Research On Proxy-Caching Scheduler Based On P2P Cooperation

With the rapid development of computer hardware and Wide Band,multimedia service become more and more popular. As streaming-media technology provide conditions to real-time video and VOD(video on demand),many experts are focused on it. Network structure and scheduler algorithms are research point,for they can affect the efficient of streaming-media system's QoS(Quality of service).In the network structure of streaming-media,the traditional C/S mode is relatively simple and managed easily,however,the capacity of system is impacted seriously by center media server and backbone network and do not adapt to streaming-media service with heavy data and long time. To change this condition,P2P network mode was raised,peers are both server and client for each other. That makes data shared among them,however peers managed difficultly。The regularly accessed data is cached in the proxy server which is relative close to client. Proxy server serves directly to client. Organizing a number of servers as a cluster to increase cache space is an efficient way to reduce the service delay and increase QoS。As the limit of cache space, proxy servers have to cache the most valuable data. It is the import problem of caching algorithm that choosing the most valuable data exactly and assigning to different proxy servers make the system serve more clients and provide better QoS.For resolving above problems of network mode, this paper uses the hybrid network mode with center media server and proxy servers which connect each other by P2P cooperation. This can avoid the condition that system depends on center media server excessively in C/S mode and the condition that peers are managed difficultly in pure P2P network mode.When choosing of data, this paper introduces the media file popularity and caching efficiency based on data statistics. According to the principle that more popular data are assigned more cache, allocate corresponding cache to every media file's prefix by its popularity. When sending the data on networks, the backbone has to send some necessary data to increase alternation with clients and avoid network jitter and guarantee the QoS. Without influence Qos,the system should send data using the edge network to reduce the pressure of backbone. This paper gives the backbone and edge networks different rights, introduces C(i,j,p_j~i)denoting the transmission cost when media file i has p_j~i data on the proxy server j. Prefix sequence and proxy sequence are sorted in ascending and descending order respectively by transmission cost. And then assigning prefix to proxy servers makes the transmission cost as least as possible.The paper proposes Proxy-Caching Scheduler based on P2P Cooperation (PCSPC), which chooses an appropriate networks mode and considers both caching efficiency and transmission cost. This algorithm increases hit ratio, especially in the condition that cache is limited using the way that proxy servers cache the most valuable prefix. It makes data to be sent on edge networks instead of backbone for ensuring the transmission of control information and urgency information on backbone. Especially when lots of client request, the pressure of backbone will increase slowly, this let system serve more clients. In the last section of the paper, simulation results show the effectiveness of the strategy.