Research And Design Of Multi-Agent Media Service Network

With development of the Internet and prevalence of multimedia,transmission bottleneck has become the main problem in multimedia network applications.In order to solve the transmission bandwidth problem,CDN(Content Delivery Network)and P2P which are proposed recently solved the problems occurred in traditional client/server systems to some degree and are widely applied in various multimedia applications.But either CDN or P2P has its own limitations to provide high quality services,such as geographical restricts,commercial version constraint,and waste of transmission bandwidth,and so on.The research objective of this thesis is to propose a multi-agent multimedia service network(MAMSN)based on the idea of "multi-point service" which integrating both the advantages of CDN and P2P.Aim at the geographical restricts of the generalized star frame-structure in CDN and the bandwidth wasteful problem caused by non-center frame-structure in P2P,a triple cyclic framework is proposed in this paper,combined both star frame-structure and freedom connection.This framework can lessen the occupation of bandwidth as small as possible,while at the same time to ensure the transmission efficiency.The first layer acts as a central controller(non-real-time),while the agents work in the second layer provide transmission service,and the connection mode adopted in the second layer is non-symmetric where the resources deposited in agents are different and nonuniform, and have no correlation among them.These agents construct a virtual storage pool. The third layer consists of client terminals.The connection link between clients and agents are not fixed,and can be adjusted dynamically.The agent layer is one of research focus points in this paper.Because of the non-symmetric allocation among agents,to design the allocation algorithm to distribute the multimedia resources among all these agents is one of the key problems in this research.The basic principle of resource distribution is to deliver multimedia (such as videos)as much as possible and to make enough copies of the multimedia to satisfy the demand of multi-point transmission service.However the visiting frequencies of different multimedia are very different,that means the transmission service requests are very different.In this paper,we do some statistical analysis to some multimedia web services,and based on the basic distribution model of file visiting frequency in the Internet,such as the Zipf distribution and the Pareto principle, a dynamic resource delivery algorithm is designed.Based on the multimedia file's visiting ratio,we can adjust the copies and locations of the multimedia among the agents to improve the transmission service efficiency.Refer to "the order mode in restaurant",multi-point ordering request,simultaneous transmission,and random block storage strategies are adopted in the design of the transmission function of clients in the third layer.Though the load balance is generally taken at the service end in most multimedia application systems today.In this kind of schemes the operation and computation of load balance are complexity,and the computation load at service end is high.We proposed an active load balance policy at the client in this paper,which is served as a complement to the load balance scheme at service end.In order to ensure a reasonable transmission bandwidth at the clients,the over-occupied bandwidths at some clients are restricted to reduce the computation pressure at the service end.