Evolution and challenges of DNS-based CDNs

DNS-based server redirecting is considered the most popular means of deploying CDNs. However, with the increasing use of remote DNS, DNS-based CDNs face a great challenge in performance degradation. To address this issue, encouraging progress has been made in both industry and research communities. In this article, state-of-art solutions for the remote DNS problem are discussed at first. Next, privacy concerns about DNS-based CDNs, including client location as well as redirection privacy, are identified and a representative solution is summarized. Finally, the solution is compared to those in prior works under different measures, and a discussion on DNS-based CDN applications is provided. A model is also established to deepen the understanding of CDN performance. We believe that this survey will shed light on the application of DNS-based CDNs, and it is expected to provide design guidelines to CDN service providers.     

互联网自治的改造实现

本文的自治互联网技术结合互联网现实,通过现有域名体系构造出自主自治的可扩展域名体系和层次结构,并提供自治网络系统内/间的域名解释机制,甚至可以单边行动的方式实现互联网自治的过渡和改造。     

新型壳聚糖/DNS杂化材料的制备及对重金属Pb2+的吸附性能研究

在乙醚介质中,通过丁二酸酐与γ-氨丙基三甲氧基硅烷改性后的纳米SiO2(即可分散的纳米SiO2,简称DNS)反应,合成了羧基化的DNS,经过壳聚糖与羧基化的DNS脱水生成酰胺的过程,制备了壳聚糖/DNS杂化材料.通过红外光谱、扫描电镜和热重分析对杂化材料进行表征.研究了壳聚糖及杂化材料微粒吸附Pb2+时pH值、时间、用...     

多进程DNS服务器中通信方法的设计与实现

多进程技术是目前大型软件开发中降低复杂性的有效途径.针对BIND10服务器软件的开发提出一种基于安全socket的多进程通讯方法,其中包括一种多进程通信协议(MPCP),通讯接口CI和消息路由进程MRouter的设计.CI使用SSL协议来保障通信的安全性,MRouter使用消息寻址转发机制实现进程之间的点对点和点对多点通信.目前该设计已经在BIND10软件项目中应用并实现,能够完成各个进程模块的实时通讯、支持分布式部署、保证容错性和健壮性、便于扩展功能的实现等.     

DNS性能优化实践

通过对运营商网络DNS的逻辑架构、系统参数进行优化,在不增加硬件配置的条件下,大幅提升DNS的处理性能,节省硬件投资,达到节能减排、经济高效的目的。     

利用BIND实现多链路负载均衡访问

随着三大运营商的整合和国内电信业的发展,多链路的情况的出现,如何实现各链路的最优请求访问一直是困扰大家的一个难题,本文从实际工作经验出发,阐述了利用ISCBIND实现利用DNS对各链路请求实现智能DNS解析,以达到从最优链路访问的应用,并列举了一个获取ISP网段的脚本应用.     

DNS欺骗技术研究与实现

DNS欺骗攻击是攻击者常用的手法,它具有隐蔽性强、打击面广、攻击效果明显的特点。分析在以太网中利用对网络数据监听,来截获DNS报文,进而伪造DNS报文进行DNS欺骗的技术,并给出基于WinPcap的实现。     

An efficient block parallel AMR method for two phase interfacial flow simulations

The direct numerical simulation of two phase interfacial flows can be computationally challenging, as the strong resolution needed to follow the deformations of the interface leads to a lot of time spent solving the whole computation domain. Efficient solution of such problems requires an adaptive mesh refinement capability to concentrate computational effort where it is most needed. In this paper a parallel adaptive algorithm to solve incompressible two-phase flows with surface tension is presented: the AMR is handled with the help of the PARAMESH package. The free interface between fluids is tracked via Level Set approach; the jump conditions at the interface for pressure and velocity are imposed by the Ghost Fluid method. A multigrid preconditioned BiCG-stab solver adapted to the AMR data structure has been developed to allow high density ratio computations (up to 1:1000). Special treatment has been done at the refinement jumps to maintain the fine mesh accuracy. Computational results are compared in different test cases with analytical solutions or literature, and show very good agreement with the references. The effectiveness of PARAMESH parallelization has been quite well maintained, as shown in the strong and weak scaling tests. Speed-up capabilities of the AMR are demonstrated.     

省建DNS容灾体系的设计与实现

DNS作为互联网核心业务,其重要性不言而喻,随着运营商越来越多使用Anycast的组网结构承载DNS业务,DNS大都建设为双节点,双节点部署至不同的机楼,这样就可以起到异地容灾的作用。在正常的情况下,当单节点退服,另一节点可以起到替代的作用,但是如果节点没有完全退服,此时就需要人为地进行切换,并且会影响故障时长,笔者提出一种解决方案,可以通过配置来实现双节点的逻辑上的冗余,当节点发生故障时,无论是完全退服故障或是不完全退服,均可以实现DNS业务的双节点间的切换,并且做到用户无感知。     

基于日志统计特征的DNS隧道检测

以DNS服务器的日志为数据源,提取出二级域名的熵、子域名个数、缓存命中率等多维日志统计特征, 将日志量化为特征向量集;以特征向量集为数据源,使用随机森林算法进行模型训练,并使用十折交叉验证的方法对模型参数进行调整,对模型进行优化,提高整体检测精度;在不同分类算法下进行对比实验,并将实验结果与已有研究方法进行比较. 实验结果表明,提出的检测方法在召回率达到98.5%的情况下,有不低于90%的准确率,检测精度有所提高,即提出的算法能有效检测DNS隧道.