基于IPSec和L2TP隧道实现技术的研究

对于构建VPN系统来说，网络隧道(Tunnelling)协议是关键技术。当前隧道协议主要有两种：链路层隧道协议和网络层隧道协议。从安全的角度分析，链路层隧道提供的主要安全功能是基于用户和连接的认证，而网络层隧道还提供了数据加密的功能。要提供一个完整的VPN，即一方面该VPN支持点对点接入，提供多协议封装；另一方面需要提供包括认证和加密的功能。所以，L2TP协议和IPSec协议的结合使用成为研究和实现的热点，本文研究和探讨了基于IPSec协议和L2TP协议隧道的原理，并且提出了基于L2TP和IPSec结合使用的实现。     

基于L2TP无线局域网安全解决方案

为了使读者更加了解无线局域网L2TP隧道认证机制的工作原理,在无线局域网环境中部署L2TP的,方法是：LAC（L2TP访问集中器L2TP Access Concentrator）放置在与无线网络连接的PC上,LNS（L2TP网络服务器L2TP Network Server）放置在有线内部网内,用户则需要自己建立L2TP通道,同时也介绍了L2TP隧道认证在实际的运行环境中的运行情况,根据实验详细分析了L2TP认证机制原理,最后提出了基于L2TP协议的无线局域网安全解决方案。     

基于证书的L2TP-VPN在校园网的应用

摘要：L2TP—VPN通过使用PPP协议建立第二层隧道,将第二层数据封装在IP分组内部进行传输,并通过数字证书进行身份认证,从而提供了一种个人和校园网安全连接的方案,可以实现远程接入、资源共享和网络管理等多种服务。     

基于Kerberos认证的虚拟专用拨号网络研究

本文介绍了实现VPDN常用的第二层隧道协议(L2TP)以及基于L2TP的VPDN中的用户认证过程,分析了Kerberos认证协议和基于Kerberos认证的VPDN的实现。     

L2TP下可信的VPN方案设计与实现

提出了一个用CA+对称L2TP路由器的模型，该模型身份认证和密钥由数字证书来完成，而加密和数据完整性认证则由L2TP路由器完成。和现有LAC+LNS的接入方案比较，该方案明确和简化了工作内容，并且解决了L2TP隧道内多路呼叫独立安全的问题。L2TP路由器在考虑了Linux内核的特点后，进行架构的设计来完成数据的处理。试验表明该方案兼顾了安全和性能，提供了一个高速可信的VPN解决办法。     

Windows 2000中实现VPN隧道协议的研究与比较

在Windows2000中，提供了两种隧道协议，可以让我们方便的创建虚拟专用网：PPTP（点对点隧道协议）和附带IPSec（网际协议安全）的L2TP（第二层隧道协议）。本文阐述了PPTP与L2TP／IPSec实现远程接入VPN的比较。     

VPN安全管理技术

VPN技术具有较高的安全性并且实现较简单,费用低廉。本文阐述了VPN中采用的隧道技术,加解密技术,身份认证,使用者与设备身份认证技术等安全技术的实现,着重介绍了VPN中应用的第2层隧道协议、第3层隧道协议及SSL等协议,分析了SSLVPN技术的主要优点及其不足之处。简单介绍了现行的SKIP与ISAKMP／OAKLEY密钥管理技术和常用的身份认证技术。     

SSL VPN的相关介绍与安全性研究

随着因特网的快速发展,近几年不断出现了一些新的网络协议,包括点对点隧道协议(PPTP)、第2层隧道协议(L2TP)、安全IP(IPSec)协议等。其中PPTP协议允许对IP,IPX或NetBEUI数据流进行加密,然后封装在IP包头中通过企业IP网络或公共互联网络发送;L2TP协议允许对IP,IPX或NetBEUI数据流进行加密,然后通过支持点对点数据报传递的任意网络发送,如IP,X.25,帧中继或ATM;IPSec协议允许对IP负载数据进行加密,然后封装在IP包头中通过企业IP网络或公共IP互联网络如Internet发送。VPN利用各种安全协议,在公众网络中建立安全隧道,提供专用网络的功能和作用。本文总结了SSLVPN的基本原理,研究了SSLVPN的安全性,并与IPSecVPN做了相关比较。     

集成L2TP和IPSec技术构建安全的远程接入虚拟专用网

目前远程接入VPN主要基于L2TP协议实现，但是L2TP隧道传输协议本身没有为通信提供任何形式的安全保护，因此这种结构的VPN存在着安全隐患：为了解决这个问题，在研究远程接入VPN特点和功能基础上，利用IPSec协议为L2TP协议提供安全保护，提出了集成L2TP和IPSec构建安全的远程接入VPN方案。     

基于IPSec和L2TP的访问型VPN解决方案研究

隧道技术是构建虚拟专用网(VPN)的关键技术。该文介绍了两种主要的的隧道协议L2TP和IPSec,分析了基于L2TP构建访问型VPN的安全隐患和制约IPSec构建IP VPN的原因,提出了基于L2TP和IPSec结合使用的访问型VPN的解决方案。     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

基于QTE的蒙古文显示机制研究与实现

蒙古语言是中国蒙古族使用的通用语言,由于蒙古文区别于其他文字的书写方式和其自身变形机制等特点,在很多通用的文字处理引擎中都不被支持。在嵌入式产品开发与应用领域中Linux加QTE已经成为流行方式。该文给出了一种在QTE环境上实现基于标准Unicode的蒙古文点阵显示和变形算法, 并自定义了支持蒙古文的QTE组件,扩展了QTE功能,为在Linux加QTE方式的嵌入式体系结构中处理蒙古文提供了一种解决方法。