Research And Implementation Of Load Balancing And Cache Replacement In P2P VoD Systems

With the rapid development of the Internet and the upgrading of broadband,streaming media ondemand services have become more and more popular among both video sites and social networks.For the bandwidth promotion for traditional service mode of Client/Server(C/S),the cost for service providers and network operators is large and unacceptable.Although Content Delivery Network service reduces backbone network traffic to a certain extent,its maintenance cost and expansibility are also limited.Peer-to-Peer(P2P)network with flexible scalability can make full use of the resource of each node to reduce server load.However,there still exists some issues in P2 P streaming media for the practical applications,such as unstable service,low utilization rate of video and high server load.This thesis focuses on the two key strategies of load balance and cache replacement in P2 P Video on Demand(VoD)system.The specific works are describedas follows:i)The architecture of the P2P-VoD system is designed based on the hybrid P2 P network model and the key technologies of P2 P streaming media.ii)The request queue-based node load balancing strategy is designed.Firstly,the priority of the request is defined by considering the urgency of each request,the scarcity of the request,and the smooth playback threshold.In other words,the priority of the request in request queue is updated when a new request is added to the request queue.Then,the requests are reordered according to the priority in the queue.The processing time is estimated for the reordered request,and the requests that cannot be handled with immediately will be transferred to other nodes.Finally,the node utilization function is designed to select the appropriate target node for the transfer request.Simulation experiments show that the proposed strategy can effectively solve the problem of node load imbalance in the P2P-VoD system.iii)The elimination index-based cache replacement strategy is designed.By studying the existing cache replacement strategies and considering the statistical analysis of the P2P-VoD system logs in the existing researches,the elimination index(EI)is selected as the criterion to adjust system cache.To prevent over-adjustment,combined with the feedback mechanism,this thesis further proposes a new elimination index-based feedback mechanism.After that,in order to select the video block with the lowest cache value,the segment value of video blocks is defined.Finally,the elimination indexbased cache replacement strategis completely designed.Experimental results show that the proposed cache replacemen can effectively reduce the redundant copies of the popular videos,and appropriately increase the number of copies of unpopular videos to reduce server pressure,so as to improve the utilization of the node cache.iv)A P2 P VoD system is implemented.It adopts the proposed load balance strategy and cache replacement strategy.Specifically,this thesis gives the technical framework of the system,and describes the detailed design process of the system network elements through hierarchical structure,static class diagram and data structure.