A bus topology uses one cable as a main trunk to connect all of the systems together (shown in Figure.1). A bus topology is very easy to set up and requires no additional hardware such as a hub. The cable is also called a trunk, a backbone, or a segment. With a bus topology, when a computer sends out a signal, the signal travels the cable length in both directions from the sending computer. When the signal reaches the end of the cable length, it bounces back and returns in the direction it came from. This is known as signal bounce. Signal bounce is a problem, because if another signal is sent on the cable length at the same time, the two signals will collide and be destroyed and then must be re transmitted. For this reason, at each end of the cable there is a terminator. The terminator is designed to absorb the signal when the signal reaches the end, preventing signal bounce. If there is no termination, the entire network fails because of signal bounce, which also means that if there is ever a break in the cable, you will have unterminated ends and the entire network will go down, as shown in Figure 2. A bus is a passive topology, which means that the workstations on the bus are not responsible for regenerating the signal as it passes by them. Since the workstations do not play an active role, the workstations are not a requirement of a functioning bus, which means that if a workstation fails, the bus does not fail. But if there is an unterminated end in the bus, the entire network will fail.
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| Figure 1: Bus Topology |
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| Figure 2: A break in the cable with the bus topology |
ADVANTAGES OF BUS TOPOLOGY:
One advantage of a bus topology is cost. A bus topology uses less cable than a star topology or a mesh topology, and you do not need to purchase any additional devices such as hubs. Another advantage of a bus topology is the ease of installation. With a bus topology, you simply connect the workstation to the cable segment or backbone. You need only the amount of cable to connect the workstation to the backbone. The most economical choice for a network topology is a bus topology, because it is easy to work with and a minimal amount of additional devices are required. Most importantly, if a computer fails, the network stays functional.
DISADVANTAGES OF BUS TOPOLOGY:
The main disadvantage of a bus topology is the difficulty of troubleshooting it. When the network goes down, it is usually due to a break in the cable segment. With a large network, this problem can be tough to isolate. Scalability is an important consideration in the dynamic world of networking. Being able to make changes easily within the size and layout of your network can be important in future productivity or downtime. The bus topology is not very scalable.
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