When mainframe and minicomputer systems were the primary computing systems, data centers used proprietary cabling that was typically installed directly between equipment. See Figure 14.1 for an example of a computer room with unstructured nonstandard cabling designed primarily for mainframe computing.
With unstructured cabling built around nonstandard cables, cables are installed directly between the two pieces of equipment that need to be connected. Once the equipment is replaced, the cable is no longer useful and should be removed. Although removal of abandoned cables is a code requirement, it is common to find abandoned cables in computer rooms.
As can be seen in the figure, the cabling system is disorganized. Because of this lack of organization and the wide variety of nonstandard cable types, such cabling is typically difficult to troubleshoot and maintain.
Figure 14.2 is an example of the same computer room redesigned using structured standards-based cabling.