内容分发网络中带容量和能力约束的副本放置问题研究

副本放置问题是内容分发网络中的一项关键技术,已有的副本放置模型未考虑服务器的负载能力,本文研究考虑了基于内容分发网络服务器存储容量约束与服务能力约束的副本放置问题,建立了双约束的副本放置模型,设计了贪婪算法,把两阶段的模型求解转化成求解一系列的单服务器节点的最小费用流模型,获得了副本放置策略和用户请求重定向策略,并分析了算法的复杂性。     

CDN网络中一种新的负载平衡技术

研究提高网络性能的问题,为了解决现有CDN网络中的负载平衡技术中用户的请求不能立刻得到响应的问题,提出了一种分布式装箱策略的负载平衡算法,算法可以充分利用网络拓扑信息和文件访问历史以及服务器的负载信息,构建一个完善、全面的中间层,并利用缓存、复制、负载平衡和DNS重定向等技术,实现对网络流量和各节点的负载实时处理.通过改进技术的仿真实验证明,分布式装箱策略完成了网络用户的请求导向最近的服务节点靠近,使得用户所需要的内容及时的分发,并可以缓解网络堵塞问题,提高用户访问网站的响应速度.     

用户需求感知的D2D视频分发机制

针对目前的D2D多播内容分发机制因冗余传输过高而导致簇头节点能量效率以及系统频谱效率低的问题,提出了一种基于用户需求感知的D2D视频分发机制。通过对用户视频服务请求进行预测,在为服务请求用户分发视频的同时将视频推送给潜在服务用户。首先,根据用户的兴趣、视频的流行度以及用户设备的剩余能量等估算出潜在服务用户接受视频推送的意愿;其次,提出视频分发服务效用值度量来衡量视频分发服务的价值,并对最优化簇头能量效率问题进行建模;最后,提出最优化簇头能量效率的D2D视频分发机制。实验结果表明所提出的D2D视频分发机制相较于传统分发机制其簇头的能量效率及系统吞吐量有着明显的优势。     

基于Web内容的集群服务器请求分配系统的研究与实现

随着基于Internet上的Web应用服务迅速发展，提供高性能、高可靠性和高扩展性的各种Web服务已成为用户的迫切需求。通过对现有的请求分配策略的分析，提出一种综合考虑后端服务器的缓存局域性的基于Web请求内容的集群服务器负载分发策略的设计与实现。     

基于Web的内容的集群服务器请求分配系统的研究与实现

随着基于Internet上的Web应用服务迅速发展，提供高性能、高可靠性和高扩展性的各种Web服务已成为用户的迫切需求，通过对现有的请求分配策略的分析，提出一种综合考虑后端服务器的缓存局域性的基于Web请求内容的集群服务器负载分发策略的设计与实现。     

基于播存结构的雾架构内容协同分发机制

雾计算是一种将云服务推向用户边缘的计算范型,其主要采用用户被动拉取内容的方式来加速内容分发,缺乏主动推送能力。因此,提出利用具备主动推送力度强的播存结构来辅助雾架构以实现内容的主动推送。在此基础上,针对边缘内容协同分发,提出一种基于软件定义的内容协同分发机制,具体包括多粒度协同存储机制、软件定义策略和域内多节点协同策略。最后利用原型系统进行实验测试与结果分析,结果验证该机制能够高效减少用户请求时延,提升用户体验。     

基于Linux的FTP服务向内部网络定向的设计分析与实现

访问内部网络中服务器的一种方法是在外部服务器(或网关)上进行重定向远程的访问请求。本文以FTP服务的重定向为例分析了两种重定向机制,并在Linux上进行了实现。这两种机制一个是使用socket层透明代理,另一个是利用NAT(NetworkAddress Translate)。     

媒体分发网络存储策略优化

针对媒体分发网络（MDN）系统中现有媒体分发存储策略所存在的问题,为进一步提高系统的性能和满足更多用户的点播请求,提出一种基于分块的存储策略,该策略通过对每部影片进行分块及对所有影片块定期进行热度的排序决定MS和PN所需存储的相应影片内容。通过NS2仿真平台所搭建的MDN系统进行实验验证表明,该存储策略能够更好地改进用户点播请求的响应时间及本地数据击中率。     

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。     

一种面向边缘计算环境的去中心化服务请求分发方法

边缘计算模式的出现使得软件服务可以部署在距离用户较近的边缘服务器上,从而减小服务调用过程中产生的数据传输开销,并提升服务质量.然而,由于计算和存储等资源的限制,边缘服务器通常只能部署有限数量的服务实例,无法满足复杂多样的服务请求,加之边缘计算环境下服务请求分布不均导致了边缘服务器之间负载的不均衡性.因此,边缘计算环境下需要对服务请求进行再分配来满足不同的服务请求并优化服务供应.如何合理地将服务请求分发到合适的边缘服务器以优化系统的负载均衡并提升服务质量成为亟待解决的关键问题.现有的研究方法通常采用集中式的方法来解决该问题,存在单点故障等严重缺陷.因此,本文基于博弈理论设计了一种面向边缘计算环境的去中心化服务请求分发方法.该方法将边缘服务器间的服务请求分发问题建模为分布式的非合作博弈模型,通过多轮次的博弈和竞争达到系统的Nash均衡状态,以此获取服务请求的分发策略.实验结果表明,本文所提出的方法可以有效优化边缘服务器之间的负载均衡,降低服务的响应时间,并且随着系统规模的扩大表现出良好的可扩展性.     

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 .     

基于域名系统知识图谱的CDN域名识别技术

内容分发网络(content delivery network,CDN)是互联网上的重要基础设施,目前识别CDN域名的方法主要利用域名字符特征、HTTP关键字和DNS记录等,识别范围有限.针对大规模识别CDN域名的问题,提出了基于域名系统知识图谱的CDN域名识别技术.根据域名系统的特征进行本体建模、数据获取、知识图谱构...     

Improving the resilience of content distribution networks to large scale distributed denial of service attacks

Distributed Denial of Service (DDoS) attacks remain a daunting challenge for Internet service providers. Previous work on countering these attacks has focused primarily on attacks at a single server location and the associated network infrastructure. Increasingly, however, high-volume sites are served via content distribution networks (CDNs). In this paper, we propose two mechanisms to withstand and deter DDoS attacks on CDN-hosted Web sites and the CDN infrastructure. First, we present a novel CDN request routing algorithm which allows CDN proxies to effectively distinguish attacks from the requests from actual users. The proposed scheme, based on the keyed hash function, can significantly improve the resilience of CDNs to DDoS attacks. In particular, the resilience of a CDN, consisting of n proxies, becomes O(n²) with the proposed approach, when compared to a site hosted by a single server. We present performance numbers from a controlled test environment to show that the proposed approach is effective. Second, we introduce novel site allocation algorithms based on the well-established theory on binary codes. The proposed allocation algorithm guarantees an upper bound on the level of service outage of a CDN-hosted site even when a DoS attack on another site on the same CDN has been successful. Together, our schemes significantly improve the resilience of the Web sites hosted by CDNs, and complement other work on countering DoS.     

Automated Bidding for Media Services at the Edge of a Content Delivery Network

We investigate the problem of providing media services to multiple autonomous wireless users at the edge of a content delivery network (CDN) in a setting where wireless resources are priced based on real-time market demands. Our focus is on the multimedia service resource negotiation process, which is performed prior to the actual media transmission. We adopt the progressive second price (PSP) auction mechanism, which is used to determine the network resource allocation to the users and a corresponding tax for the consumed resources. Our interest in this negotiation mechanism lies in understanding a single user's (or agent's) ability to learn to improve its bids over time in order to increase its own utility in the face of time-varying resource valuations and contention for resources with other users. We pay particular attention to the implementation complexity and the information requirements of the agent's deployed learning rule, and we quantify the impact of these factors on the rule's ultimate performance (i.e., the cumulative utility achieved over time) and efficiency (i.e., the utility gained per unit of computation). These factors are especially important in the mobile video streaming context, where limited resources must be efficiently utilized, and where communication and computation overheads can significantly impact the quality of service experienced by the user.      

Content delivery networks: status and trends

CDNs improve network performance and offer fast and reliable applications and services by distributing content to cache servers located close to users. The Web's growth has transformed communications and business services such that speed, accuracy, and availability of network-delivered content has become absolutely critical - both on their own terms and in terms of measuring Web performance. Proxy servers partially address the need for rapid content delivery by providing multiple clients with a shared cache location. In this context, if a requested object exists in a cache (and the cached version has not expired), clients get a cached copy, which typically reduces delivery time. CDNs act as trusted overlay networks that offer high-performance delivery of common Web objects, static data, and rich multimedia content by distributing content load among servers that are close to the clients. CDN benefits include reduced origin server load, reduced latency for end users, and increased throughput. CDNs can also improve Web scalability and disperse flash-crowd events. Here we offer an overview of the CDN architecture and popular CDN service providers.     

混合内容分发网络及其性能分析模型

在大规模数字内容网络分发方面,占主导地位的CDN(Content Delivery Network)和P2P(Peer-to-Peer)网络具有显著互补优势.CDN网络可降低数据传输延迟,提高用户体验;P2P网络的部署成本低,可扩展性强.文章提出一种基于CDN和PZP技术的混合内容分发网络(Hybrid Content Distribution Network,HCDN),在骨干网部署CDN系统,在接入网构建P2P区域化网络,终端用户可同时通过CDN和P2P网络获取数据;阐述了HCDN网络模型及其内容分发处理流程,包括内容路由、副本放置和数据下载;给出了基于流模型的混合网络性能模型,并从节点数量变化、下载时间、服务能力和传输开销等方面进行综合性能评价.实验结果表明,HCDN能提高下载速率、降低服务器负载以及减小骨干网传输流量,既可克服CDN网络部署成本高的缺点,也可避免P2P网络在节点数量稀缺时的低性能.     

Direct push–pull or assisted push–pull? Toward optimal video content delivery using shared storage-based cloud CDN (SS-CCDN)

Video content delivery networks face many challenges such as scalability, quality of service and flexibility. Video suppliers address them through CDN. Cloud computing and Video content Delivery as a Service (VDaaS) plays a key role in improving the content delivery standard and makes the work of content providers, easier. By hosting video contents in the cloud, the content delivery costs are minimized and the overall content delivery performance enhanced by optimization of cloud CDN. Cost optimization of the cloud-based content delivery network requires a focus on delay or throughput, the overall performance and content delivery. The content placement and content access, the QoS and the QoE in CDN can be improved by enhancing the video content delivery performance. In this paper, a unique model for video content delivery, cloud-based is developed, titled as shared storage-based cloud CDN (SS-CCDN) to achieve the objective. This design optimizes through algorithms, the effective placement of video data and dynamic update of video data. For analysis, GA, PSO, and ACO algorithms are used. The proposed model uses direct and assisted push–pull content delivery schemes for cost-efficient content delivery. The low-cost VDaaS model reduces the storage cost, keeps the latency and the traffic cost. Experimental results validate that this model, with regard to storage, traffic, and latency generate higher performance with lower price and satisfy the QoS and QoE aspects in content delivery.

     

IPTV建设中的两个关键技术问题及其解决方案

针对IPTV系统的试点建设中,遇到的诸多直接关系到用户体验质量、组网成本以及规模应用等技术问题,在对其中的两个关键问题———节点存储问题和直播业务的QOS问题进行探索的基础上,通过对几种常见的CDN节点存储方案所进行的性能与成本分析对比,得出了SAN方案是最佳选择的结论。随后,对影响直播业务QOS的两个关键问题———频道切换和组播丢包问题进行了深入的分析,并据此提出了切实可行的解决方案。     

一种基于云存储的VOD系统

针对VOD视频点播系统在高并发网络访问情况下的I/O瓶颈、网络拥塞等问题,提出一种基于云存储的解决方案。在VOD现有架构的基础上,采用云存储和CDN网络提供存储和访问服务,提高了系统的高并发访问负载能力。同时针对VOD视频转码模块提出一种基于FFMPEG的整体解决方案,能在实际应用中有效降低技术难度和开发成本,对VOD系统的优化和提升具有实际意义和应用价值。     

基于边缘缓存的下载加速方案设计与实现

针对传统网络拥塞导致网络下载速度过慢等一系列问题,文章通过对内容分发网络和P2P技术的研究,提出了一种基于边缘缓存的下载加速方案。该方案将P2P技术引入内容分发网络,利用各自优点,构建一个新型资源下载服务系统。将中心服务器上的资源推送至网络边缘,缩短了用户和资源的距离。同时,让边缘缓存服务器与邻近用户自发组建P2P下载网络,将资源更加边缘化,通过就近获取资源,提高下栽速度。实验表明,该方案不仅可以有效提高下栽速度,而且可以有效控制骨干网的网络流量。