Architecture of the Mobile Environment for Intelligent Genetic Search and Proxy Caching

As the number of documents and servers on Internet grows with the enormous speed, it becomes necessary to design efficient algorithms and tools for search and retrieval of documents. Also, the number of accesses to servers on Internet constantly grows. Congestion of servers and links can be alleviated using proxy caches. Latency on Web can be reduced using prefetching and caching. Efficient search of documents can be done with improved genetic algorithm that exploits the principles of temporal and spatial locality. Mobile agents can be used to optimize network traffic for distributed applications. This paper describes several existing solutions to the problem and discusses the implementation of Java distributed object application for experimenting with genetic search and proxy caching algorithms for Internet.     

基于社会信任的恶意网页协防机制

针对恶意网页的威胁,提出了一种基于社会信任的分布式恶意网页协作防御机制：结合第三方专业服务机构提供的恶意网址列表,并利用社会网络中好友间的直接信任和间接信任获取好友对网页的评价信息,集成好友的安全浏览经验形成网页综合评价;每个用户都与其好友进行协作,形成一个网状的防御体系。实验结果表明,该机制能够有效减少恶意网页的访问量,提高社会网络防御恶意网页的能力。     

Optimizing the Number of Robots for Web Search Engines

Robots are deployed by a Web search engine for collecting information from different Web servers in order to maintain the currency of its data base of Web pages. In this paper, we investigate the number of robots to be used by a search engine so as to maximize the currency of the data base without putting an unnecessary load on the network. We use a queueing model to represent the system. The arrivals to the queueing system are Web pages brought by the robots; service corresponds to the indexing of these pages. The objective is to find the number of robots, and thus the arrival rate of the queueing system, such that the indexing queue is neither starved nor saturated. For this, we consider a finite-buffer queueing system and define the cost function to be minimized as a weighted sum of the loss probability and the starvation probability. Under the assumption that arrivals form a Poisson process, and that service times are independent and identically distributed random variables with an exponential distribution, or with a more general service function, we obtain explicit/numerical solutions for the optimal number of robots to deploy.     

Web应用的安全现状与防护技术研究

随着互联网技术的发展,Web技术得到了日益广泛的应用,越来越多基于Web应用的系统被部署在互联网上以提供各式各样的服务,由于互联网本身的开放性使其时刻面临着潜在恶意攻击,其安全性问题日益突出。在这样的背景下,进行Web应用安全现状与防护技术的研究具有很强的现实意义,为了提高Web安全性,建立健全Web防护体系,这里从客户端、服务器端和传输三方面对当今Web应用所面临的安全成胁进行了系统地分析,并针对各自面临的常见安全威胁提出了相应的安全防护方案和防护建议。     

Internet Web servers: workload characterization and performanceimplications

This paper presents a workload characterization study for Internet Web servers. Six different data sets are used in the study: three from academic environments, two from scientific research organizations, and one from a commercial Internet provider. These data sets represent three different orders of magnitude in server activity, and two different orders of magnitude in time duration, ranging from one week of activity to one year. The workload characterization focuses on the document type distribution, the document size distribution, the document referencing behavior, and the geographic distribution of server requests. Throughout the study, emphasis is placed on finding workload characteristics that are common to all the data sets studied. Ten such characteristics are identified. The paper concludes with a discussion of caching and performance issues, using the observed workload characteristics to suggest performance enhancements that seem promising for Internet Web servers     

Hash routing for collections of shared Web caches

Shared Web caches, also referred to as proxy Web servers, allow multiple clients to quickly access a pool of popular Web pages. An organization that provides shared caching to its Web clients will typically have a collection of shared caches rather than just one. For collections of shared caches, it is desirable to coordinate the caches so that all cached pages in the collection are shared among the organization's clients. In this article we investigate two classes of protocols for coordinating a collection of shared caches: the ICP protocol, which has caches ping each other to locate a cached object; and the hash routing protocols, which place objects in the shared caches as a function of the objects' URLs. Our contribution is twofold. First, we compare the performance of the protocols with respect to cache-server overhead and object retrieval latency; for a collection of shared caches, our analysis shows that the hash-routing schemes have significant performance advantages over ICP for both of the performance metrics. The existing hash-routing protocols assume that the cache servers are homogeneous in storage capacity and processing capability, even though most collections of cache servers are vastly heterogeneous. Our second contribution is to extend a robust hash-routing scheme so that it balances requests among the caches according to any desired distribution; the extended hash-routing scheme is robust in the face of cache failures, is tunable for heterogeneous caches, and can have significant performance advantages over ICP     

Efficient WISH in an indoor environment

With the diffusion of wireless connections to Internet, the number of complex operations carried out from mobile users is increasing. To cope with bandwidth limitations and with disconnections, data caching is the most used technique. However for complex operation like dynamic searching a better solution is to take advantage of the multichannel property offered by CDMA protocol. In this case, cached documents can be allocated on distinguished channels in a dynamic way to obtain a better utilization of the radio communication links. We study a particular caching strategy suitable to be integrated with a radio-channel policy. We consider a semantic caching for intranet queries (or intranet searching) that takes advantage of data semantics by caching query answers instead of pages in order to exploit similarities between different queries. In fact, in a WLAN scenario, Internet activity is frequently composed by intranet searching operations characterized by local queries that aim to explore documents stored in a neighbor of the home site. We study benefits from a channel allocation strategy applied to intranet searching with semantic caching. Simulation experiments are carried out by considering an indoor scenario model where mobile clients perform keyword-based queries answered by local Web servers running application we refer to as WISH (Wireless Intranet SearcHing), an intranet searching tool based on semantic caching. The results show a 12% improvement in radio channel usage for 20% of users that share cached documents.     

Visualizing the structure of Web communities based on data acquired from a search engine

Discovery of Web communities, groups of Web pages sharing common interests, is important for assisting users' information retrieval from the Web. This paper describes a method for visualizing Web communities and their internal structures. visualization of Web communities in the form of graphs enables users to access related pages easily, and it often reflects the characteristics of the Web communities. Since related Web pages are often co-referred from the same Web page, the number of co-occurrences of references in a search engine is used for measuring the relation among pages. Two URLs are given to a search engine as keywords, and the value of the number of pages searched from both URLs divided by the number of pages searched from either URL, which is called the Jaccard coefficient, is calculated as the criteria for evaluating the relation between the two URLs. The value is used for determining the length of an edge in a graph so that vertices of related pages will be located close to each other. Our visualization system based on the method succeeds in clarifying various genres of Web communities, although the system does not interpret the contents of the pages. The method of calculating the Jaccard coefficient is easily processed by computer systems, and it is suitable for visualization using the data acquired from a search engine.     

移动宽带用户恶意攻击流量处置方法的研究

在总结移动互联网的发展现状和其所面临的安全威胁的基础上,分析宽带用户被控后制造的恶意攻击流量攻击威胁,并提出了一种基于Radius和流量清洗系统处置被控用户恶意攻击流量攻击的方法,从源头抑制异常流量,有效防控互联网用户恶意攻击流量。     

Efficient complementary caching for ISP-aware networks

Internet service providers(ISPs) have taken some measures to reduce intolerable inter-ISP peer-to-peer(P2P) traffic costs,therefore user experiences of various P2P applications have been affected.The recently emerging offline downloading service seeks to improve user experience by using dedicate servers to cache requested files and provide high-speed uploading.However,with rapid increase in user population,the server-side bandwidth resource of offline downloading system is expected to be insufficient in the near future.We propose a novel complementary caching scheme with the goal of mitigating inter-ISP traffic,alleviating the load on servers of Internet applications and enhancing user experience.Both architecture and caching algorithm are presented in this paper.On the one hand,with full knowledge of P2P file sharing system and offline downloading service,the infrastructure of complementary caching is designed to conveniently be deployed and work together with existing platforms.The co-operational mechanisms among different major components are also included.On the other hand,with in-depth understanding of traffic characteristics that are relevant to caching,we develop complementary caching algorithm with respect to the density of requests,the redundancy of file and file size.Since such relevant information can be real-time captured in our design,the proposed policy can be implemented to guide the storage and replacement of caching unities.Based on real-world traces over 3 months,we demonstrate that the complementary caching scheme is capable to achieve the ’three-win’ objective.That is,for P2P downloading,over 50% of traffic is redirected to cache;for offline downloading,the average server-dependence of tasks drops from 0.71 to 0.32;for user experience,the average P2P transfer rate is increased by more than 50 KB/s.     

Cheetah: a space-efficient HNB-based NFAT approach to supporting network forensics

The popularity of the Internet has increased the ease of online access to malicious software, and the amount of software designed to perform denial-of-service (DoS) attacks is incalculable. This enables hackers to use online resources to easily launch attacks, posing serious threats to network security. The ultimate solution to increasingly severe DoS attacks is to identify the sources of the attacks; this is known as an IP traceback or forensics. However, the Network Forensic Analysis Tool is limited by the storage space, which significantly reduces the effects of the traceback. We proposed a Cheetah mechanism, which was proposed to overcome the disadvantage of requiring a significant data storage requirement. This involved using mechanic learning to filter irrelevant data, thereby retaining only the evidence related to DoS attacks to perform subsequent tracebacks. The experiment results confirmed that the proposed mechanism can reduce the quantity of data that requires storage and maintain a certain level of forensic accuracy.     

Took a licking, kept on ticking [Internet security]

A mysterious assault on its root server system left the Internet unscathed, but chastened. At almost exactly 9 p.m. GMT on 21 October, the Internets 13 root servers started to receive about 10 times their normal traffic. Unknown digital assailants had taken control of other machines on the Internet, making them send a flood of packets that threatened to overwhelm the root servers. Had the attack succeeded, the Web and e-mail would have gradually become unusable. While four of the servers, all in the United States, saw virtually no disruption, the other nine, including the three overseas, failed to respond to legitimate queries for at least a few minutes. The people who run the domain name system say they learned a lot from the October episode. They want lower-level name servers to do even more caching, perhaps of the entire root server database, and for longer than two days. Root server operators also must make sure their own networks are in good working order.     

Proxy caching for media streaming over the Internet

Streaming media has contributed to a significant amount of today's Internet traffic. Like conventional Web objects (e.g., HTML pages and images), media objects can benefit from proxy caching; but their unique features such as huge size and high bandwidth demand imply that conventional proxy caching strategies have to be substantially revised. This article discusses the critical issues and challenges of cache management for proxy-assisted media streaming. We survey, classify, and compare the state-of-the-art solutions. We also investigate advanced issues of combining multicast with caching, cooperating among proxies, and leveraging proxy caching in overlay networks.     

计算机网络信息安全防护方法策略探讨

计算机网络具有形式多样性、终端分布不均匀、开放性等特点,使得网络比较容易受到黑客、病毒、容易软件等的攻击,原本就十分脆弱的互联网在这种情况下越发显得不安全.针对来自互联网的安全威胁,如何确保信息的安全性已经成为人们所关注的重点问题.本文阐明了计算机网络信息的潜在威胁,分析了导致网络安全受到威胁的主要影响因素,针对如何加强网络安全防护提出合理建议.     

No longer in denial [network security]

The world was made rudely aware of the battle between hackers and Internet system security administration when public access to the sites of Amazon, eBay, Yahoo!, and other dot-coms was cut off by a new method of attack called distributed denial of service (DDoS), in February 2000. To block the sites, one or more hackers sneaked into the computers of several unsuspecting users connected to the Net, and used these widely dispersed machines as drones to launch a barrage of false messages. DDoS is a network problem because it abuses the network's resources; so the solution has to be in the network. Security experts are planning to fight the war with DDoS hackers on many fronts-from the Web-server vanguard through to the personal computers in the trenches. In the wake of the February attack, their first act has been to try to establish lines of communications among Web site operators, Internet service providers (ISPs), and legal authorities. The work of the Internet Engineering Task Force in tacking the hacker by tracking the flow of data packets through the network     

Efficient web content delivery using proxy caching techniques

Web caching technology has been widely used to improve the performance of the Web infrastructure and reduce user-perceived network latencies. Proxy caching is a major Web caching technique that attempts to serve user Web requests from one or a network of proxies located between the end user and Web servers hosting the original copies of the requested objects. This paper surveys the main technical aspects of proxy caching and discusses recent developments in proxy caching research including caching the "uncacheable" and multimedia streaming objects, and various adaptive and integrated caching approaches.     

互联网高级持续性威胁分析取证手段及技术研究

本研究主要对互联网高级威胁及原始流量分析手段及技术进行研究及分析,阐述了该方面研究的现状及主要技术手段,并说明了研究互联网高级威胁重点及难点主要是合理有效的分析手段。本文针对一种新型的、典型的互联网威胁分析系统,该系统针对原始流量进行采集和监控,对流量信息进行深度还原、存储、查询和分析,为及时掌握核心网络及系统的相关互联网安全威胁风险,以及检测漏洞、病毒、木马、网络攻击情况,发现网络安全事件的具体原因及可能存在的风险,对重大互联网安全威胁进行预警及预防,对互联网上存在的恶意行为及威胁进行溯源、分析、取证、处置及预防,提出了一种全新的解决思路,在保障重要信息系统的网络安全方面有了技术及理念性的创新。     

Distributed servers architecture for networked video services

In an on-demand video system, the video repository generally has limited streaming capacities and may be far from the users. In order to achieve higher user capacity and lower network transmission cost, distributed servers architecture can be used, in which multiple local servers are placed close to user pools and, according to their local demands, dynamically cache the contents streamed from the repository. We study a number of caching schemes as applied in the local servers depending on whether the repository is able to multicast movie contents to the local servers or not, and whether the local servers can exchange their cached contents among themselves or not. Our caching schemes keep a circular buffer of data for the movie requested, and hence movies are partially cached. By adjusting the size of the buffer, such caching is able to achieve better tradeoff between network channels and local storage as compared to the traditional caching in which a movie is treated as an entity. For each caching scheme, we study the tradeoff between the local storage and the network channels, and address how the total cost of the system can be minimized by appropriately sizing the buffer. As compared to a number of traditional operations (request batching and multicasting, true-VOD, etc.), we show that distributed servers architecture is able to achieve much lower system cost to offer on-demand video services     

语义搜索引擎概念模型

语义搜索引擎作为未来的万维网搜索引擎，将不仅仅基于关键词检索，而是能够理解Web页面的内容，并进行逻辑推理来完成复杂的查询任务，最终返回精确的结果。对语义Web和搜索引擎技术进行了简要介绍，提出一种语义搜索引擎概念模型，并对其构成模块及模块问的互操作进行了描述，最后对概念模型具体实现上的关键技术进行了简要说明。     

Scalable Web server clustering technologies

The exponential growth of the Internet, coupled with the increasing popularity of dynamically generated content on the World Wide Web, has created the need for more and faster Web servers capable of serving the over 100 million Internet users. Server clustering has emerged as a promising technique to build scalable Web servers. We examine the seminal work, early products, and a sample of contemporary commercial offerings in the field of transparent Web server clustering. We broadly classify transparent server clustering into three categories