Hub repeats everything it receives and can be used to extend the network. However, this can result in a lot of unnecessary traffic being sent to all devices on the network. Hub passes on traffic to the network regardless of the intended destination; the workstations to which the packets are sent use the address information in each packet to work out which packets are meant for them. In a small network repeating is not a problem but for a larger, more heavily used network, another piece of networking equipment (such as a switch) may be required to help reduce the amount of unnecessary traffic being generated.
A hub transmits all data to all hosts
Switch is used to help reduce the amount of unnecessary traffic being generated. Switch controls the flow of network traffic based on the address information in each packet. A switch learns which devices are connected to its ports (by monitoring the packets it receives), and then forwards on packets to the appropriate port only. This allows simultaneous communication across the switch, improving bandwidth. This switching operation reduces the amount of unnecessary traffic that would have occurred if the same information had been sent from every port (as with a hub).
Switch only transmits data between communicating hosts
Switch and hub are often used in the same network; the hub extends the network by providing more ports, and the switch divides the network into smaller, less congested sections. Another advantage with using a switch is that it is possible to mix devices that communicate with different speeds, so one of the workstations connected to the switch could be running 10MB Half-duplex and another 100MB Full-duplex.