Designing mobile computing systems using distributed objects

This article examines the application of distributed objects to the construction of highly available distributed systems for mobile, ubiquitous computing. High availability for the end user entails the provision of ubiquitous access and flexible resource-sharing. The defining characteristics of mobile computing, such as the frequent movement of users and hosts, the scarcity of network and local computing resources available to the mobile host, and the possibility of disconnections, present difficult challenges in providing high availability for clients in a distributed object system. Meeting these challenges requires dynamic object management techniques in the distributed server architecture on the fixed wired network, as well as object replica management techniques to achieve connection transparency and disconnected operation in the mobile client architecture. Various issues and solutions in constructing a dynamic distributed object-oriented architecture capable of supporting mobile computing are presented     

Upstream bandwidth optimization of thin client protocols through latency‐aware adaptive user event buffering

Thin client computing trades local processing for network bandwidth by off‐loading application logic to remote servers. User input and display updates are exchanged between client and server through a thin client protocol. In a wireless device context, it is important to achieve bandwidth efficient thin client protocols because bandwidth availability is limited and the power consumption of the wireless network interface card is directly related to the amount of data that is sent and received. This paper presents and evaluates a novel client‐based mechanism which is transparent to the server to reduce upstream bandwidth consumption. Typically, thin client protocols encode user input as a series of small packets, resulting in a major packetization overhead. By buffering user events at the thin client protocol layer, this overhead can be reduced. However, buffering strategies might result in increased response delays for the user. Therefore, models of the upstream bandwidth and the user perceived responsiveness of pull thin client protocols are presented and validated. These models are used in an adaptive framework, which determines the appropriate buffering time to minimize the bandwidth as much as possible without degrading the responsiveness. For lower network roundtrip times and users actively generating input, it is shown how bandwidth savings up to 78% can be achieved while keeping the average user perceived responsiveness below 150 ms. Copyright © 2010 John Wiley & Sons, Ltd.     

基于IMS技术的三网融合网络多媒体业务部署

提出了基于云计算架构的三网融合网络多媒体视频业务部署技术,解决了三网融合网络海量终端用户访问及多媒体业务及用户的管理等问题.给出了三网融合网络的多媒体视频业务管理模型,并且详细说明了多媒体视频应用服务器及客户端的功能模块,以实例方式说明了QoS策略决策过程.为三网融合网络多媒体业务部署提供了指导性的技术方案.     

应用RBAC技术实现MIS用户权限管理的统一

针对管理信息系统中存在的客户端应用系统和服务器端数据库系统用户权限管理不统一的问题，提出了一种应用RBAC技术的解决方案，通过对用户、角色和权限的定义和管理，结合存储过程技术，实现了前后台用户权限的统一和动态的管理。     

多线程在分布式多层管理信息系统中的应用

在分布式多层管理信息系统中,信息查询往往是用得最多的操作,查询效率的高低通常能决定整个系统的优劣。利用Delphi多线程技术,探讨了一种在客户端有效的实现远程数据存取的方法。     

Web server support for tiered services

The evolving needs of conducting commerce using the Internet requires more than just network quality of service mechanisms for differentiated services. Empirical evidence suggests that overloaded servers can have significant impact on user perceived response times. Furthermore, FIFO scheduling done by servers can eliminate any QoS improvements made by network-differentiated services. Consequently, server QoS is a key component in delivering end to end predictable, stable, and tiered services to end users. This article describes our research and results for WebQoS, an architecture for supporting server QoS. We demonstrate that through classification, admission control, and scheduling, we can support distinct performance levels for different classes of users and maintain predictable performance even when the server is subjected to a client request rate that is several times greater than the server's maximum processing rate     

Client Rendering Method for Desktop Virtualization Services

Cloud computing has recently become a significant technology trend in the IT field. Among the related technologies, desktop virtualization has been applied to various commercial applications since it provides many advantages, such as lower maintenance and operation costs and higher utilization. However, the existing solutions offer a very limited performance for 3D graphics applications. Therefore, we propose a novel method in which rendering commands are not executed at the host server but rather are delivered to the client through the network and are executed by the client's graphics device. This method prominently reduces server overhead and makes it possible to provide a stable service at low cost. The results of various experiments prove that the proposed method outperforms all existing solutions.     

基于Browser/Server模式下的通信电源远程监控

在对传统的基于客户/服务器端工作模式下的通信电源远程监控系统特点分析基础上,提出了使用浏览器作为通用客户端的监控系统,也就是通常所说的浏览器/服务器结构的网络应用.该系统易于维护和升级,操作简单.对于降低运行成本,实行状态监控起了重要的作用.     

DCOM组件在B/S系统开发中的应用

分布式计算技术在软件开发中得到了广泛的应用，它使复杂的大型网络应用程序在结构上更清晰，更易于开发。组件对象模型COM（Component ObjectModel）和分布式组件对象模型DCOM（Distributed COM）是微软软件体系结构中使用的分布式对象技术。通过分析基于COM／DCOM组件技术的分布式计算的基本原理，总结了开发使用COM／DCOM组件的基本方法和三层分布式应用程序的实现过程。最后给出了一个用DCOM组件构造的三层分布式应用系统实例。     

一种基于虚拟应用的安全防泄漏系统

针对目前日益严重的信息资产泄露问题,在对比已有的信息泄露的防御技术基础上,提出一种＂基于虚拟应用的安全防泄漏系统＂,通过集中运算、虚拟应用技术,在服务器上为每一个用户的应用构建独立的计算环境;采用远程桌面、SSLVPN技术保证集中计算环境中数据与用户操作终端的安全隔离;同时基于信息在服务器集中存储和运算,实现终端无痕（用户终端没有数据计算痕迹）,防止数据在应用过程中泄露;最后采用统一认证和应用授权发布,管理用户对数据的访问和输出控制。     

一种新的IPv6 DNS自动更新系统

本文阐述了一种新型的基于客户机/服务器模型的IPv6 DNS自动更新系统.首先分析了IPv6 DNS自动更新技术目前的进展及存在的问题,然后,针对这些问题提出了一种支持多个IPv4/v6地址、支持安全动态更新、支持地址自动检测和地址过滤、基于客户机/服务器模型的IPv6 DNS自动更新系统.此系统支持多种主流操作平台,并为用户的使用和网络的整体部署提供了极大的灵活性.最后对其以后的应用进行了展望.     

DCOM组件在B／S系统开发中的应用

分布式计算技术在软件开发中得到了广泛的应用，它使复杂的大型网络应用程序在结构上更清晰，更易于开发。组件对象模型COM（Component Obiect Model）和分布式组件对象模型DCOM（Distributed COM）是微软软件体系结构中使用的分布式对象技术。通过分析基于COM／DCOM组件技术的分布式计算的基本原理，总结了开发使用COM/DCOM组件的基本方法和三层分布式应用程序的实现过程。最后给出了一个用DCOM组件构造的三层分布式应用系统实例。     

一种面向边缘计算的可扩展网络I/O框架

作为当前的研究热点,边缘计算可以在网络边缘部署计算、存储和网络资源,为用户提供云化服务,以满足新兴应用的处理需求。但是,当前网络I/O模型的扩展性问题使得运行在边缘节点上的边缘应用难以有效地利用丰富的边缘物理资源处理海量用户的网络请求。针对边缘计算场景下网络I/O模型的数据竞争和负载不均衡问题,提出了一种新的可扩展网络I/O模型。通过试验可以看出,利用该模型的边缘应用具有良好的性能和可扩展性。     

CRSF攻击机制及防御策略研究

跨站点请求伪造（Cross—Site Request Forgery）是一种互联网上广泛存在的网络攻击,它通过第三方伪造用户请求来欺骗服务器端,达到冒充用户身份、行使用户权利的目的。文中通过分析跨站点请求伪造攻击的原理,并模拟其攻击过程、解析攻击产生的原因来向读者详细介绍此类攻击的特点,并从服务器端和客户端两个方向讨论了防御此类攻击的策略。     

Instrumentationnotes - Distributed measurement systems-A web system approach: Part I

The simplified field-system functionality testing software (FSFTS) was presented. That software was successfully used for verification of the final system functionality and the quality evaluation of its components. Then, two solutions for the server/client software for the distributed measurement system, implementing the Web as a main transmission medium, were described. The essential parts of the final system solutions are the server and the clients. The server collects remote data and makes them accessible for clients. These two solutions of the server/client system are based on a Windows operating system. The first solution implements Microsoft's .NET environment. The second one uses WAMP (Windows and free and open source software: Apache, MySQL, and PHP). The main difference between the first two solutions is how the client page is generated. The .NET case is only on the server side, and the WAMP case is on both server and client sides. Both systems produce a map/plot/ table showing the system data to the user through web browsers.     

基于网络远程实验监控系统的实现

提出了基于网络远程监控系统设计中所涉及的关键技术,采用了基于Internet远程监控实验系统,通过设计,能够接受来自网络服务器验证的远方客户端请求,并能执行远方用户的操作代理请求,允许远方用户通过动态网页查询历史数据。通过远程用户模块采用ActiveX或Java Applet嵌入到网页中的形式,实现远程用户同本地实验台信息的交互,通过与设备服务器的通信实现实验过程,实现网络服务器与动态网页之间交互实现用户的注册与登录。     

流媒体中间件在Linux下的设计与实现

在Linux平台设计了基于SIP协议的视频流媒体中间件,用来将编码服务器发送到网上的视频流数据进行集中管理,再根据用户请求的信息,将视频数据流转发给用户,避免了用户与编码服务器直接对话,极大地优化了网络资源,缓解了编码服务器的资源压力,真正意义上解决了在多路视频通信中出现网络拥塞的难题,实现了多个用户可以在任何地点、任何时间随意观看来自网络的视频信息,并在QT下设计了中间件操作界面,用户可以通过中间件来查看需要监控的用户信息,方便管理。最后在多画面客户端进行测试,达到了多路视频画面实时显示的效果。     

基于完成端口的服务器底层通信模块设计

基于Winsock的网络通信模块中，海量客户端连接请求及其数据通信的效率往往成为影响网络服务器效率的关键所在，特别是Web服务器、代理服务器、网络游戏服务器等应用，对底层通信模块性能的要求更为严格。针对实际应用，提出了一种基于完成端口的服务器底层通信模块设计方法，着重解决客户端连接量巨大、小容量数据包频繁收发等问题，在内存管理方面进行了细节优化，并实现了一个应用于实际的服务器底层通讯模块。经测试，该模块达到了项目需求提出的5000人在线的负载标准。     

基于TR069的IPTV远程升级系统的设计与实现

随着IPTV机顶盒大批量进驻用户家庭,电信运营商对机顶盒的业务变更及版本升级有了更高的需求。为了满足这一需求,本文设计了一套方案来实现对IPTV机顶盒的远程在线升级。这套方案基于TR069协议,采用Yc／S及客户端／服务器模式。在机顶盒开机时通过TR．069协议来控制流程,判断机顶盒的版本号是否需要升级。如需要升级,则发布命令使机顶盒从升级服务器上下载升级包,然后在本地完成升级。实际测试结果表明,该方案可以实现安全稳定的远程在线升级,最后总结了该方法的优点和今后进一步的研究重点。