【作者】 庄宏；

【导师】 许胤龙；

【作者基本信息】 中国科学技术大学 ， 计算机软件与理论， 2010， 博士

【摘要】 近年来随着P2P技术的不断发展,P2P软件尤其是P2P视频点播用户数量不断增加,而计算机网络及硬件系统发展相对迟缓。技术发展的不平衡导致P2P应用和因特网服务供应商(ISPs)之间产生了很多问题：一方面,P2P应用尤其是P2P视频点播应用占用了大量因特网带宽,给ISPs带来了沉重的流量负载;另一方面,ISPs针对P2P传输负载的管理方法,也影响了P2P系统的设计和性能,使得P2P视频点播等应用需要做到面向ISP友好。研究表明：两者进行协作将有助于网络传输性能的改善。而ISPs辅助方法是当前ISPs和P2P应用协作的重要方法之一,该方法通过ISPs在P2P节点选择中的辅助作用,帮助P2P应用选择那些符合特定优化目标的节点,从而优化P2P应用及ISPs的系统性能。本文主要研究在大规模P2P视频点播系统中,基于ISPs和P2P应用协作,引入ISPs辅助方法,在保证视频应用需求的前提下,降低P2P流带给ISPs的传输负载,并缩短P2P应用的平均邻居节点距离。本文首先介绍了与P2P视频点播系统相关的技术背景知识,说明了在视频点播服务中引入P2P流媒体技术的必要性；然后分析了P2P和ISPs的传输行为的相互影响,说明P2P网络技术给ISPs带来的诸多问题,并且尝试通过P2P协议改进的方法使P2P应用面向ISP友好；之后探讨了当前ISPs和P2P应用协作的主要方法,提出了本文的主要技术路线,对ISPs辅助的节点选择算法进行了改进；最后在引入ISPs辅助方法的基础上进行P2P视频点播系统设计、用户行为建模和资源策略制定,并且完成了原型系统和实验分析。本文的主要创新有以下三点：首先提出了基于IP标识节点的节点选择优化方法,通过IP信息获取部分底层区域信息,在应用层进行路由区域逼近,由自身协议修改的途径使P2P网络面向ISPs友好；其次针对路由动态变化和链路性质差别对ISPs辅助方法的节点选择算法进行了改进,使得算法能够辅助P2P应用选择那些动态路由代价较小和链路代价较小的对等节点,由协作优化的途径改善ISPs的传输性能；第三是在针对产生大规模数据流的P2P视频点播应用,在服务器端身兼CPs和ISPs两职的系统设计中,引入ISPs辅助方法,使得P2P网络在承载主要数据传输任务的同时,获得服务器端的节点选择帮助,尽可能的减少跨区域P2P流。分别由单机、局域网模拟、原型系统实验得到的结果均表明,ISPs辅助方法可以有效降低包括P2P视频点播在内的应用带给ISPs的网络流量负载,并且提高P2P的节点服务质量。更多还原

【Abstract】 In recent years, with the continuous development of P2P techniques, the number of users of P2P especially P2P VOD continuously grows. But the development of Internet services and hardware systems is relatively slow, and then many problems between the P2P applications and Internet Service Providers (ISPs) have been caused. In one hand, P2P applications especially P2P VOD takes much bandwidth of Internet, and brings ISPs much traffic load. In the other hand, the scheduling and routing strategies of ISPs also affect the performance of P2P systems, so that P2P VOD and other P2P systems should make themselves more ISP-friendly. The researches show that the collaboration of ISPs and P2P can improve the performance of transmissions through network. ISP-aided is one of the most important methods in the research of the collaboration of P2P applications and ISPs at this moment. It helps the P2P applications find those peers which match the optimization goals well with the assistance of ISPs, for the purpose of optimizing the performance of both P2P applications and ISPs.This dissertation mainly focuses on reducing the costs of bandwidth and traffic brought to ISPs by P2P in the massive P2P VOD systems, based on the collaboration of P2P applications and ISPs, by introducing the ISP-aided method and analysis of the distributed VOD systems. Firstly, we introduce different kinds of techniques related to P2P VOD, and explain the necessity of introducing P2P streaming techniques to VOD systems. Secondly, we analyze the transmission behaviors of ISPs and P2P applications, describe the problems to ISPs caused by P2P, and try to make P2P applications more ISP-friendly by mending the P2P protocols. Thirdly, we discuss about the main means of collaboration of ISPs and P2P applications in recent research and development, propose some technical methods to improve the peer selection mechanism of ISP-aided method. At last, we design a real P2P VOD prototype introducing ISP-aided based on modeling the behaviors of customers and setting down the resource strategy, complete the experiment and relevant analysis.The main contributions of this dissertation are as followings. At first, we propose an optimize method of peer selection based on the IP-mark-peer. In this way, peers can fetch partial information of underlay topology, set up connections according to LOC (Lines of Communication), and make themselves more ISP-friendly by own modification of the P2P protocol. Secondly, we improve the selection mechanism of ISP-aided targeting the dynamic changes of routing and differences of links. As a result, by the assistance of the modified algorithms, the peers should choose peers with lower costs of dynamic routing and connect to them as neighbors. It is a cooperative way to improve the performance of system transmissions. Thirdly, in the design of P2P VOD system whose servers take the roles of both CPs(Content Providers) and ISPs, we introduce the ISP-aided method, found the assistance mechanism of peer selection in the side of servers, for the purpose of reducing the traffic caused by the P2P transmissions passing through different topology areas keeping the P2P functions. The results of experiment in PC, LAN and a real system show that the ISP-aided method could reduce the traffic loads of ISPs which are caused by P2P applications including P2P VOD and promote the QoS (Quality of Service) of peers.更多还原