本文中我們提出一種新的SSL VPN 體系結構，以支持所有應用，同時增強抵抗Dos 和分類的Dos 攻擊的能力。SSL VPN 的關鍵優勢是不需要特定的客戶端軟件。當用戶要求訪問一個服務器時，由Java Applet 編寫的SSL 客戶端模塊首先被下載到主機上。但是，
并不所有應用都可以很好運行的，因為客戶不能通過HTTPS 連接某些我們熟知的應用。而且，當SSL 端口受到Dos 或分類的Dos 攻擊時，我們不能使用VPN 進行連接。改進的VPN同樣使用現存SSL VPN 中應用的Java Applet，但是這Applet 實現的功能我們稱之為動態編碼，它通過Java 遠程方法調用（RMI）實現動態改變。VPN 客戶端Applet 可以和服務器端的VPN 服務器和防火墻進行互操作。
關鍵字：SSL VPN 動態編碼 Java Applet RMI

Abstract：In this paper, we propose a port randomized VPN architecture such that any
application can use the VPN and the VPN has strength against DOS or DDOS. A key advantage of SSL VPN is that no specialized client software is required. When a user requests access to a server, the SSL client module, which is a Java Applet code, is downloaded into the host at first. However, it is quite likely that with a server through an HTTPS tunnel in some applications as we know. Moreover, there is the possibility that we can not use the VPN connections when the SSL port is under DOS or Distributed DOS(DDOS) attack. The proposed VPN use the same Java Applet as existing SSL VPNs use , but the function of the applet, which we call mobile code, is dynamically changed by Java Remote Method Invocation(RMI).The VPN client applet can cooperate with a VPN server and a firewall in server side.
KeyWords: SSL VPN , mobile code, Java Applet， RMI