The first network which was set up was a bus network. Effectively all computers connect directly into a single bus which runs around all of the computers. The bus is simply just a cable which carries the signal from one PC to another. Below is a diagram of the bus.

Packets placed on the bus will travel along the bus until they reach the end of the bus. Each PC will listen to the bus and will retrieve packets which are destined for them. In the early days of computer networks the bus was a simple cable and each PC would physically tap into the network by hammering a connector into the cable. Although this was a simple way to network computers it did pose a number of problems. If the tap was placed at the wrong point then the cable will become damaged and may no longer transmit data if the tap was removed. Also if the tap was hit too far into the cable this could cause damage and packet loss.

Modern bus networks are more like a daisy chain of PC's rather than all PC's connecting into a bus. We call this a logical bus but it is still drawn as the diagram above. Hubs also contain a bus inside them and use this to propagate packets.

Bus networks have a number of advantages and disadvantages-

Advantages

• Cheap costs as only cabling is required.
• Simple to set up and maintain.
• Ideal for small or home networks as they lack a lot of the complexity of other types of network.

Disadvantages

• If the bus is cut then the whole network will go down.
• The more PC's which are on the network then the higher the chance of collisions
• Limited number of PC's can be placed onto a single bus.
• Performance is weak if there are a large number of PC's connected or network traffic is high.