Tutorial : NETWORK TOPOLOGIES

What is a network topology?

A topology describes the arrangement of the network, which includes all the nodes (components), and their connecting lines.

A network geometry is split into two categories: physical topology and logical (Signal) topology.

The physical topology of a network is the actual physical layout of the devices which are connected in that network. The following are the most common physical topologies:

In a bus network topology, every node is connected to a main cable which runs throughout the topology, with terminators placed on the ends to prevent damage in the topology. Should a component connected in the bus network fail, the other components will operate as normal, however, should the main connector fail, all components in the network will not function.

In a Star network topology, every node in the network is indirectly connected to every other node in the network generally via a hub, server, or central computer. Should any component (other than the central connector) in a star network topology fail, only that component will not work, the other components will resume operation as normal, however should the central connector fail, all components in the network will be affected . The star network topology acts as a client server network connection.

Every node in the ring network topology is connected to the nodes next to it in a closed loop configuration. The ring topology is one of the simplest and cheapest network topologies to set up. It is also the most insecure network topologies. Should one of the nodes or connectors in this network fail, all the components will be affected.

The “token ring” is often thought by many to be an actual topology, but it is actually a protocol which is used in both the star and ring network topologies. This protocol works by attaching a signal to a figurative “token” as it travels between nodes in the network.

Mesh Topology

A mesh network topology is a topology which connects one node in a network to every other node in a network (As seen in the illustration above, the blue lines show how the one node is connected to every other node in the network).

The above image is an example of a full mesh topology. A full mesh topology connects one node DIRECTLY to all other nodes in the network. In a partial mesh topology the nodes are often connected to hubs which are connected to other hubs which relay and indirect connection from one node to all other nodes in the network.

 A mesh network acts as a Peer-to-Peer network, it is also the most secure network topology as if one node fails, all the other nodes will continue to operate as normal. The mesh network is also the most expensive network to set up.

Here is one of the more uncommon network topologies:

Hierarchical Topology

The hierarchical network topology is designed to help create a network in separate layers. Each layer has specific tasks which it must perform which means that it is very important to choose the right components for each layer. The hierarchical topology is usually divided into the following layers:

•          Core Layer: usually made up of hubs/switches and with high-speed cabling (fibre optic cables). The core layer is considered to be the backbone of the network.

•           Distribution Layer: this layer is usually made up of switches and LAN-based routers, and it is responsible for ensuring that the packets are properly routed in the network.

•           Access Layer: Usually referred to as the desktop layer. This layer is tasked with connecting client nodes in a network and ensuring that the packets are delivered to the end user.

Logical (or signal) topology refers to the nature in which a topology operates. In most cases, the logical topology is the same as the physical topology, but this is not always true.

For example, a network topology may for instance have the physical topology of a star, but in terms of the logically topology it may operate as a bus, or even a ring network.

Why do we use network topologies?

There are many reasons to use network topologies, some of which are as follows:

•        Network topologies make communication between devices on the same network easier.

•          Many business’ use network topologies to save on hardware and software costs.

•          Easier sharing of data – most network topologies have a centralised administration system, which can access all the data needed from the other nodes on the network.

•          Reduces data duplication and the risk of data corruption.

How do the above reasons help us?

•          It is easier for a node on the network to access, communicate or get data from other nodes on the network.

•          You save on hardware costs because the computers/nodes on the network can share peripheral devices connected in the network. This means that there isn’t a need for every individual node to have its own printer, scanner or other peripheral devices.

•          The administrator can access the data from all nodes from a single node on the network.

•          Data corruption and data duplication is prevented as the same files are uploaded to a network, and therefore if they are copied, or downloaded, the data will not be duplicated, nor can it become corrupted.

The following video on network topologies might assist you in your studies of the topic:

             

For more information on the Bus, star, ring and mesh network topology click here.

Click here for more about the hierarchical topolgy as a whole.

Click here for more about the layers of the hierarchical topology.


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