Hierarchical Structure Based On Application Layer Multicast Model Design And Implementation

Compared with the difficulty IP multicast has encountered in, ALM (application layer multicast) has great advantage in deployment, security, expansibility, congestion control and other aspect, it has been developed rapidly in recent years. Many ALM model has been proposed, some have been implemented successfully, while some remain in realm of theory. Combination of ALM and CDN will be the development trend of future.This paper first analyzes the current ALM model, and shows their solution in data transmission, topology building, maintenance, utilization, load balancing. On this basis, this paper proposed a new ALM model-AOCast. This is a hierarchical model, it has a logical view in administrator server, which contains the whole topology in administration, and nodes will be filled in corresponding position according to its participating sequence. One has relation with some nodes in above layers. Based on this we can build a data transmission tree. Topology administration and maintenance are done centralized. When new node joined, it must first connect to the administrator server, the server then return some nodes’ information which is selected according to some rules. Node chooses one of them as its data source, the main basis for Selection criteria is upload bandwidth and transmission delay. The node also need prepare to provide data for other node. Data source only provides data to the nodes in the first layer. AOCast use adjustment method in "heap sort" to optimize transmission performance, its main idea is move the node which has good forward capability to the layer closed to the data source, while move worse nodes to the layer far away from the data source. This intent is making full use of the nodes’ capability on forwarding data, minimizing the delay caused by lack of forwarding capability. Through the calculation and result from simulation using peersim, we proved that the AOCast model has excellent behavior in realm of topology. Finally, we use this model to design and implement a traffic information delivery system.