Thick Ethernet, officially known as 10 Base 5, is the oldest form of Ethernet. It was originally developed in the late 1970's by Digital Equipment Corporation, IBM, and Xerox, and became an international standard (IEEE 802.3) in 1983.
10 Base 5 is laid out in a bus topology, with a single coaxial cable connecting all nodes together. At each end of the coaxial cable is a terminator. Each node on the network physically connects to the coaxial cable through a device called a transciever and an AUI cable is connected between the node and the transciever. Figure One shows a simple 10 Base 5 network.
Thick Ethernet Physical Topology
The cable type used for 10 Base 5 networks is a specialized form of RG-8 coaxial cable. This cable consists of a single central wire surrounded by a plastic insulation, which is in turn surrounded by four shields and an outside jacket. The resulting cable is nearly 1/2 inch in outside diameter, and is relatively heavy and inflexible. However, it is very resistant to external interferance.
A single 10 Base 5 segment may be up to 500 meters (1650 feet) in length and may have up to 255 nodes connected to it. Please note that each node must be at least 2.5 meters (8.25 feet) apart.
As with any technology, there are pros and cons to 10 Base 5 which make it very useful in some applications and not a good choice for others. Below are some of the characteristics of the technology:
Due to the inherent disadvantages in the design of 10 Base 5, it is not commonly chosen as a technology for the bulk of today's Ethernet networks. However, it is very useful in specialized applications which take advantage of its strengths but avoid the technology's weaknesses.
Today, the most common use for 10 Base 5 is as a "backbone" technology. Basically, a backbone is used to connect together multiple 10 Base-T hubs to create one large network, as depicted in Figure Two. Another common use is for connecting several distant devices to a central network.
Thick Ethernet Backbone
10 Base 5 is a good choice for networks which do not require much change after the initial installation is completed, and which will have only a limited number of devices attached directly to the coaxial cable.