Some users have created their own console servers using off-the-shelf commodity computer hardware, usually with multiport serial cards typically running a slimmed-down Unix-like operating system such as Linux. Such "home-grown" console servers can be less expensive, especially if built from components that have been retired in upgrades and allow greater flexibility by putting full control of the software driving the device in the hands of the administrator. This includes full access to and configurability of a wide array of security protocols and encryption standards, making it possible to create a console server that is more secure. However, this solution may have a higher TCO, less reliability and higher rack-space requirements, since most industrial console servers have the physical dimension of one rack unit (1U), whereas a desktop computer with full-size PCI cards requires at least 3U, making the home-grown solution more costly in the case of a co-located infrastructure.