基于P4P的CDN系统中内容分发节点选择算法

对内容分发网络(CDN)和对等网络(P2P)分别进行了分析对比,指出了它们各自的优缺点,并根据电信运营商主动参与P2P网络(P4P)技术的特点,给出了一种结合P4P、P2P与CDN技术的混合系统的设计方案,以及混合系统中协助CDN节点分发内容节点(伪CDN节点)的选择算法.该算法利用P4P技术获得运营商提供的网络信息,选择合适的边缘节点,贡献出其容量和带宽,为其他节点服务,以减少了系统边缘代理服务器的数量,增大系统容量,同时减少网络骨干网上的负载.模拟实验分析了考虑底层网络情况后,系统在链路花费、时间花费上的改进,结果表明该算法减少了跨网络运营商(ISP)流量,提高了系统性能.     

IPv6中减少ISP交叉流量的结构化P2P流媒体系统

P2P流媒体系统中,减少ISP(Internet Service Provider)交叉流量是一个重要的研究方向,本文提出了一种减少ISP交叉流量的P2P流媒体方案,方案综合考虑了Pull机制、DHT(Distributed Hash Table,分布式哈希表)原理和IPv6地址的聚类特性,从网络拓扑构建和包调度机制两个方面,通过增加ISP内数据共享和减少ISP间数据请求的方式,减少P2P流媒体系统中的ISP交叉流量.仿真结果显示,在大规模系统中,该方案能够有效的减少ISP交叉流量.     

应用网络编码的P2P内容分发

讨论如何在P2P内容分发系统中应用网络编码技术,结论是网络编码能简化P2P内容分发中的Piece Selection算法的复杂度,提高网络资源的利用率.但是,网络编码,必须结合较好的Neighbor Selection和Choking/Unchoking机制,否则,其优势将无从体现.同时,还详细描述在P2P内容分发中如何应用网络编码技术,并逐一讨论应用过程中所涉及到的主要问题.为了证明基于网络编码的P2P内容分发系统的可行性,在单机上实现主要的编、解码算法,分析其时系统资源的消耗.实验的结果是如果一个peer的上栽速率为50 KBps,则编码操作导致的CPU占用率为2.25%,相应的内存开销在20 MB左右.这些数据说明网络编码的系统开销是较轻的,基于网络编码的P2P内容分发系统是完全可行的.     

一种P2P和ISPs协作的P2P节点选择机制

引入ISP跳数(IH)来衡量在自治系统(AS:Autonom ous System)拓扑中位于不同位置的AS跳数的开销,并引入了骨干链接开销(CBC)来衡量P2P应用通过的骨干网络数量.借助于IH和CBC两个参数分析了P2P应用对ISPs流量的影响.并且在此基础上设计一个新的机制,命名为ISP-DDHA.在ISP-DDHA中,针对主要参数设计了相应的路由选择算法,用来改进ISPs和P2P系统性能.实验结果表明:在某些P2P流量负载较大的网络场景中,相比[7],ISP-DDHA可以减少约7.4%的DAH开销、12.1%的IH开销和10.4%的CBC开销.     

安全可控的P2P传输模型的设计与实现

结合PKI、DRM和基于应用层的物理网络拓扑探测技术,提出安全可控的智能节点弹性重叠网络流媒体分发模型,解决系统各节点间的信任问题以及媒体资源的版权认证问题,并改进系统覆盖网络拓扑结构,使之符合底层物理网络拓扑,从而减少底层承载网络的流量,提高系统的传输效率,为Internet用户、内容提供商、网络运营商提供一个安全、可控、可管理、可运营的P2P技术解决方案。     

基于P2P的CDN内容分发机制研究

随着在线直播、在线点播、在线游戏、网络电视等大规模网络应用的蓬勃发展,多样化、海量化信息的内容分发需求给传统内容分发技术带来新的挑战.为了解决因特网内容分发中服务质量与服务范围的问题,系统研究基于P2P(对等网络)技术的CDN内容分发机制,同时融合了P2P与CDN这两种模式,以此来提高了内容分发的整体系统性能.     

基于网络测量的P2P跨域流量优化机制

P2P技术的普及优化了用户的体验,但对带宽的过度消耗也带给网络运营商巨大的压力。据此提出基于网络测量的、业务相关P2P跨域流量优化机制,该机制对底层网络建立模型,通过综合考量底层的网络信息和具体P2P业务的特殊性来优化节点互联。实验结果表明,该处理机制明显减少了跨域流量,优化了P2P用户的体验。     

结合P2P的媒体分发网络的承载量分析

近年来结合P2P的媒体分发网络(MDN)越来越受到人们的关注.它通过将P2P技术引入到传统的内容分发网络,增加了网络的可扩展性,提高了网络的服务质量.为了对这种MDN网络的性能进行分析,本文建立一个线性规划模型,利用该模型可求解出MDN网络的最大吞吐量,进而分析了网络的承载量.通过实验,分析了模型中不同参数和策略配置对网络承载量的影响,从而找出了影响系统性能的各种因素.这些结果对进一步提升网络性能、配置网络参数有很好的指导作用.     

P2P流量识别与监测

随着P2P应用的不断增多,P2P流量所占网络总流量的比重越来越大。准确地识别出网络中P2P应用的流量对网络规划设计、QoS保证等都有十分重要的作用。介绍了当前P2P流量识别的研究现状,综述了四种典型的P2P流量识别技术:端口识别法、应用层特征识别法、流量模式识别法以及连接模式识别,分析了各个技术的优缺点,并对P2P流量识别的发展趋势进行了一些探讨。     

P2P 流量本地优化综合机制

P2P流量的飞速增长,给自治网络（如园区网、校园网）的网络边界带来很大的流量压力。为减少P2P流量对网络关键应用的影响,必须建立P2P流量的本地优化机制,使P2P流量尽可能发生在自治网络内部,缓解网络出口带宽的压力。自治网络的网络边界开始采用基于DPI的P2P流量识别技术,对识别到的P2P流量加以限制。但这种方法只是简单地限制P2P应用,将严重影响用户的流媒体点播体验。提出了一套网络边界P2P缓存机制和本地节点索引机制向结合的P2P流量本地优化策略。     

P2P traffic optimization

Peer-to-peer (P2P) based content distribution systems have emerged as the main form for content distribution on the Internet,which can greatly reduce the distribution cost of content providers and improve the overall system scalability.However,the mismatch between the overlay and underlay networks causes large volume of redundant traffic,which intensifies the tension between P2P content providers and ISPs.Therefore,how to efficiently use network resources to reduce the traffic burden on the ISPs is crucial for the sustainable development of P2P systems.This paper surveys the state-of-art P2P traffic optimization technologies from three perspectives:P2P cache,locality-awareness and data scheduling.Technological details,comparison between these technologies and their applicabilities are presented,followed by a discussion of the issues that remain to be addressed and the direction of future content distribution research.     

Optimally designing caches to reduce P2P traffic

Traffic caused by P2P services dominates a large part of traffic on the Internet and imposes significant loads on the Internet, so reducing P2P traffic within networks is an important issue for ISPs. In particular, a huge amount of traffic is transferred within backbone networks; therefore reducing P2P traffic is important for transit ISPs to improve the efficiency of network resource usage and reduce network capital cost. To reduce P2P traffic, it is effective for ISPs to implement cache devices at some router ports and reduce the hop length of P2P flows by delivering the required content from caches. However, the design problem of cache locations and capacities has not been well investigated, although the effect of caches strongly depends on the cache locations and capacities. We propose an optimum design method of cache capacity and location for minimizing the total amount of P2P traffic based on dynamic programming, assuming that transit ISPs provide caches at transit links to access ISP networks. We apply the proposed design method to 31 actual ISP backbone networks and investigate the main factors determining cache efficiency. We also analyze the property of network structure in which deploying caches are effective in reducing P2P traffic for transit ISPs. We show that transit ISPs can reduce the P2P traffic within their networks by about 50-85% by optimally designing caches at the transit links to the lower networks.     

Characterization of community based-P2P systems and implications for traffic localization

In this paper, we present one of the first and most extensive characterizations of closed community-based P2P systems. Such systems are organic groups of peer-to-peer (P2P) clients, which can be joined only by users belonging to a certain network (e.g., connected to a given Internet Service Provider (ISP)). A number of factors motivate the growth of these communities, such as quality of content, anonymity of transfers, and the potential for better performance that enhances user experience. Our study is conducted in two contrasting environments—a campus network and a national ISP—located in different continents. In both cases, large-scale closed communities have been found to be the predominant P2P systems in use. We shed light both on the factors motivating the growth of such communities, and present results characterizing the extensiveness of their usage, the performance achievable by the systems, and the implications of such communities for network providers. While our findings are interesting in their own right, they also offer important lessons for ongoing research that seeks to localize traffic within ISP boundaries. In particular, our results suggest that (i) in ISPs with heterogeneous access technologies, the performance benefits to users on localizing P2P traffic is largely dependent on the degree of seed-like behavior of peers behind high-bandwidth access technologies; and (ii) while localization can reduce the traffic on Internet peering links, it has the potential to cause a significant increase in traffic on internal links of providers, potentially requiring upgrades of network links.     

P2P技术的发展与应用

P2P是当前互联网上的热点技术之一。P2P技术的本质是化集中处理和存储为分布处理和存储,将闲散的资源集中起来使用,因此它是一种很有创意的技术,一种很好的技术,有着十分广阔的使用前景。文章首先将P2P网络结构与传统的C／S网络结构进行了对比,总结了P2P技术在利用网络中的大量闲置资源,避免服务器带来的瓶颈问题,降低网络成本等方面的优势。然后,对P2P技术的特点以及P2P技术的发展过程作了简要分析。最后,讨论了P2P技术在文件交换、对等计算、协同工作、即时通信和搜索引擎等方面的应用以及面临的挑战。     

Evaluation of a comprehensive P2P video-on-demand streaming system

Video-on-demand (VoD) streaming has recently become a popular service on the Internet, with several companies offering videos to a global audience. However, traditional client/server based VoD streaming systems can be very bandwidth intensive and expensive to maintain, especially for high quality video content. To improve the scalability these systems, the use of peer-to-peer (P2P) networking has been proposed, but despite the efficiency of applications such as BitTorrent for downloading of large files, it is not simple to use P2P techniques for streaming. Problems such as firewalls and freeloaders reduce the efficiency of both types of P2P systems, but for real-time services such as streaming, the result can be reduced playback quality. Other issues include the traffic load imposed on ISPs by P2P networks, which can motivate ISPs to interfere with the P2P traffic. Finally, protecting against malicious modification of content can increase overhead, response times, and startup delays.We consider these issues to be fundamental to the problem of P2P based VoD, but despite the large amount of research that has been done in this field, these issues have largely been ignored. To address this, we present an evaluation of the Streaming P2P Protocol (SPP) architecture. By studying the problem as a whole we have found a simple and comprehensive solution that addresses all the four issues listed above. To show that the system is not only scalable, but also that it can be implemented efficiently, we have used both simulations and experiments on PlanetLab for evaluation. The results show that the combination of cache nodes and use of end-user resources found in the SPP architecture can give a low load on servers and ISPs, even when firewalls are taken into consideration. Furthermore, we observed low startup delays and few playback errors during the PlanetLab experiments. The scalable and low-cost distribution of content possible with the SPP architecture should be suitable for both large-scale commercial distributors and users of community networks with limited resources.     

P2P文件污染与防御

文件污染是P2P文件共享系统面临的主要安全威胁之一。由于没有中心机构监督用户行为及其共享的内容,恶意节点可以通过P2P传播病毒,木马等恶意内容,这些行为严重影响了P2P文件共享的系统性能。本文对P2P文件污染的研究现状进行综述,调查现有P2P系统中存在的文件污染现象及防御方法,分析了目前防御机制面临的问题。     

A research on dynamic allocation of network resources based on P2P traffic planning

With the rapid development of P2P applications, its consumption of bandwidth resources brought increasing pressures to ISPs. How to manage P2P traffic efficiently, both to improve the efficiency of network and to protect the interests of P2P users, is widely concerned by industry and academia. Although some traffic planning scheme to the P2P apps such as P4P can alleviate the pressure on bandwidth resources to some extent, it requires deep cooperation between ISPs and P2P service providers. Therefore it has some limitations to independent DPI strategies. In addition, there is no flow planning strategies which can rapidly response to ISPs’ QOS requirements such as sudden changes of bandwidth reservation and so on. This paper analyses current mainstream P2P optimization strategies, and then put forward a network resources dynamic allocation (NRDA) technology based on the deployment of P2P traffic stand on the ISPs’ position. This technology enables ISPs to have the ability to manage the P2P traffic on the specified links independently and efficiently, especially for the rapid response of unexpected resource requirements. NRDA implements an overall planning of network resources and makes the network flexible, provides the resource planning ability to the ISPs.     

结构化P2P网络上可靠的基于内容路由协议

在结构化P2P网络上构建基于内容的发布/订阅系统,可以很好地支持大规模、高度动态的分布式应用.然而,现有的基于内容的路由协议在P2P网络上只能提供弱的可靠性保证.根据结构化P2P网络的路由协议的特点,设计了一种新型的基于内容的路由协议--基于编码区间的路由(identifier range based routing,简称IRBR)协议.IRBR协议具有良好的容错性,只要事件的发布者与订阅者之间在P2P网络中是可达的,则订阅者一定能够收到它所订阅的事件,且只收到一次.同时,该协议也比现有的协议具有更高的事件路由效率.在Pastry上开发了一个原型系统,模拟实验表明了该协议的效率和容错性.     

基于P2P模式的DRM系统体系和协议研究

在分析了P2P网络模式和数字版权管理(DRM)技术体系的基础上，提出基于P2P模式的DRM系统体系，并对系统体系结构和传输协议进行了研究和探讨。基于体系的拓扑结构，提出了体系功能框架，并对其中内容管理、内容标识、付费机制和质量控制进行分析和设计。同时以数字内容的生命周期和价值链为依据，对体系的工作流程进行了深入的探讨。给出了体系的数字内容上传和下载协议，实现了P2P网络模式与DRM技术体系的有效集成。