Network topology refers to the layout of the various devices within a network. When we say ‘Layout’ it makes us think of physical locations and that gives the impression that network topology has to do with where the various devices in a network are placed. That’s not the case. Network topology has to do with how devices are connecting to each i.e. their hierarchy.
This hierarchy may be physical in the case of a wired network, or it may be virtual in the case of a wireless network. As end users connecting to a WiFi network, we never really do anything about the layout i.e. network topology. It’s automatically set for us.
A network topology defines how the devices in a network are connected to each other, and to the central hub that forms the network. For example, in some layouts, all devices are connected directly to the central hub which directs traffic. In other layouts, each device is connected to two other devices on the network.
There are five general layouts that networks follow though it is rare for a network to adhere strictly to one layout. Often, networks are a mix of two layouts.
The five layouts are;
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Imagine a route that a bus follows. Along that route, there are several stops that it makes to pick up more passengers, or to drop some off. That is basically the structure of a bus topology. The data in the network travels along a single route and the devices are all connected to this one route at specific nodes. When the data reaches the node it needs to send or receive information from, it does so.
A bus topology is used for small, wired networks. Adding too many devices to this network not only makes it harder to manage but it also slows down the speed of the network.
In a ring topology, each device is connected to two other devices on the network. Think of a group of children sitting around a campfire, holding hands. Each child can hold hands with two other children, and no more. That is basically the layout of a ring topology whereby a device is directly connected to two other devices.
The problem with this type of network is that if it breaks down anywhere, it will cause the entire network to go down. Communication can only take place if all devices on the network have an active connection.
In a Star topology, each device is connected to a central hub. Thing of it as watching TV at home. Everyone has their own connection and receives their own transmission of the channel they’re watching or think of it as our solar system. The planets are the different devices on the network circling the one sun and receiving heat and light from it.
This sort of topology is most commonly found in homes where our PCs, phones, and tablets are all directly connected to a router or in coffee shops that offer free WiFi and allow you to join a larger public network. The advantages of this type of layout are obvious; it’s easy to set up, you can add a large number of devices, and adding or removing a device is simple and it doesn’t break the network.
Much like our example of the solar system though, if a star topology exists within a wireless network, the further a device is from the central hub i.e. your router, the weaker the signal the devices get. This is akin to planets that are further away from the sun receiving less light and heat.
A tree topology is a mix of the bus and star topology and the best example of this type of topology is the internet and how we connect to it. Let’s say there’s a city with exactly five homes in it. Each home has its own WiFi network and all the devices in that home connect to the router in a star layout.
The routers then connect to the main ISP provider in a bus topology i.e. each has its dedicated position on the network. This is of course a very simplified example that describes this type of topology and connecting to the internet is far more complex.
A tree topology has hierarchical layers that define access levels for the devices connected within it and it’s costly to set up. It’s best for large companies that need to control network access within a building or over larger geographically dispersed locations.
In a mesh topology, each device is connected to every other device on the network. This makes it an extremely reliable, and fast layout because data doesn’t have to follow a long path to get to the right device. It can travel directly between the devices.
A mesh network is more expensive to set up and requires special hardware that can support it. It is more costly however, it is faster, more scalable, and suitable for wireless networks.
Who Sets The Topology?
The topology for end users who have a broadband connection is decided by the hardware their ISP provides them. You have little say in it unless you have the expertise to change it. You can change the topology of your network but it isn’t as easy as changing the WiFi network name, or resetting your router. It’s far more complex.
For LANs such as those in universities and offices, the network administrator decides which topology will suit the needs of everyone connected to the network. This includes not just designing the topology but also setting up the hardware to create it. As such, you can imagine that there is a lot to consider since buying hardware is involved and an incorrect purchase can cost a lot. What’s more, if the wrong type of topology is selected, replacing it is costly not just in terms of money but also in time.