that the media data transmission fluid and respond to real-time. In this paper, given the realization of specific methods, and to evaluate the effect of the application.