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Network Topologies

A topology refers to both the physical and logical layout of a network. The physical topology of a network refers to the actual layout of the computer cables and other network devices. The logical topology of a network, on the other hand, refers to the way in which the network appears to the devices that use it.

Several topologies are in use for networks today. Some of the more common include the bus, ring, star, mesh, and wireless topologies. The following sections provide an overview of each.

Bus Topology

A bus network uses a trunk or backbone to which all of the computers on the network connect. Systems connect to this backbone using T connectors or taps. To avoid signal reflection, a physical bus topology requires that each end of the physical bus be terminated. Figure 3 shows an example of a physical bus topology.

Figure 3 Physical bus topology.


The most common implementation of a linear bus is the IEEE 802.3 standard. Table 2 summarizes the advantages and disadvantages of the bus topology.

Table 2 Advantages and Disadvantages of the Bus Topology

Advantages

Disadvantages

Compared to other topologies, a bus is cheap and easy to implement.

There might be network disruption when computers are added or removed.

Requires less cable than other topologies.

Because all systems on the network connect to a single backbone, a break in the cable will prevent all systems from accessing the network.

Does not use any specialized network equipment.

Difficult to troubleshoot.



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