Research On P2P Streaming Delivery Techniques In Content Delivery Networks

Coming from laboratory of MIT in 1998,Content Delivery Networks(CDN) has become one of the most important techniques in Internet.Delivering content to the users from the nearest servers at the edge of the networks,CDN improves the quality of experience of users,while alleviating the load pressure on backbones and source servers. It gains attentions from a wide range of both academe and industry.Morgan Stanley has predicted an average yearly growth of 31%in CDN market for 10 years.In the support from projects of National Nature Science Foundation of China(NSFC):"Theory Research on Secure Transmission of Application-Supported Video Multicast(No.60473086)" and "Theory Research on the Secure and High-Performance Streaming System based on the P2P Technology(No.60673184)",and from project of National High Technology Research and Development Program of China:"P2P-based Secure Live Streaming System (No.2007AA01Z400)",this dissertation combines the advantages of P2P and CDN to construct a new generation of peer-assisted CDN.By the novel design of architecture,it solves the problem in current CDN of achieving both the scalability and QoS for live streaming services.The merits lie in both academic researches and market perspectives.Application requirements have always been the motivation of the development of CDN.The major challenge to CDN nowadays is how to provide QoS guaranteed and economical content delivery on a large scale,when the content to delivery include massive usage of multimedia applications such as high resolution video web-casting.P2P is a revolutionary theory and technique for research in data delivery on large scales,and a lot of breakthroughs have been made in the area.Therefore,thorough understandings of characteristics of streaming protocols and advantages of P2P techniques will provide new ideas to the solution,and theoretical proof for the feasibility and validity of the solution.First of all,characteristics of streams and current dominate streaming protocols are introduced in detail.Further researches and discussions on delivery of streams in both conventional client/server paradigm and P2P environment are also made.Thus features of the problem objects and new techniques are affirmed.After a massive and thorough survey and analysis of CDN,the development of CDN is characterized into three stages:Cache-assisted,Fiber-assisted,and Peer-assisted,based on the changes of CDN architectures.Researches and productions of each stage are introduced separately.The staging evolutionary theory provides a new point of view to the development of CDN,and the direction for the solution of new architecture.Internet is the working environment of CDN,and the performance of Internet decides whether CDN could meet the demands of live streaming service by both the content providers and the consumers.After the survey,measurements and analysis of the current backbone and access networks of China,the key factors which affect live streaming services in CDN the most is discovered.Therefore the major problems to be solved in order to design and deploy a P2P solution for stream delivery are confirmed.The major part of the contribution is the presented new hierarchical peer-assisted CDN architecture for live streaming services,based on the previous fundamental researches.The new design introduces P2P overlay in two separate levels of backbone and access networks.By the key elements of overlay routing on datacenter and P2P streaming in localized client regions,the CDN and P2P are combined to solve the problems.Results of tests in practicing applications have proved the value of the new architecture,which proves scalability while maintaining QoS of experience.For the techniques which affect performances of P2P applications,the basic service of peer discovery is further improved.After the analysis and comparison of several basic peer discovery methods,a new hybrid mechanism of peer discovery is presented.The new solution improves the efficiency of peer discovery while providing certain level of robustness,which is valuable for elevating the performance of P2P-related systems such as the presented new hierarchical peer-assisted CDN architecture.In the last section,main research conclusions in this dissertation are given out.The some new directions and problems in the new architecture are given out and analyzed.