VPN技術研究

電子通信論文編號:TX001         論文字數:18802,頁數:36

目錄                                           

1．引言   1
1.1 課題背景  1
1.2 VPN的特點  1
2.1 隧道技術   2
2.2點對點隧道協議PPTP（Point-to-Point Tunneling Protocol）   2
2.2.1 建立控制連接   3
2.2.2 PPP協議   3
2.2.3 PPTP數據封裝   6
2.3 SSL（安全套接協議）   8
2.3.1 SSL的體系結構   8
2.3.2 SSL握手過程步驟  9
2.3.3對稱加密和非對稱加密   10
2.4 IPSec(Internet 協議安全)   10
2.4.1 IPSec的工作原理   10
2.4.2 SA（Security Association）安全關聯   11
2.4.3 AH（Authentication Header）認證頭   11
2.4.4 ESP（Encapsulating Security Paylod）封裝安全負載   12
2.4.5 IKE協議   13
3．VPN的實現   14
3.1 PPTP VPN的實現  14
3.1.1配置服務器   15
3.1.2 WINXP下客戶端的配置   16
3.1.3 建立連接   17
3.2 SSL VPN的實現  18
3.2.1 openvpn安裝  18
3.2.2 配置VPN Server   19
3.2.3 安裝和配置WINDOWS XP下的客戶端   21
3.3 IPSec VPN的實現   22
3.3.1編譯內核（需要截圖）   22
3.3.2 安裝OpenSWan   24
3.3.3 配置OpenSWan   25
4.1 幾種VPN的特點   28
4.2 幾種VPN的比較   29
4.3 結論   30
參考文獻   30
致    謝    32

摘要
隨著全球經濟的發展，無論是大企業還是中小企業，都在各地擁有自己的分支機構。 VPN技術以其管理簡單,費用低廉的優點成為企業構建內部廣域網絡的首選。VPN服務市場在2005年取得了總銷售額230億美元的驕人業績，預計到2009年還將增長22%，前景非常廣闊。
VPN(虛擬專用網)不是真的專用網絡，但它卻能夠通過公用網絡實現專用網絡的功能，能為企業的商業運作提供一個可靠、安全的數據傳輸網絡。實現VPN技術的方式很多，本文以在Linux系統下常用的三種軟件VPN：PPTP VPN ，SSL VPN 和IPSEC VPN為例，對各種VPN的工作原理做了詳細的闡述，并對實現這些VPN的功能，需要在其服務器端和客戶端如何配置做出了詳細的總結。
在最后階段對幾種VPN進行比較，得出結論：IPSec VPN適合擁有較多的分支機構，維護成本較高，IT建設、管理和維護方面擁有一定經驗的員工的大中型企業。而SSL VPN適用于那些需要很強靈活性的企業，員工需要在不同地點都可以輕易的訪問公司內部資源，并可能通過各種移動終端或設備隨時進行訪問，企業的IT維護較低。相對而言，PPTP配置簡單方便，適合那些規模較小，對安全要求較低的小企業。
Study of the VPN Technology

Abstract
Along with the development of global economy, regardless of the big enterprises or mid- and small-scale enterprises, all have their own branches in each place. The VPN technology, for its merits of simple management and the low expense, becomes the first choice of the enterprise to construct the internal wide area network (WAN). In 2005, the VPN service market has obtained excellent achievements with the total sales volume of 23 billion US dollars, which is surprising, it is estimated that it will increase by 22% in 2009, the prospect is extremely broad.
The VPN (Virtual Private Network) technology is not the real private network, but it can realizes the function of private network through the public network to offer a kind of reliable and safe data transmission network for enterprise's commercial operation. Taking three VPN software often used under Linux system such as PPTP VPN, SSL VPN, and IPSEC VPN as example, this article makes elaboration to each kind of VPNs’ principle of work, and summarizes in details its function how to configure in its server end and client end
In the end of the article, I carry on the comparison to several kinds of VPN, and then reach the conclusion, that is, IPSec VPN is suitable for large and middle-scale with more branches and higher maintenance cost, the IT construction, the management and the enterprises. Because their staff have the certain experience in the aspect of maintenance. But SSL VPN is suitable for the enterprises which need very strong flexibility and cost little on IT, there the staff need in different places to be allowed to easily visit interior resources of the company, and are able to carry on the visiting as necessary through each kind of mobile termination or the equipment. Relatively, as PPTP VPN can be configured simply and conveniently, it suits these small businesses with low safety requisition.