P2P组播网络容量分析

最近几年来,P2P技术在研究领域受到广泛关注,很多系统开始采用P2P架构进行组网,向用户提供各种服务,如下载服务和组播服务.人们普遍认为P2P系统中节点越多,P2P对等技术的优势也越明显,系统的容量几乎没有限制.但对P2P组播网络,这一结论必须满足一定条件才能成立,本文从基本的流量关系出发,推出P2P组播网络理论上能够容纳的最大节点数量和节点流复制能力的关系,并以构造方式证明了对任何数量的节点,只要总的复制能力超过节点数量,理论上存在一种组播组织方式,实现稳定组播,为P2P组播网络的优化提供了理论指导.     

基于P2P模式的身份验证系统

P2P(Peer-to-Peer)网络是一种新型的不依赖于集中式服务器的分布式网络模型。将P2P技术应用于身份验证服务,使系统在节点间分配来自用户的身份验证请求。首先提出在节点上采用Agent技术进行身份验证和证书管理,并在系统中引入信任机制来优先选择邻居节点和评价信息质量。然后介绍了身份验证系统的结构和用户访问本系统的实例,最后讨论了系统的通信方式。     

基于P2P技术的校园网络课堂教学系统通信模型的研究

在研究P2P技术的基础上,提出了基于P2P技术的校园网络课堂教学系统的通信模型.该模型采用IP层组播和P2P通信建立教师与学生,学生与学生之间的点到点视、音频和文本信息的实时通信交互,发挥了网络节点资源,增强了课堂教学双方交互的实时性,达到现场教学的效果.     

一种媒体直播的P2P自适应网络快速传输模型磁

为解决媒体流在网络直播的低延迟与可扩展性,结合P2P的特点,研究了一种基于P2P的自适应网络快速传输模型。该模型首先对网络节点状态进行分类,通过一种位索引机制实现节点状态的识别,接着在MST 覆盖网络基础上,探讨了一种面向请求节点构建MST的P2P媒体直播系统,并提出了一种自适应网络快速传输控制算法。数学模型分析与模拟结果表明提出的模型能较大程度地缩短端到端传播的延迟时间,且减少跳点数与服务负载,从而进一步提升了媒体播放的流畅性,为采用P2 P技术实现媒体的快速直播提供了很好的参考与借鉴。     

基于P2P的多播控制协议的研究

提出了一个基P2P的多播控制协议。首先总结了大规模流媒体多播传输时采用IP组播技术和CDN技术所存在的不足,之后提出P2P多播所面临的问题,接着阐述了一个基于P2P的多播控制协议中关于节点加入、父节点选择、节点断开以及重连接时如何避免循环等关键技术,最后通过仿真实验对协议进行验证并得出结论。     

P2P全文信息检索系统的路由机制研究

本文介绍了一个基于P2P网络建立的全文信息检索系统的路由机制,在实现系统路由时采用了分层机制,将P2P网络中的节点分成超级节点和普通节点,超级节点间采用非结构化的P2P网络搜索技术,普通节点采用结构化的P2P网络搜索技术,使得整个网络的路由趋于稳定的结构.     

基于P2P的视频会议系统节点选择机制的改进研究

随着P2P技术迅速发展,主要基于P2P技术的视频会议系统作为P2P技术的重要应用之一,且系统的节点选择机制则成为该领域的一个研究热点.利用P2P技术的核心思想构建视频会议系统网络结构,并通过改进系统Chord网络的路由机制来达到改进系统节点选择机制的目的.     

结合IP组播的P2P流媒体直播系统

在流媒体系统中利用P2P技术与IP组播各自的优势,提出了一种结合IP组播的P2P流媒体直播系统,不仅能够充分利用用户节点的资源,减轻流媒体服务器与骨干网的负载,提高系统的可扩展性和可用性,而且有效地提高了P2P流媒体直播系统中视频流的服务质量。     

P2P网中基于IP组播的发现机制研究

对等网络技术是近年来计算机网络技术的一个热点,而对等技术中的一个热点技术就是如何找到节点的发现机制问题。介绍了P2P技术及其发现机制和IP组播的原理,利用IP组播技术来解决P2P中对等体的发现问题。文中分析并建立了一个IP组播发现模型,在此基础上,结合SUN公司为P2P分布式计算提供的通用统一、可互操作的平台JXTA技术,实现了IP组播技术在P2P网络对等点发现机制中的应用,有效地解决了单点发送多点接收、多点发送多点接收的问题。     

基于自适应组播机制的P2P阻塞算法研究

P2P网络中节点利用阻塞机制作为节点选择算法,以确定节点间相互的服务对象.但是在传统的节点阻塞算法中存在着节点连接时间过高,首块资源获得较慢,系统链路利用率不高等问题.提出一种自适应组播机制,利用动态分组的路由方法,充分考虑各节点间的可用带宽,能够很好的解决在传统阻塞算法中存在的首块资源获取过慢,带宽利用不高等问题.     

Modeling and optimization of survivable P2P multicasting

Various solutions based on Peer-to-Peer (P2P) multicasting have been gaining much popularity in recent years, since P2P multicasting can effectively support live streaming of various content. In this work we assume that the P2P multicasting is used to distribute content with high reliability requirements, e.g., weather warnings, security updates, financial data, security warnings, etc. The main idea to provide protection of the system against network failures is to establish several (at least two) disjoint multicasting trees. Our discussion in this paper centers on the problem how additional survivability constraints to provide failure-disjoint trees impact the operation of P2P multicasting systems. As the performance metrics we propose to use: streaming cost, maximum delay and throughput. The possible failure scenario we take into account is a single failure of one of the following network elements: streaming server, overlay link, uploading node and ISP link. We examine the topic of survivable P2P multicasting applying offline optimization methods and simulations. In the former case we formulate Mixed Integer Programming (MIP) models and use the CPLEX solver to obtain optimal results. For the streaming cost objective we compare two MIP formulations in terms of the complexity and execution time. Results show that our formulation provides much better performance compared to the classical P2P multicasting formulation proposed in the literature. Moreover, in the case of the streaming cost problem we propose a new evolutionary algorithm that yields results for larger networks than the CPLEX solver. The simulations are run to emulate a distributed network environment, in which each node makes its own decisions. Results obtained using both research methods confirm that the survivability of P2P multicasting can be achieved with relatively low additional system overhead for all three considered performance metrics: streaming cost, maximum delay and system throughput.     

基于分布式代理的自适应视频会议系统的设计

如何克服服务器负载过重造成的瓶颈效应,及如何适应网络的动态变化,是视频会议系统一直面临的问题.提出了一种基于分布式代理的自适应视频会议系统.该系统充分利用当前的网络条件,采用分布式代理,使用应用层组播和IP层组播相结合的混合组播方式,解决了服务器瓶颈问题;采用基于MPEG-4FGS速率修整技术,使系统具有极好的网络自适应性.     

基于IPv6的P2P组播应用的研究与实现

介绍IPv6组播和P2P多播技术,分析FreePastry的路由算法,重点改进对象EpochInetSocketAddress对源路由节点地址的管理方法,在FedoraCore6系统环境下双栈技术的运用,以及在IPv6环境下设计并实现了基于P2P的组播应用。MTAP6由P2P重叠网和接入网两个部分组成,其中重叠网部分采用基于P2P的应用层组播技术,接入网部分采用基于IPv6的组播技术。最终实现了以视频会议、视频点播、远程教育为特色的新型多媒体组播应用     

P2P流媒体传输Agent的ACE设计与实现

当前的流媒体系统一般是基于C/S模式和IP组播技术,这限制了用户数量且IP组播需先得到ISP支持。P2P技术的引入有效地解决了系统负载问题,但是传统的P2P系统减弱了集中控制能力。提出了一种多A GENT的P2P流媒体传输系统,该系统可以有效保持集中控制能力,介绍了A GENT的ACE(A DAPTIVECOMM UN ICATION ENV IRONM ENT)实现技术。经过测试,该系统具有很强的可靠性和网络集中管理能力,展现出ACE在网络开发上的高效性和灵活性。     

A video conferencing system based on SDN-enabled SVC multicast

Current typical video conferencing connection is bridged by a multipoint control unit (MCU), which may cause large delay and communication bottleneck for the whole system. With the development of network technology, a video conferencing system can be implemented based on software-defined networking (SDN), which makes the service controllable and improves the scalability and flexibility. Additionally, a video encoding method called scalable video coding (SVC) can also help. In this paper, we propose a video conferencing architecture based on SDN-enabled SVC multicasting, which discards the traditional Internet group management protocol (IGMP) and MCU. The system implements SVC multicast streaming to satisfy different device capabilities of various conference terminals. The SDN controller is responsible for dynamically managing and controlling the layers of a video stream when a conference member faces network congestion. Also, a conference manager is designed to facilitate the management of the conference members. Experimental results show that our system can not only provide a flexible and controllable video delivery, but also reduce the network usage while guaranteeing the quality of service (QoS) of video conferencing.     

HEURISTIC ALGORITHMS FOR SURVIVABLE P2P MULTICASTING

The growing volume of Internet traffic, increasing popularity of streaming services, and limited scalability of existing network techniques trigger the need to develop new delivery solutions based on a multicasting approach. Multicasting—defined as a one-to-many delivery technique—enables effective distribution of many kinds of content to end users. In this article we focus on peer-to-peer (P2P) multicasting, which combines concepts of P2P systems and multicasting solutions; in other words, the multicast tree is constructed using end hosts (peers). Because P2P multicasting can be applied to deliver content with high reliability requirements, we introduce to P2P multicasting additional survivability constraints that guarantee delivery of content in the case of network failures. We formulate a mixed-integer programming (MIP) optimization problem of survivable P2P multicasting. Because the problem is nondeterministic polynomial time (NP)-hard and exact methods such as branch-and-cut can be applied for only a relatively small problem instance, we propose two heuristic algorithms based on evolutionary approach and Tabu Search methods. Extensive computational experiments show that both heuristic algorithms provide results close to optimal—the average gap to optimal results is 0.26% and 5.15% in the case of evolutionary and Tabu Search methods, respectively.     

基于P2P的流媒体技术

现有的流媒体系统一般是基于客户／服务器模式和IP组播技术,这限制了用户数量且IP组播需先得到ISP支持,故其发展受到很大限制。而在P2P网络中,每个接收数据的用户同时向外转发数据,这就充分利用了以往忽视的客户机资源。首先指出了P2P流媒体应用中所面临的挑战,并着重从应用层多播树、网络异构性、激励机制等方面阐述了P2P流媒体的研究现状,分析讨论了存在的问题,最后指出进一步的研究方向。     

一种基于混沌加密算法的保密视频会议方案及实现

针对目前混沌加密算法重于理论研究的现实,结合P2P网络传输结构的安全隐患,以Windows Peer-to-Peer Networking平台的Graph模块为基础,设计了一种运用混沌加密算法进行通信数据加密的P2P保密视频会议方案。方案在P2P网络结构采用CA机制,在网络传输结构上层采用混沌加密算法以及动态密钥管理,构建视频会议的安全环境。在实现该方案基础上探索了混沌加密算法的可用性。     

一种基于P2P的视频共享系统的研究与实现

视频点播(VOD)是一种以用户为主导的音视频信息系统。传统的VOD系统多是C/S模式采用服务器机群或者代理缓存的方式来实现,这会带来较大的硬件和管理开销,系统扩展性也难以得到保证。文中提出了一种基于P2P结构的视频点播的设计方案,分析了采用P2P技术以后视频点播系统对于节点闲散资源的利用和保证播放质量等方面的优势,并探讨了在系统设计与实现中的相关技术与方法。     

Packet loss probability for DiffServ over IP and MPLS reliable homogeneous multicast networks

Multicasting has become increasingly important with the emergence of Internet-based applications such as IP telephony, audio/video conferencing, distributed databases and software upgrading. IP multicasting is an efficient way to distribute information from a single source to multiple destinations at different locations. In practice IP is considered as a layer 3 protocol. Multiprotocol Label Switching (MPLS) replaces the IP forwarding by a simple label lookup. MPLS combines the flexibility of layer 3 routing and layer 2 switching.In order to provide QoS in group communications for real time applications such as video conferencing, reliable multicasting is used. Miscellaneous efforts have been undertaken to provide reliability on top of IP multicast. Two error control strategies have been popular in practice. These are the FEC (Forward Error Correction) strategy, which uses error correction alone, and the ARQ (Automatic Repeat Request) strategy, which uses error detection, combined with retransmission of data.In this paper, we present a new fair share policy (FSP) that utilizes Differentiated Services to solve the problems of QoS and congestion control when reliable ARQ multicast is used. The results should provide insight into the comparisons of the residual packet loss probability between IP multicast in MPLS networks using FSP and plain IP multicasting using the same policy when DiffServ are adopted and when reliable ARQ multicast is considered.