The modular structure of OpenVPN can not only be found in its security model, but also in the networking scheme. James Yonan chose the Universal TUN/TAP driver for the networking layer of OpenVPN.

The TUN/TAP driver is an open-source project that is included in all modern Linux/UNIX distributions as well as Windows and Mac OS X. Like SSL/TLS it is used in many projects, and therefore it is steadily being improved and new features are being added. Using the TUN/TAP devices takes away a lot of complexity from OpenVPN's structure. Its simple structure brings increased security compared to other VPN solutions. Complexity is always the main enemy of security. For example, IPsec has a complex structure with complex modifications in the kernel and the IP stack, thereby creating many possible security loopholes.

The Universal TUN/TAP driver was developed to provide Linux kernel support for tunneling IP traffic. It is a virtual network interface, which appears as authentic...