OpenVPN

"OpenVPN is a full-featured SSL VPN solution"
The OpenVPN application was designed to be a full-featured SSL VPN solution which can accomodate a wide range of configurations, including remote access, site-to-site VPNs, WiFi security, and enterprise-scale remote access solutions with load balancing.

OpenVPN implements OSI layer 2 or 3 secure network extension using the industry standard SSL/TLS protocol, supports flexible client authentication methods based on certificates, smart cards, and/or 2-factor authentication, and allows user or group-specific access control policies using firewall rules applied to the VPN virtual interface. OpenVPN is not a web application proxy and does not operate through a web browser.

Here are some key features of "OpenVPN":

· tunnel any IP subnetwork or virtual ethernet adapter over a single UDP or TCP port,
· configure a scalable, load-balanced VPN server farm using one or more machines which can handle thousands of dynamic connections from incoming VPN clients,
· use all of the encryption, authentication, and certification features of the OpenSSL library to protect your private network traffic as it transits the internet,
· use any cipher, key size, or HMAC digest (for datagram integrity checking) supported by the OpenSSL library,
· choose between static-key based conventional encryption or certificate-based public key encryption,
· use static, pre-shared keys or TLS-based dynamic key exchange,
· use real-time adaptive link compression and traffic-shaping to manage link bandwidth utilization,
· tunnel networks whose public endpoints are dynamic such as DHCP or dial-in clients,
· tunnel networks through connection-oriented stateful firewalls without having to use explicit firewall rules,
· tunnel networks over NAT,
· create secure ethernet bridges using virtual tap devices, and
· control OpenVPN using a GUI