# LAN Topologies

There are two major types of topologies, namely Physical and Logical. The physical topology of a network refers to the layout of cables, computers and other peripherals. Logical topology is the method used to pass the information between the computers.

We will now look at the the most common types of physical topologies: Bus, Hub/Star and Ring

## THE PHYSICAL BUS TOPOLOGY

Bus topology is fairly old and are not majorly used in today’s modern world.With the Bus topology, all devices are directly connected to a main channel that transports the data. Traffic generated by any computer is transferred across this channel and is received by all workstations. This works well in a small network of 2-5 computers, but as the number of computers increases so does the network traffic and this causes a negative impact on the overall performance of the system.

The above is a simple diagrammatic representation of the physical bus topology. From the above diagram, we can see that all the devices/workstations are centrally connected to one single channel. Any communication between any of the workstations has to to be transmitted via the central channel, regardless of the priority of the data, or any other factor that may occur.

If the bus, i.e. the central channel is damaged anywhere in its path, then it will most certainly cause the network to stop working or, cause a huge communication gap between the workstations.

## THE PHYSICAL HUB OR STAR TOPOLOGY

The Star or Hub topology is one of the most common network topologies found in most offices and home networks these days. It has become very popular as opposed to the bus topology because it is a much economical option and easy to configure as well.

The advantage of the star topology is that if one computer on the star topology fails, then the damage is restricted to that single device, while the rest of the devices can continue to function unaffected.

The above is a diagrammatic representation of the star topology. We can clearly see that each of the workstations has a separate connection to the central hub, due to which each of them can function as a separate unit.

## THE PHYSICAL RING TOPOLOGY

In the ring topology, workstations are connected on a single circular cable. Unlike the bus topology, there are no closed ends. The data travels in a circular fashion around the loop in one direction and passes through each computer, and sends it to the next device. If implemented on a larger scale, multiple LANs can be connected to each other in a ring topology.

The method of data transmission in a ring topology is called token passing. A token can be defined as a series of bits which contains control information. Possession of the token allows a network device to transmit data to the network. Each network is allotted only one token.

## THE PHYSICAL MESH TOPOLOGY

In a mesh topology, each workstation is connected to all other devices via a separate cable. This setup allows multiple pathways in a network. Thus, in a mesh topology, if one workstation fails, the entire network does not get compromised. The major advantage of mesh topology is that it provides backup facility, which is very important if used in large companies.

## THE PHYSICAL HYBRID TOPOLOGY

The hybrid topology, as the name suggests, is a combination of two or more topologies, which form a complete network. We will now look at the most common hybrid topologies.

### STAR-BUS

In a star-bus topology, multiple networks which are aligned in the star topology network formation are linked to a central bus connection. In this topology, if a computer fails, it will not affect the rest of the network. However, if the central component, or hub, that attaches all computers in a star, fails, then there is a risk of the entire network being compromised.

### STAR-RING

In the Star-Ring topology, the workstations are connected to a central hub as in a star network formation.Like the star-bus topology, if a single computer fails, it will not affect the rest of the network. By the use of tokens, each computer in a star-ring topology has an equal chance of communicating.