The advantages of the bus topologies are;
- Cheap and quick to install
- Requires the least amount of cable
- Peripherals are easily added
The disadvantages are
- The more computers added means the network speed reduces
- If the backbone cable break the whole network goes down
- Its difficult to identify a problem on the network by location
Star Network
The star topology has a distinct advantage over its counterpart the bus. In this case the star topology has no need to send the information through the network via every computer. It goes from computer to hub to destination, far more direct. Every computer must therefore be connected to the hub with an Ethernet cable, this means a slight problem, more cable is needed, and however, more information can be sent without clashes. When information is sent it contains the I.P address of the recipient computer, this then enables the hub to decipher between destinations to find an exact match.
The advantages of the star network are,
- Information is sent more directly
- It is easy to install and add newer peripherals and computers
- It is easy to manage
- There is no clash of information when it is sent.
- Easy to detect faults
The disadvantages are,
- Lots of cable is needed
- If the hub goes down then the network will not function
- It is more expensive than bus technology
Ring
The ring topology is very similar to the bus in the fact that it must pass through every computer, however it has a variation. The ring network will only pass in one direction, and it passes with the use of a token. The possessor has the token and will send it in the given direction to the recipient. This is called token passing. This is far more efficient as all data is sent in one direction, and only the holder of the token can pass it. The star is different because it is all separately linked; this means they can all send information at the same time in differing directions. For example, if A wanted to send information to B it firstly must possess the token. When it has this it can send information in the direction which the topology was set-up. We will use clockwise in this example. The information would pass through all computers that stand between A and B in a clockwise direction. Once there is no information to be sent, the token will continue to pass around the topology until it is needed by another terminal.
The advantages of the ring topology are;
- Its very efficient
- Computers and peripherals are easily added
- Its easy to maintain
- There is no clash of information when it is sent
- Each computer gets an equal chance to send information
The disadvantages of ring topology;
- If the cable ring breaks then the whole network will not function
- Any computer that has a problem will impact upon the whole network
- The hardware used to implement such a network costs far more than any other system used
- It’s a lot slower under heavy work load
Comparison
When looking at the three topologies it is clear to see that they all have differing set-ups and properties. The bus compared to the star is very different. The star is singularly (per workstation) connected to a hub. This aids information flow but uses a lot more cable. The bus has less cable but is not as efficient. The problem with the bus system is errors in the cable. If there is one error with the cable all the workstations will cease to work. This compared to the star is a stark difference. Defects in cables will only affect the one workstation leaving the rest of the computers to function. A problem would arise when the hub tried to pass information to the workstation with the faulty computer. The ring topology is similar to the bus topology, it has to pass through every work station to work its way to its destination, unlike the bus however the ring sends a token. It sends the token and ensures that only one workstation can send information at a time. The problem with the bus is that when it sends information more than one at a time it will clash, when passing the token this is impossible.
