A full-featured SSL/TLS based VPN solution.
OpenVPN is a full-featured open source SSL/TLS VPN solution that
accommodates a wide range of configurations and authentication models.
Starting with the fundamental premise that complexity is the enemy of
security, OpenVPN offers a cost-effective, lightweight alternative to
other VPN technologies that is well-adapted for small companies and
organizations.
The OpenVPN security model is based on SSL/TLS, the industry standard
for secure communications over the internet. OpenVPN implements OSI
layer 2 or 3 secure network extension using the SSL/TLS protocol,
supports flexible client authentication methods based on certificates,
smart cards, and/or 2-factor authentication.
Due to the continuous research of higher performance, OpenVPN is being
extended with kernel acceleration on a number of platforms. The idea is
to keep the fast path (the data channel) in kernelspace and thus
eliminate any overhead brought by the userspace processing. This
solution is called DCO: Data Channel Offload.