SSL VPN or Secure Sockets Layer Virtual Private Network is a form of VPN that can be used with a standard web browser. Unlike IPSec VPN, it does not require the installation of specialized client software on an end user’s computer. SSL VPN consists of one or more VPN devices to which the end-user can connect securely through a standard web browser.

IPSec is integrated with the IP layer of the OSI protocol stack. But SSL VPN uses the Secure Sockets Layer (What is Secure Sockets Layer ?) for authentication and encryption. It uses a standard web browser to communicate with the VPN devices. And the traffic between the web browser and the SSL VPN device is encrypted with the SSL protocol or its successor, the TLS protocol (How is TLS different from SSL ?).

What is an SSL VPN?

There are mainly two types of SSL VPN :

• SSL Portal VPN
• SSL Tunnel VPN

SSL Portal VPN – In this type of SSL VPN, the end-user connects to a single website called a portal. And from the portal, the user accesses multiple network services. The end-user first accesses the SSL VPN gateway and authenticates herself using a standard authentication method supported by the gateway. She is then redirected to the portal’s web page, through which she can connect to other network services.

SSL Tunnel VPN – In this type of SSL VPN, the end-user can securely connect to multiple network services through a tunnel that runs under SSL. SSL Tunnel VPNs enable an user to access more functionalities that are not accessible to SSL Portal VPNs.