An SSL VPN is a type of virtual private network that uses the Secure Sockets Layer protocol -- or, more often, its successor, the Transport Layer Security (TLS) protocol -- in standard web browsers to provide secure, remote-access VPN capability. SSL VPN enables devices with an internet connection to establish a secure remote-access VPN connection with a web browser. An SSL VPN connection uses end-to-end encryption (E2EE) to protect data transmitted between the endpoint device client software and the SSL VPN server through which the client connects securely to the internet.
SSL VPNs rely on the TLS protocol, which has replaced the older SSL protocol, to secure remote access. SSL VPNs enable authenticated users to establish secure connections to internal HTTP and HTTPS services via standard web browsers or client applications that enable direct access to networks.
There are two primary types of SSL VPNs: VPN portal and VPN tunnel. An SSL portal VPN enables one SSL VPN connection at a time to remote websites. Remote users access the SSL VPN gateway with their web browser after they have been authenticated through a method supported by the gateway. Access is gained via a webpage that acts as a portal to other services.
An SSL tunnel VPN enables users to securely access multiple network services via standard web browsers, as well as other protocols and applications that are not web-based. The VPN tunnel is a circuit established between the remote user and the VPN server; the server can connect to one or more remote websites, network services or resources at a time on behalf of the client. The SSL tunnel VPN requires the web browser to handle active content and provide functionality that is not otherwise accessible through an SSL portal VPN.