Ethernet over Twisted-Pair Cabling

Ethernet technology standards are the responsibility of the IEEE 802.3 working group. This group is responsible for evaluating and eventually approving Ethernet specifications as new Ethernet technologies are developed such as Gigabit and 10Gigabit Ethernet. Although this group defines the standards for Ethernet, it looks to other established standards organizations to define the specifications for physical cabling and connectors. These organizations include the American National Standards Institute (ANSI), Engineering Industry Association (EIA), and Telecommunications Industry Association (TIA). The TIA/EIA published specifications for twisted-pair cabling are found in the TIA/EIA-568-B specification document.

The more common forms of cabling are unshielded twisted-pair (UTP) and optical fiber. Twisted pair cable comes in a variety of forms. The most common categories in today's networks are the following:

• Category 3

• Category 5

• Category 5E

• Category 6

The categories represent the certification of the radio frequency capability of the cabling.

Category 3 was initially designed as voice grade cable and is capable of handling transmissions using up to 16 MHz. Category 5 is capable of handling transmissions up to 100 MHz. Category 5E is an improved version of Category 5; while still limited to 100 MHz, Category 5E defines performance parameters sufficient to support 1000BASE-T operation.

Category 6 provides the best possible performance specification for UTP cabling. Category 6 specifies much stricter requirements for cabling than Category 5 and 5E. The frequency range of Category 6 extends to 250 MHz, in contrast to Category 5 and 5E's 100 MHz. While new cabling installations typically install Category 5E or 6 cabling, Category 5 cabling can be utilized for 1000BASE-T applications. With few exceptions, if 100 Mbps Ethernet is operating without issues up to 100 meters on a Category 5 cable plant, 1000BASE-T will operate as well.

Although 10 Mbps and 100 Mbps Ethernet often use two pairs (pins 1, 2, 3, and 6) of twisted-pair cabling, Gigabit Ethernet over twisted pair uses all four pairs of wiring in the twisted-pair cable.

Even if the actual twisted pair is rated a specific category, it does not imply that a cabling infrastructure properly supports the category specification end-to-end. Installation and accessories (such as patch panels and wall plates) must meet the standard as well. Cable plants should be certified from end-to-end. When installing a cabling infrastructure, the installer should be able to use specialized equipment to verify the specifications of the cabling system from end-to-end