19 DEC 2018

Topologies of computer networks

Last week we analyzed the typologies of computer networks, this week, we will look deeper their topologies. In fact, there are different ones. In addition to considering the definition of each topology, we will also look at the advantages and disadvantages of each one.

The topology of a computer network is the geometric arrangement of the devices connected to it. The most widespread topologies (schematized also in the picture at the end of the article) are:

  • Star: the most common topology among computer networks. Each device is connected to a star-center that routes the network traffic to the other devices. The star-center can be a hub, a switch, a router or an access point (in the case of wireless connections). These networks are highly reliable and scalable (it is simple to add devices). The only disadvantage of the star-center is that in case of fault, it completely interrupts the network communications;
  • Ring: in this network topology each device is connected to two others. Only one device transmits data on the network at a time. A network ring is characterized by a high level of reconfigurability – it is simple to add or remove a device – and it is easy to diagnose in case of failure. This last point, however, is also a disadvantage since a single malfunctioning device can interrupt the data flow on the network;
  • Bus: like the star topology, in this case all the devices are connected via a single shared transmission medium. The advantages are the same as the star topology, however, a fault to the Bus does not completely interrupt network communications because it creates segments able to communicate internally, but not mutually. Devices connected to the Bus topology share the same transmission medium, therefore additional effort is required in the management of communications and the use of protocols that avoid collisions in communications;
  • Tree: the main feature of this computer network topology is that for each pair of devices there is only one path, so it becomes very easy to manage the “routes” for the delivery of information between the various devices inside it. The device at the top of the tree is called “root” – it is a connecting device, router and so on, like the star topology. The devices at the bottom of the tree are called “leaves”;
  • Mesh: can be seen as a combination of the previous topologies with their advantages and disadvantages. A particular type of mesh topology is that called “fully connected”, where every device can speak directly with another, so in terms of reliability this topology is the best, but it is also the most expensive and difficult to manage due to the high number of connections to coordinate.

Which are the topologies of computer networks

Elaborated by Fabrizio Milazzo and Lucia D’Adamo