Network topology is simply a geometric representation of the interconnections of the computer on a network. A network topology gives a representation of the types of connections that exists between the devices on the network.
There are five (5) types of topology - Mesh, Star, Bus, Ring and Hybrid. These are as explained below:
Mesh Topology: In a mesh topology, every device is connected to every other device on the network through a dedicated point-to-point link. The major advantage of this topology is that it is quite reliable as a single link does not affect the communication on the other links. Additionally, fault detection on a mesh network is relatively easy. A major disadvantage however, is the need for multiple links across the network which makes it quite tedious to manage. Scalability is also a big issue with this topology because more devices will need more links which is quite expensive and difficult to maintain.
Star Topology: In a star topology, each device on the network is connected to a central point known as the network hub. Unlike the mesh topology, there is no direct connection between the different devices. Devices on the network can only communicate with each other through the hub. The clear advantage of this approach is that it is less expensive because each device requires only a single I/O port that needs to be connected to the hub with only one link. The ease of installation also makes star topology stand out from the other types. A big drawback of this topology type is the fact that failure of the hub can bring down the entire network. Having a single hub controlling the entire network can put a lot of pressure on the hub, and usually will cause the hub to require frequent maintenance.
Bus Topology: Bus topology is made up of a main cable on which devices are connected to through drop lines. A device know as the tap connects the drop line to the main cable. Given that most of the data is transmitted through the main cable, there is usually a limit of drop lines and the distance a main cable should have. The ease of installation and the limited number of cables needed to setup is what makes this topology desirable. Fault detection however, is very difficult in a bus topology. It is also not scalable because there is a limit of how many nodes can be connected to the backbone cable.
Ring Topology: In a ring topology, every device is connected to the two devices on either side of it. There are usually two dedicated point to point links that any given device has with the devices on either sides of it. The structure forms a ring-like structure, thus the name ring topology. Communication on a ring network is usually done in one direction with each device acting as a repeater which forwards data until it reaches the intended receiver device. The ease of installation and that of adding new devices to the network is a major advantage of the ring topology. There are however problems with data traffic because the data is being circulated in a ring. Also given that devices act as repeaters themselves, failure of a device can prevent signals from travelling forward.
Hybrid Topology: Hybrid topology is the combination of two or more of the topology types discussed above. This form of topology is often used in real world applications as it combines the strengths of the different individual topology types to create a more robust network. The hybrid is mostly used because it is easy to scale and integrate new devices easily. While fault detection in this topology remains difficult, it is still the most desired simply because it is the most practical for real-life use.
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