Co-evolution of content popularity and delivery in mobile P2P networks

Mobile P2P technology provides a scalable approach for content delivery to a large number of users on their mobile devices. In this work, we study the dissemination of a single item of content (e. g., an item of news, a song or a video clip) among a population of mobile nodes. Each node in the population is either a destination (interested in the content) or a potential relay (not yet interested in the content). There is an interest evolution process by which nodes not yet interested in the content (i.e., relays) can become interested (i.e., become destinations) on learning about the popularity of the content (i.e., the number of already interested nodes). In our work, the interest in the content evolves under the linear threshold model. The content is copied between nodes when they make random contact. For this we employ a controlled epidemic spread model. We model the joint evolution of the copying process and the interest evolution process, and derive joint fluid limit ordinary differential equations. We then study the selection of parameters under the content provider's control, for the optimization of various objective functions that aim at maximizing content popularity and efficient content delivery.

Modelling and analysis of new coolstreaming for P2P IPTV

Peer to peer networks are being used extensively nowadays for file sharing, video on demand and live streaming. For IPTV, delay deadlines are more stringent compared to file sharing. Coolstreaming was the first P2P IPTV system. In this paper, we model New Coolstreaming (newer version of Coolstreaming) via a queueing network. We use two time scale decomposition of Markov chains to compute the stationary distribution of number of peers and the expected number of substreams in the overlay which are not being received at the required rate due to parent overloading. We also characterize the end-to-end delay encountered by a video packet received by a user and originated at the server. Three factors contribute towards the delay. The first factor is the mean shortest path length between any two overlay peers in terms of overlay hops of the partnership graph which is shown to be O (log n) where n is the number of peers in the overlay. The second factor is the mean number of routers between any two overlay neighbours which is seen to be at most O (log N-I) where N-I is the number of routers in the internet. Third factor is the mean delay at a router in the internet. We provide an approximation of this mean delay E W]. Thus, the mean end to end delay in New Coolstreaming is shown to be upper bounded by O (log E N]) (log N-I) E (W)] where E N] is the mean number of peers at a channel.

Análise de desempenho de redes p2p com protocolo push/pull para distribuição de vídeo na presença de nós não-cooperativos.

O uso de Internet para a distribuição de fluxos de vídeo tem se mostrado uma tendência atual e traz consigo grandes desafios. O alicerce sobre qual a Internet está fundamentada, comutação por pacotes e arquitetura cliente-servidor, não proporciona as melhores condições para este tipo de serviço. A arquitetura P2P (peer-to-peer) vem sendo considerada como infraestrutura para a distribuição de fluxos de vídeo na Internet. A idéia básica da distribuição de vídeo com o suporte de P2P é a de que os vários nós integrantes da rede sobreposta distribuem e encaminham pedaços de vídeo de forma cooperativa, dividindo as tarefas, e colocando à disposição da rede seus recursos locais. Dentro deste contexto, é importante investigar o que ocorre com a qualidade do serviço de distribuição de vídeo quando a infraestrutura provida pelas redes P2P é contaminada por nós que não estejam dispostos a cooperar, já que a base desta arquitetura é a cooperação. Neste trabalho, inicialmente é feito um estudo para verificar o quanto a presença de nós não-cooperativos pode afetar a qualidade da aplicação de distribuição de fluxo de vídeo em uma rede P2P. Com base nos resultados obtidos, é proposto um mecanismo de incentivo à cooperação para que seja garantida uma boa qualidade de vídeo aos nós cooperativos e alguma punição aos nós não-cooperativos. Os testes e avaliações foram realizados utilizando-se o simulador PeerSim.

P2P信任模型中的共谋团体识别技术研究

随着P2P网络的迅猛发展，P2P网络的安全性问题受到越来越多的关注。由于P2P网络先天的开放性、匿名性等特点，信任问题已经成为制约P2P网络发展的瓶颈。信任模型的出现为P2P网络提供了一套有效的安全机制，理论和实践证明P2P信任模型在提高P2P网络安全性和健壮性方面效果显著。但是，P2P信任模型自身的安全性成为另一个需要关注的问题，尤其是共谋团体攻击对P2P信任模型造成的安全威胁最为严重。如何有效抵制共谋团体的攻击、提高P2P网络的安全性成为当前亟需解决的问题。本文针对P2P信任模型中的共谋团体问题进行研究，取得了一系列成果： (1) 针对P2P信任模型中节点的评价行为提出了基于节点行为向量的共谋团体识别方法。通过对节点之间的行为相似度进行聚类分析，可以有效识别网络中存在的共谋团体，在提高信任模型安全性方面具有明显效果。 (2) 基于节点行为的复杂性和模糊性，提出了基于模糊逻辑的共谋团体识别方法。该方法扩展了对节点行为的描述范围，并利用模糊逻辑分析节点行为的相似度，充分考虑了节点评价的模糊特性，更加有利于对共谋团体的识别。 (3) 受恶意代码检测技术的启发，提出基于行为轮廓的共谋团体检测方法。通过构建节点和节点集合的行为轮廓，对节点和节点集合的行为进行了更加全面深入的描述，在此基础上通过分析行为轮廓相似度识别共谋团体。同时，通过引入集合行为轮廓的概念，降低了传统聚类过程中的计算开销，使节点之间的共谋行为更加容易识别。 总的来说，本文针对P2P信任模型中的共谋团体，通过分析共谋团体的行为特征，提出了一系列基于行为相似的共谋团体识别方法，适应当前现实网络环境的需要，可以有效地识别网络中存在的共谋团体，大大提高了P2P信任模型对共谋团体攻击的抵制能力。

基于P2P的僵尸网络及其防御

僵尸网络作为网络犯罪活动的平台,正朝着P2P等分布式结构发展.研究僵尸网络的发展方向以及构建技术,有助于我们全面地了解僵尸网络活动的特点,从而更好地开展僵尸网络的检测和防范研究.本文分析了攻击者的需求,提出了一种基于层次化P2P网络技术的新型僵尸网络结构,并对这种僵尸网络的可行性和具体的传播、通讯、控制等各个方面进行了深入分析和探讨.在此基础上,我们通过模拟实验对各种防御策略的有效性进行了分析和评估,实验数据表明,在考虑实际可操作性条件下,现有的防御策略难以有效摧毁P2P结构僵尸网络.最后,我们讨论了这种新型僵尸网络可能的防御方法.

P2P信任模型中基于行为相似度的共谋团体识别模型

提出了一种P2P环境下的基于节点行为相似度的共谋团体识别模型CCD(colludingcliquedetector),并给出了该模型的数学描述和分布式实现方法。该模型可以通过分析节点之间的行为相似度有效地检测出信任模型中存在的共谋团体,从而帮助信任模型排除共谋团体的干扰。仿真实验表明,CCD模型在共谋团体的检测和抵制方面效果显著,使信任模型在面对共谋攻击时的健壮性和下载成功率都大大提高。

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(identifierrangebasedrouting,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.

非结构化P2P系统Overlay优化技术综述

非结构化P2P Overlay网络的结构松散,网络中资源的分布没有明确的限制,这使得非结构化P2P Overlay网络中的资源搜索在很大程度上依赖于通信开销巨大的泛洪法,因而非结构化P2P系统在伸缩性,可用性等方面,存在明显的不足.非结构化P2P Overlay网络的上述特点决定了非结构化P2P Overlay优化技术的重要性.本文分四大类别,对非结构化P2P Overlay优化技术进行了介绍,分析比较了各类方法的优劣以及它们的适用场合,并在此基础上对未来工作进行了展望.

移动自组网中感知拓扑失配的P2P覆盖网构建

对等计算主要关注构造在应用层的虚拟覆盖网络.在上层的覆盖网络和底层的物理网络之间,通常都存在着拓扑失配.这种失配会导致P2P应用耗费相当大的通信开销.在移动自组网中,由于资源(比如带宽,电池能量等)和节点移动性的限制,拓扑失配问题变得更加严重.而已有工作对这一问题没有进行充分的研究.本文研究了移动自组网中的拓扑失配问题对非结构化P2P覆盖网中目标搜索的影响,并提出一个分布式的、能感知拓扑失配的覆盖网络构建算法D-TAOC.分析和实验表明在D-TAOC构建的拓扑失配感知的覆盖网中,P2P应用能够在较少牺牲目标搜索效率的前提下,明显地降低网络中的通信负载.

P2P平台的关键技术

随着Internet的快速发展，P2P系统在研究领域和产品开发中备受关注。鉴于P2P系统的应用背景差异较大，我们将其划分为P2P平台层和P2P应用层。本文主要讨论P2P平台的关键技术，着重分析了定位、通信、安全、性能等方面的技术，为我们设计和实现P2P应用提供借鉴。

P2P系统服务质量研究

随着P2P计算受到越来越多的关注,如何系统全面地对一个P2P系统作出评估成了一个非常重要的问题.本文从服务质量的角度来系统地考虑P2P系统评估的问题,提出了一个P2P系统服务质量度量框架,以帮助和指导P2P系统的设计和选择.