Network Cabling and Components

Stephen Bucaro

Although the power and sophistication of networking protocols and software is impressive, a network could not operate without physical cable and components. Even a wireless network needs physical components such as access points. And because wireless networks are subject to problems like interference and lower security, cable will be the media of choice for many networks for a long time to come.

Coaxial Cable

Coaxial Cable (coax) uses a solid wire in its core that is surrounded by a braided metal shield. Insulating material separates the wire core and metal shield. The central wire carries the electrical signal of the network data. The metal shield protects the data from electrical interference. Early Ethernet networks used thick RG-8 coaxial cable. This cable is referred to as Thicknet.

The IEEE created a system to specify network cabling. Thicknet is designated 10base5. The 10 specifies the maximum speed in megabits per second at which the cable can transfer data. “Base“ stands for baseband signal type. Baseband means it uses a digital signal. The 5 specifies that 500 meters the maximum length of a cable segment.

Thicknet cable is very rigid, so the network computers and peripherals do not connect directly to the cable. Each computer or other device, referred to as a node, connects to the coax using a thinner drop cable. The Thicknet backbone may run in the ceiling, with drop cables used to attach the individual computers. Each drop cable is connected to the Thicknet backbone using a transceiver.

To attach a transceiver to the Thicknet cable requires a technician to cut a hole through the cable shield and attach a “vampire tap“ which pierces the wire core of the coaxial cable. The transceiver is then connected to the network interface card of the computer using a cable with a DB-15 connecter called a DIX (Digital Intel Xerox) or AUI (Attachment Unit Interface).