A switch is a device that performs information exchange functions in a communication system.
In computer network systems, the concept of switching is an improvement over the shared mode of operation. The HUB hub is a shared device. The HUB itself cannot identify the destination address. When the A host in the same LAN transmits data to the B host, the data packet is transmitted by broadcast on the HUB-based network. The terminal determines whether to receive by verifying the address information of the packet header. In this mode of operation, only one group of data frames can be transmitted on the network at the same time. If a collision occurs, it must be retried. This way is to share network bandwidth.