Media

An important part of designing and installing an Ethernet is selecting the appropriate Ethernet medium. There are four major types of media in use today: Thickwire for 10BASE5 networks, thin coax for 10BASE2 networks, unshielded twisted pair (UTP) for 10BASE-T networks and fiber optic for 10BASE-FL or Fiber-Optic Inter-Repeater Link (FOIRL) networks.

This wide variety of media reflects the evolution of Ethernet and also points to the technology's flexibility. Thickwire was one of the first cabling systems used in Ethernet but was expensive and difficult to use. This evolved to thin coax, which is easier to work with and less expensive.

The most popular wiring schemes are 10BASE-T and 100BASE-TX, which use unshielded twisted pair (UTP) cable. This is similar to telephone cable and comes in a variety of grades, with each higher grade offering better performance.

Level 5 cable is the highest, most expensive grade, offering support for transmission rates of up to 100 Mbps. Level 4 and level 3 cable are less expensive, but cannot support the same data throughput speeds; level 4 cable can support speeds of up to 20 Mbps; level 3 up to 16 Mbps.

The 100BASE-T4 standard allows for support of 100 Mbps Ethernet over level 3 cable, but at the expense of adding another pair of wires (4 pair instead of the 2 pair used for 10BASE-T); for most users, this is an awkward scheme and therefore 100BASE-T4 has seen little popularity. Level 2 and level 1 cables are not used in the design of 10BASE-T networks.

For specialized applications, fiber-optic, or 10BASE-FL, Ethernet segments are popular. Fiber-optic cable is more expensive, but it is invaluable for situations where electronic emissions and environmental hazards are a concern.

Fiber-optic cable is often used in interbuilding applications to insulate networking equipment from electrical damage caused by lightning. Because it does not conduct electricity, fiber-optic cable can also be useful in areas where large amounts of electromagnetic interference are present, such as on a factory floor.

The Ethernet standard allows for fiber-optic cable segments up to 2 kilometers long, making fiber optic Ethernet perfect for connecting nodes and buildings that are otherwise not reachable with copper media.