Research On QoS Oriented Real-time Streaming Transmission Mechanism

With the development of the Internet and computer technology, the real-time streaming applications have been used by more and more people. But with increasing users and the mass real-time streaming data, the existing IP network and real-time streaming transmission technology can not satisfy the QoS requirements of the users. With peer-to-peer technology, the mode of real-time streaming transmission has changed, the QoS issues of real-time streaming transmission have been solved to some certain. But how to construct highly reliable, scalable, large-scale, flow QoS satisfied real-time streaming system in a dynamic peer-to-peer network environment is need to address, and the problem is studied by researchers in recent years.After studying the latest technology of the real-time streaming system comprehensively, the paper analyses the requirement of the real-time streaming transmission QoS, and has a deeply study on the real-time streaming transmission architecture and technology to guarantee the needed QoS, and has achieved some results, the paper's main contributions are as follows:(1) To the requirements of the of real-time streaming transmission on the stability and scalability, a Hierarchical overlay networks based on P2P technology combined with SIP protocol(PSON) is constructed. PSON overlay network has solved the problem of compatibility with the existing real time streaming session application by using SIP protocol to encapsulate the messages. Negotiating about the form of the media with the extensible part of SIP message can solved the heterogeneity problem of participants. The PSON is hierarchical, and the nodes are classified on the different capability, and the stable nodes with high capability maintain the overlay. The result is that the stability of overlay network is. greatly increased, and can meet with the requirement of real-time stream transmission.(2) To solve QoS problem of the real-time streaming "push" mechanism, the paper puts forward an application layer multicast tree construction algorithm base on PSON. The algorithm balances the several key factors of delay, bandwidth and packet loss rate, and the constructed application layer multicast tree can satisfy the users with bandwidth, and reduce the transmission delay to a minimum. During the course of constructing the application layer multicast tree, the algorithm makes full use of the stability characteristics of super nodes in the hierarchical PSON structure and sets redundant nodes to increase the stability of the multicast tree, and decreases the transmission jitter delay. The MDC coding and FEC technology are used to satisfy the different demand from different user, and a real-time streaming transmission algorithm is designed.(3) After analyzing the QoS requirements of real-time streaming "pull" mechanism, a real-time streaming "pull" mechanism based on PSON is designed. In order to meet the different bandwidth and network delay requirements during the course of downloading real-time streaming files, a peer selection algorithm is designed. To solve the caching delay of the real-time streaming downloading, a pieces assignment algorithm is used to allocate the bandwidth among the nodes with the needed resource. In order to improve real-time streaming transmission quality, the paper designs a real-time streaming monitor mechanism to address the problems of the packet loss and reliability.(4) In order to reduce response time for a request node searching for a real-time streaming file in the "pull" mechanism, and the real-time streaming file blocks can be distributed in the overlay network as much as possible to satisfy the requirement of the request users, based on the studying of existing cache technology, real-time streaming file copy and file blocks cache mechanism are designed. This paper studies the threshold for caching a copy and brings forward the method to manage the cached copies; to the distribution characteristics of the real-time streaming file blocks, a block caching algorithm is designed, and the block cache management methods is also be designed.(5) In order to increase the real-time streaming content in the downloading system, to solve the problem of selfishness and common tragedy, the paper designs a bandwidth allocation algorithm based on capacity an incentive mechanism. The contribution values and utility values are designed, and after proving the rule in the bandwidth allocation, the bandwidth allocation algorithm based on the user contribution is put forward. The allocation algorithm provides different service for users with different contribution, and avoids the free-riding and common tragedy problems.