基于Web 2.0的智能内容分发网络(ICDN)研究初探

Web 2.0时代下,基于C/S的系统模型将受到挑战,作为网络结构的边缘点的Client将与Server越来越对等化,基于P2P的网络将大大提升网能放大作用,但是其无序性特征却给电信骨干网带来较大冲击。新兴的内容分发网络(CDN,Content Delivery Network)虽然具有较强的结构化特点,但是其放大能力受扩展成本的限制。本文针对这两种结构互异网络的优劣势,在CDN网络基础上,融合了Web 2.0理念,提出了ICDN(Intelligent Content Delivery Network)网络概念,并给出了边缘融合、中心融合和混合融合等三种模型。最后,对该网络结构模型的应用进行了展望。     

基于P2P和CDN的混合流媒体分发模型及分析*

在CDN和P2P两种主流的流媒体分发技术的基础上,提出了基于系统流量的混合流媒体分发模型,根据系统中节点数量和媒体流量之间的关系,在CDN自治域内实现CDN和P2P的混合式服务,并对上述理论进行了仿真。实验结果表明,与传统的CDN和P2P相比,新的混合模型既可以减少主干网络的流量,又能在不降低流媒体质量的情况下,有效降低CDN服务器压力,减少系统的响应时间,提高网络利用率。     

新型双重混合的流媒体直播系统架构

研究内容分发网络(CDN)与对等网络(P2P)的混合模型,提出一种CDN与P2P、树形结构与网状结构双重混合的流媒体直播系统架构。设计基于CDN-P2P的树网结合直播系统模型,阐述核心树的主要构建机制,介绍网状结构的节点选择算法。系统仿真结果表明,与纯P2P模型及CDN-P2P混合模型相比,该系统的播放和启动延迟较小。     

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.     

混合内容分发网络的流媒体监控系统研究与实现

介绍一种应用于视频监控系统的混合内容分发网络HyCDN.该网络结合了CDN和P2P的互补优势,将P2P扩展性强的优点结合到稳定的CDN架构中.混合网络的域间利用边缘服务器相对稳定的特点结合了P2P应用层组播的树型分发技术;混合网络域内的逻辑拓扑的构造则是糅合了P2P树状拓扑和随机拓扑的特点,改善了节点动态性引发的问题并降低终端用户观看视频的延迟.文章详细阐述了在混合网域间和域内的技术思路和处理流程以及缓冲区的管理技术.利用仿真实验对系统的有效性进行分析.实验表明,该网络既克服了树状拓扑结构中节点动态性带来的数据传输延迟大的缺点,又较随机拓扑结构减少了控制开销.     

基于流媒体服务的IP网络内容分发系统的设计

IP网络中数据量巨大的流媒体内容使服务器和骨干网络承受的压力越来越大。内容分发系统对保证流媒体QoS起到至关重要的作用。该文通过分析内容分发网络(CDN)和P2P两种新型内容分发技术，提出了多源网状散列式P2P模型和一种改进的内容缓存算法，设计了基于CDN和P2P技术的内容分发系统。系统可同时满足请求多和请求少的情况，提高了流媒体QoS。     

基于P2P流媒体实时分发模型的异常探测研究

CDN和P2P是现在常用的两种网络加速方法。本文首先简要阐述了CDN和P2P技术,然后针对CDN-P2P混合流媒体分发模型给出了一种探测异常节点的方案。此方案在一定程度上减轻了CDN服务器作为P2P索引节点的监测压力,从而使CDN服务器能更有效地进行流媒体服务。     

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.     

网通IDC部署CDN

中国网通的网络型数据中心——i-DXnet 建立了基于其宽带骨干网的内容快速分发网络(CDN),并籍此推出其CDN 服务。i-DXnet 所建立的“内容快速分发网络”在网通现有的 IP 网络基础上增加一层新的网络架构,进而实现以“内容”为核心的策略化管理。它将通过网通的骨干网寻找与用户需求相对应的最恰当的站点、最恰当的服务器。内容缓存设备为用户提供“快速内容分发”的增值服务,以此来提高用户访问网站的响应速度,提升网络接通的稳定性。由于网络型数据中心的 CDN 服务的基本原理是在分布各地的数据中心的节点上部署客户最经常访问的数据,因此可简化对互联网传输     

一种基于CDN和P2P的流媒体内容分发网络模型

对等网络流媒体技术可以合理地利用客户端的计算机能力和带宽资源,因此,P2P流媒体分发系统成为P2P技术领域内重要应用之一设计一个结合P2P技术和CDN技术的流媒体内容分发网络模型,该模型能更好地减少高度动态性对节点播放的影响,为普通节点提供更好的服务     

结合CDN与P2P技术的混合流媒体系统研究

对基于CDN和P2P的流媒体系统进行了分析对比,指出了它们各自的优缺点,并根据因特网的结构特点,给出了一种结合这两种技术的混合流媒体系统的设计方案,提出了客户机端的内容缓存替换问题并给出了一种替换算法,对客户机离线的随机性与频繁性问题,文中给出了一种新的失效服务节点的快速替换查找策略。     

Building a peer-to-peer content distribution network with high performance,scalability and robustness

Content distribution networks (CDN) are fundamental, yet expensive technologies for distributing the content of web-servers to large audiences. The P2P model is a perfect match to build a low-cost and scalable CDN infrastructure for popular websites by exploiting the underutilized resources of their user communities. However, building a P2P-based CDN is not a straightforward endeavor. In contrast to traditional CDNs, peers are autonomous and volunteer participants with their own heterogeneous interests that should be taken into account in the design of the P2P system. Moreover, churn rate is much higher than in dedicated CDN infrastructures, which can easily destabilize the system and severely degrade the performance. Finally and foremostly, while many P2P systems abstract any topological information about the underlying network, a top priority of a CDN is to incorporate locality-awareness in query routing in order to locate close-by content. This paper aims at building a P2P CDN with high performance, scalability and robustness. Our proposed protocols combine DHT efficiency with gossip robustness and take into account the interests and localities of peers. In short, Flower-CDN provides a hybrid and locality-aware routing infrastructure for user queries. PetalUp-CDN is a highly scalable version of Flower-CDN that dynamically adapts to variable rates of participation and prevent overload situations. In addition, we ensure the robustness of our P2P CDN via low-cost maintenance protocols that can detect and recover from churn and dynamicity. Our extensive performance evaluation shows that our protocols yield high performance gains under both static and highly dynamic environments. Furthermore, they incur acceptable and tunable overhead. Finally we provide main guidelines to deploy Flower-CDN for the public use.     

内容分发网络性能测量方法研究与实现

内容分发网络 (CDN)是新型的网络加速技术 .提出了一种新的 CDN性能测量方法 :将 CDN性能测量融入到网络测量基础设施之中 ,CDN提供者、内容提供者或终端用户可以根据需要随时、方便的测量、评价 CDN性能 ,克服了以往测量方法测量周期长、测量规模扩展性差以及数据资源利用率低等缺点 .基于此方法 ,设计并实现了一个集成在 CNMI下的 CDN性能测量系统 :CDNPMS,系统使用灵活简单 ,可以从 CDN外部测量用户感知的 (Client- perceived) CDN性能 ,并且用此系统对目前最大的 Akamai CDN进行了成功测量 .     

CDN中基于节点度的网络编码策略

在使用网络编码的基于重叠网络的内容分发网络中,针对节点的选择问题,提出使用节点度所决定的概率来选择邻居节点的策略,仿真实验结果表明,该策略可以改进对网络中节点间带宽的利用率,加快内容分发的过程,与现有策略相比,各种性能都有不同程度的提高。     

Analysis of a CDN–P2P hybrid architecture for cost-effective streaming media distribution

To distribute video and audio data in real-time streaming mode, two different technologies – Content Distribution Network (CDN) and Peer-to-Peer (P2P) – have been proposed. However, both technologies have their own limitations: CDN servers are expensive to deploy and maintain, and consequently incur a cost for media providers and/or clients for server capacity reservation. On the other hand, a P2P-based architecture requires sufficient number of seed supplying peers to jumpstart the distribution process. Compared with a CDN server, a peer usually offers much lower out-bound streaming rate and hence multiple peers must jointly stream a media data to a requesting peer. Furthermore, it is not clear how to determine how much a peer should contribute back to the system after receiving the media data, in order to sustain the overall media distribution capacity.In this paper, we propose and analyze a novel hybrid architecture that integrates both CDN- and P2P-based streaming media distribution. The architecture is highly cost-effective: it significantly lowers the cost of CDN capacity reservation, without compromising the media quality delivered. In particular, we propose and compare different limited contribution policies for peers that request a media data, so that the streaming capacity of each peer can be exploited on a fair and limited basis. We present: (1) in-depth analysis of the proposed architecture under different contribution policies, and (2) extensive simulation results which validate the analysis. Our analytical and simulation results form a rigorous basis for the planning and dimensioning of the hybrid architecture.     

一种基于哈希表和Trie树的快速内容路由查找算法

内容分发网络CDN(Content Delivery Network)是一个建立并覆盖在互联网之上的一层特殊网络,专门用于通过互联网高效传递丰富的多媒体内容.与传统的网络一样,要求核心路由器每秒能转发几百万个以上的分组,而实现高速分组转发的关键是路由表的组织和快速的路由查找算法.首先概述了内容路由网络的背景,罗列出了几种常见的路由查找算法,并在此基础上,引入基于Hash和Trie树的路由查找算法,最后在试验的基础上对平均查找时间、平均查找次数以及最大匹配次数进行了比较分析,试验结论显示该算法缩短了查找时间,提高了系统性能.     

Design, optimization and performance evaluation of a content distribution overlay for streaming

As an evolution of peer-to-peer (p2p) file-sharing applications, overlay-based networks are also adopted to efficiently distribute content with real-time constraints to a wide user population. In addition, they can be utilized to exploit application level strategies to overcome limitations imposed by the underlying network infrastructure, e.g., the lack of multicast support.In this perspective, the paper introduces an overlay Content Distribution Network (CDN) able to sustain the real-time delivery of data streams. To better use resources, and to face the churn affecting users, the control and optimization of the CDN are performed through a model predictive control scheme. Simulations of two use cases are provided to show the effectiveness of the proposed solution. In particular, the stream of multimedia and interactive grid data are considered.     

Envy-Free Resource Allocation and Request Routing in Hybrid CDN–P2P Networks

Hybrid CDN–P2P networks (HCDNs) combine Peer to Peer (P2P) networks and Content Delivery Networks (CDN) to benefit from their complementary advantages. In order to enable a traditional CDN to offer hybrid content delivery service, we introduce a resource scheduling mechanism to perform the request routing process and determine the desired level of contribution for users. The proposed mechanism relies on a truthful, profit maximizing, envy-free auction to optimize contributions of the end-users in P2P content delivery. Based on the proposed solution, economics of content delivery in the HCDN are studied and it is shown that through our resource scheduling mechanism, it is possible to serve a big fraction of end-users with higher quality content, increase the net profit of the HCDN provider, and decrease expenditures of the content provider simultaneously.     

基于Web访问特性的缓存替换策略

在分析Web轨迹的基础上,找出用户访问Web内容的访问特性:访问再次到达的概率和访问内容大小分布,并建立相应的代价公式,利用这些代价作为计算Web内容价值的要素.根据这些特性判断用户访问内容被再次访问的可能性,提出内容分发网络缓存替换策略.最后通过数值仿真计算与现有替换策略进行比较,说明了该替换策略的优越性.