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FIGURE 1.6 A typical star topology with a hub

Mickey    Louie


The design of a star topology resembles an old wagon wheel with the wooden spokes extending from the center point. The center point of the wagon wheel would be considered the hub. Like the wagon wheel, the network’s most vulnerable point is the hub. If it fails, the whole system collapses. Fortunately, hub failures are extremely rare.


As with the bus topology, the star topology has advantages and disadvantages. The increasing popularity of the star topology is mainly due to the large number of advantages, which include the following:


■    New stations can be added easily and quickly.


■    A single cable failure won’t bring down the entire network.


■    It is relatively easy to troubleshoot.


The disadvantages of a star topology include the following:


■    Total installation cost can be higher because of the larger number of cables, but prices are constantly becoming more and more competitive.


   It has a single point of failure, the hub.

Ring


In the ring topology, each computer is connected directly to two other computers in the network. Data moves down a one-way path from one computer to another, as shown in Figure 1.7. The good news about laying out cable in a ring is that the cable design is simple. The bad news is that, as with bus topology, any break, such as adding or removing a computer, disrupts the entire network. Also, because you have to “break” the ring in order to add another station, it is very difficult to reconfigure without bringing down the whole network. For this reason, the physical ring topology is seldom used.

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