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VPN (Virtual Private Network) is the last few years a new network Liaison concept. It is the rapid development of Internet, the growing economic globalization, information and network security issues have become increasingly prominent this three common factors of product. Research, VPN solutions to China's information network security, and security is extremely important practical value. Virtual Private Network is a network of Internet technology and communications needs of the rapid development of the product. Along with the Internet's rapid technology development and its application to the continuous promotion of the area, many sectors (such as government, finance, the military, Enterprise Group, etc.) more and more aware of the communal use of cheap telecommunications facilities constructed their own VPN importance VPN conducted by the departments of safety data transmission, thus pushing forward the VPN in theoretical research and technological development achieved. We first give a definition of VPN, functions and advantages; VPN application classification and the classification of the environment; Comparison of several key for VPN security advantages and disadvantages of the agreement, and a detailed explanation of PPTP and L2TP, IPSEC foundation of the agreement. This paper proceeded to the key VPN technology to do in-depth research, and focuses on the tunnel technology, MPLS technology, security technology. Finally a detailed overview of VPN in the actual application and realization of the case. This study not only solve the network security related issues, for business users to use the Internet formed a private network integrity solutions, and related technology products has completed its work successfully applied to the client network environment. very practical, and value.

The hypothesized special-purpose net is a new network concept whichproposed in recent years. It is the Internet rapid development, thesocial economy day by day globalization, the information and thenetwork security question highlights the product day by day whichthese three aspects factor affects together. The research, realizesthe VPN solution, has the extremely important practical value to ourcountry network security and the information security. The hypothesized special-purpose net is the network interconnectiontechnology and the correspondence demand swift and violent developmentproduct. Along with the Internet technology fast development and itsthe application domain unceasing promotion, many professionsdepartments (for example government, finance, army, enterprise groupand so on) more and more realized constructs own VPN to the useinexpensive public foundation correspondence facility the importance,carries on this department data through VPN the safe transmission,thus impelled VPN in the fundamental research and the realizationtechnology development. This article has first produced the VPN definition, the function andthe merit; VPN classification and each classified suitable applicationenvironment; Compared several kinds to use in with emphasis to realizethe VPN security agreement good and bad points, and in detailelaborated PPTP and the L2TP agreement, the IPSEC agreementfoundation. This article met has been doing the thorough research toVPN each essential technology, and elaborated the tunnel technologywith emphasis, the MPLS technology, the security technology. Finallyin detail outlines VPN in the practical application case and therealization. This article research not only has solved the network security relatedproblem, provided one kind for the enterprise user to set up theprivate network using Internet the integrity solution, moreover thecorrelation technology already completed the product work, the successapplies in the actual customer network environment, had the verystrong usability and the promoted value.