利用L2TP构建安全的VPN

对于构建VPN 来说，网络隧道(Tunneling)技术是个关键技术。网络隧道技术指的是利用一种网络协议来传输另一种网络协议，也就是将现有的透明网络信息进行再次封装，从而保证网络信息传输的安全性。它主要利用网络隧道协议来实现这种功能，具体包括二层隧道协议（用于传输二层网络协议）和三层隧道协议（用于传输三层网络协议）。二层隧道协议L2TP（Layer 2Tunneling Protocol）是一种基于点对点协议PPP的二层隧道协议。在由L2TP构建的VPN中，有两种类型的服务器，一种是L2TP 访问集中器LAC（L2TPAccess Concentrator ），它是附…     

华为VPN解决方案

华为推出的Quidway系列通信产品支持多种VPN技术。在QuidwayA8010接入服务器中,支持二层隧道协议LZTP及PPTP。在Quidway系列路由器中,提供对上述VPN协议的支持;包括：（1）支持作为LAC及LNS,一台路由器可以同时作为一个L2TP隧道连接的发起方和另一个L2TP隧道连接的接收方,支持预协商等L2TP协议的特性,支持多个备份LNS。华为的路由器对于L2TP协议专门提供了一种方法,能够利用L2TP实现局域网与局域网之间的互联。（2）华为路由器的三层协议支持IPX、IP,则可以利用GRE实现IPinIP以及IPXoverIP。（3）实现IPSe…     

VPN网络隧道技术的研究

本详细介绍了VPN网络隧道技术和目前主要的隧道协议L2TP和IPSec的原理和技术特点，并简要介绍通过网络隧道技术建立VPN网络。     

基于4G LTE网络的集团客户VPDN业务探讨

本文从VPDN业务接入的关键技术入手,介绍L2TP隧道协议和L2TP OVER IPSEC VPN协议。结合集团客户业务安全性要求,在4G现有网络资源且不增加核心网设备的基础上,提出利用L2TP OVER IPSEC VPN进行集团客户VPDN业务的接入方案,并对网络连通性、IPSEC加解密功能以及视频监控、上传下载业务组织了实践测试,通过测试验证该方案是可行的。     

计算机在电子学方面的应用

TP39,TP391.7 2003051776VPN在远程教育中的应用/肖玲(湖南大学)份计算技术与自动化.一2003,22(1)一61一64文中介绍了VPN的概念、分类和VPN的隧道技术,提出了利用远程拨号接入V PN技术来对异地、分散的远程教育用户实现异步式教学模式,并对此模型的实现和性能进行了分析.图3参5(木)针对现有静态网络安全模型存在的问题,提出了一种动态网络安全框架模型.该安全模型利用各种安全组件构建了立体的五层防御体系,并实现了防御能力的动态升级.图3参4(木)TP39 20D3051777计算机无线网络组网技术及应用/曹卫京11计算技术与自动化一2 003,22(…     

基于L2TP的VPN服务器程序设计

虚拟私有网络VPN(VirtualPrivateNetwork)是近年来兴起的网络热门技术。分析了VPN中的关键技术L2TP协议的工作原理,并在Linux上根据RFC2661实现了L2TP协议中关键的部分:LNS服务器。通过对这些问题的描述,使得Windows的客户端能够通过简单的拨号连接访问LNS服务器,用最简单廉价的方式,高效实用地部署企业的VPN。     

特定应用需求下VPN的隧道协议选择

为了实现安全通信,越来越多的机构使用VPN隧道这种相对廉价和便捷的方法来创建私有网络。VPN协议分为点到点和远程访问两种类型,在安全机制方面表现出不同的特性集。但是没有基于机构特定应用需求的VPN。文章分析了不同的VPN隧道协议,如GRE、IPSec、PPTP和L2TP with IPSec的吞吐量,往返时间,抖动和安全参数等方面的性能。结果表明,GRE更适合于对延时和带宽敏感的点到点VPN环境中,而L2TP比PPTP更适用于远程接入VPN。     

基于二层VPN技术浅谈

VPN的具体实现是采用隧道技术将企业网的数据封装在隧道中进行传输。隧道协议可分为第二层隧道协议PPTQ、L2F、L2TP和第三层隧道协议GRE，IPSse，它们的本质区别在于用户的数据包是被封装咱哪种数据包中在隧道中传输。     

VPN隧道协议发展现状

本文首先介绍了VPN常见的隧道协议,然后对三层隧道协议和二层隧道协议进行了分析比较,剖析了目前广泛使用的L2TP协议存在的问题,最后就这几种隧道协议的成熟程度进行了小结,并对企业和运营商目前如何组建VPN提出了自己的看法。     

VPN隧道协议发展现状

本首先介绍了VPN常见的隧道协议,然后对三层隧道协议和二层隧道协议进行了分析比较,剖析了目前广泛使用的L2TP协议存在的问题,最后就这几种隧道协议的成熟程度进行了小结,并对企业和运营商目前如何组建VPN提出了自己的看法。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks