Bus Topology

Bus Topology
In a bus topology, all computers are attached to a single continuous cable that is terminated at both ends, which is the simplest way to create a physical network. Originally, computers were attached to the cable with wire taps. This did not prove practical, so drop cables were used to

attach computers to the main cable. In 10Base-2 Ethernet, no drop cables are used, but instead, a “T” is inserted in the main cable wherever a station needs to connect. Figure 1.5 shows an example of a bus network. Notice how the cable runs from computer to computer with several bends and twists.

Example:

An example of a physical bus topology

     When communicating on a network that uses a bus topology, all computers see the data on the wire. This does not create chaos, though, because the only computer that actually accepts the data

is the one to which it is addressed. You can think of a bus network as a small party. David is already there, along with 10 other people. David would like to tell Joe something. David yells out, “Joe! Will

you grab me a cup of coffee, please?” Everyone in the party can hear David, but only Joe will respond. A star network with a hub, which you’ll read about later, also operates in this manner.

As with most things, there are pros and cons to a bus topology. On the pro side, a bus

 topology has the following characteristics:

•  Is simple to install
• Is relatively inexpensive
• Uses less cable than other topologies

The following characteristics describe the con side of a bus topology:

• Is difficult to move and change
• Has little fault tolerance

 (a single fault can bring down the entire network)

• Is difficult to troubleshoot