Network Topology

The physical arrangement of computers and devices is called network topology. The topology of a network determines the manner in which a network is physically connected and shows where resources are located. It is possible that while a network has a certain physical topology, it may be logically connected in a different way. For instance, a network may be physically laid out as a star topology but be logically controlled as a ring. The type of topology that is used will depend on what configuration makes the most sense for the resources involved and the context of the network. In reality, company networks are made up of many smaller networks that may vary greatly in topology.

Ring topology

In a ring topology, devices within the network are laid out in a closed loop. Each system is part of this loop and is connected to the rest of the network through the device on either side of it. The transmission link is unidirectional in a ring topology, so data flows only in one direction. Because there is no central device to which the rest of the network connects, a packet must travel through each device along the ring until it reaches it's destination. In a simple network, this could be a source of failure because if one system goes down there is no way for information to continue flowing through the network. In modern systems, there are redundancies in place to prevent this from happening.

Bus topology

A bus topology uses a single cable as a backbone for the network. Nodes are connected to this cable through drop points and have the ability to look at each packet as it travels along the cable. When a device transmits to another on the network, the packet gets placed on the cable and is examined by each node until the one it's addressed to sees it and pulls it. Because the cable serves the entire network, it is a possible single point of failure.

Star topology

In a star topology, each node is connected to a central device such as a switch. A dedicated link exists between each node and the central device, so devices are not as dependent on each other as they are in other networks. Aside from the central device going down, a node going out will not negatively impact the network. This topology also requires less cabling than other topologies. Most networks are based on a star topology today because this type of network is more resilient than ring or bus.

Mesh topology

The final topology is mesh topology. In a mesh topology, all systems are connected to each other. This topology offers a large amount of redundancy because every node is connected to every other node, but a large amount of cabling is required, and it can be a real mess to handle. A partial mesh topology would be a network where there exists many connections between nodes, but not every node is connected to every other system. The internet is an example of a partial mesh network.

The diagram below illustrates the different network topologies.