The OpenVPN security model is based on SSL, the industry standard for secure communications via the internet. OpenVPN implements OSI layer 2 or 3 secure network extension using the SSL/TLS protocol.
OpenVPN has been ported to various platforms, including Linux and Windows, and its configuration is likewise on each of these systems, so it makes it easier to support and maintain. OpenVPN can run over User Datagram Protocol (UDP) or Transmission Control Protocol (TCP) transports, multiplexing created SSL tunnels on a single TCP/UDP port. OpenVPN is one of the few VPN protocols that can make use of a proxy, which might be handy sometimes.