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Module 3
Lesson 4
Linear bus topology

Objective
Illustrate the characteristics of the linear bus topology.

Now that you know how topologies can affect networks, it's time to learn more about the different types of typologies. The term "linear" refers to a line, and the linear bus is a network configuration in which each computer is connected to the next in a (more or less) straight line. A small bus network is shown in the graphic below.

linear bus network

One important characteristic of the linear bus is that it has a beginning and an end. When computers are cabled in a line, the signal travels down the cable. When it reaches the end, it can "bounce" back (this is called signal bounce), interfering with network communications. To prevent this, a bus network must be terminated; that is, small devices called terminators are placed at both ends of the bus.
 


TIP:In addition to termination at both ends, the bus should be grounded at one end only.




When choosing a network topology, it is important to keep in mind the organizational needs and the following criteria: size, cost, transmission speed, tendency to attenuationfault tolerance, and servicing.

The table below lists some of the advantages and disadvantages of the linear bus.
 

  Advantages of linear bus   Disadvantages of linear bus

  • Simple set-up

  • Least expensive layout

  • Uses inexpensive thin coax cable

  • Uses smallest amount of cable

  • Doesn't require a hub

  • Appropriate for small networks

  • For instance, a temporary training room that is set up and torn down quickly

  • Slow

  • Vulnerable to attenuation, or the loss of signal strength over distance

  • Inappropriate for large networks

  • Less fault tolerant


 

 
How computers communicate on a linear bus

A linear bus is called a passive topology. This means that as the signal travels down the network, it is simply passed from one computer to another without any regeneration or amplification, as occurs in an active topology.

The animation below shows how data travels on a linear bus topology.



Transcript



 
Equipment requirements

Equipment requirements for a linear bus network are minimal. Each computer must have:

A network interface card (NIC) with a BNC T connector attached.

One length of cable to reach between each two computers.

The network must have:

  1. A terminator for each end of the network.

  2. If the linear bus is long, you may need repeaters to boost the signal. With thin coax, you need a repeater every 180 meters; with thick coax, every 500 meters.

 

TIP:One meter equals approximately 3.28 feet.




 
Next lesson

In the next lesson, you will learn about the characteristics of the star bus topology.
 
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