Ethernet over UTP (10BT/802.3i)

One form of cabling supported by Ethernet is low Unshielded Twisted Pair (UTP) cable.

UTP Cabling

This type of cable is very cheap to purchase and is flexible and easy to install. It is also used by other networking systems than Ethernet and may for instance be used to provide telephone lines to offices. The common of UTP cabling for many purpose eases installation and management of the cabling. Some types of twisted pair cables can be used for communications up to 10 Gbps.

A typical example of the use of 10BT wiring to connect computers back to a central hub

The UTP cabling system uses a RJ-45 connector and 100 Ohm unshielded twisted pair cabling. This connects the computer directly (i.e. using a point to point link) to a wiring hub which acts as a media repeater. The maximum distance of a UTP link is 100 m. It is normally used to connect work groups of users, sometimes by wiring an entire floor with outlets to each work area. The diagram below shows the UTP cable (with an RJ-45 connector plug) and the socket for the cable on a network interface card in a computer. The cable forms a point-to-point connection between the computer and a hub/switch.

Connection of transceiver on equipment to a 10BT Ethernet network

10 BT Networks

The use of UTP for Ethernet at 10 Mbps is known as 10 BasebandT (10BT), indicating that it is specified for baseband communications (i.e. not modulated) at 10 Mbps using twisted pair cabling.

The other end of a cable is connected to a 10BT hub. (Sometimes a patch panel is used to make wiring easy, this simply provides a direct electrical connection between two cable segments). The hub is a repeater with a number of 10BT ports. Some hubs (e.g. the one shown below) also have an Transceiver AUI port or 10B2 port to also allow connection to other media.

An 8 port 10BT Hub with an AUI/10B2 port for connection to a fibre/coaxial cable network. Each of the 8 ports has an RJ-45 connector for connection to the twisted pair cable segment (top). An indicator light (bottom) shows when a cable is connected and when data is being sent from equipment connected to each of the cables.

Faster Ethernet Networks using UTP

An installed UTP Category 5 cabling system may be used to support Fast Ethernet by simply changing the equipment installed at both ends of the cable. The enhanced specification of Cateogory 5e (a common standard for installation) also supports Gigabit Ethernet. A higher specification of cable, Category 6, is required for 10 Gigabit Ethernet.

Summary

A summary of the properties of this type of cabling is given below:

Segment length 0.6m – 100 m
Cable flexible and very cheap
Standard RJ-45 connector used (also can be used for telephone and other networks)
Integrated or external transceiver (often built-in to equipment)
Requires a hub/switch to connect to the LANEasy to manage (also can be used for telephone and other networks).
Easy to upgrade (100BT and 1000BT will support this media)

For more information see:

Information about Unshielded Twisted Pair (UTP) cabling

Operation of a hub

Information about LAN equipment including 10BT Hubs

Fast Ethernet over UTP

Gigabit Ethernet over UTP

Gorry Fairhurst - Date: 01/03/2007 EG3567