The main functions of the switch include physical addressing, network topology, error checking, frame sequence, and flow control. Switches also have some new features, such as support for VLAN (virtual LAN), support for link aggregation, and even firewall functionality. The history of the exchange of electrical signals should be traced back to the early days of the telephone. When the telephone is invented, it takes only one long wire, plus two phones at the end, to make a voice conversation between two people far apart.

1. In terms of the OSI architecture, the hub belongs to the first layer of physical layer equipment, while the switch belongs to OSI's second layer data link layer device. That is a hub is only for data transmission have the effect of synchronization, amplification and plastic, short for data transmission in the frame = fragments cannot effectively deal with, can't guarantee the completeness and correctness of data transmission; The switch can not only synchronize, enlarge and reshape data, but also can filter short frames and fragments.

2. From the way of working, a hub is a kind of broadcasting mode, meaning that the hub port work, all the other ports are able to hear the information, easy to produce the broadcast storm, when the network is larger network performance will be badly affected. And switches will be able to avoid this kind of phenomenon, when the switch work, only request mutual response between the port and destination port without affecting the other ports, so switch to separate collision domains and effectively inhibit the generation of broadcast storm.

3. From the point of bandwidth, hubs, regardless of how many ports are all ports are sharing a bandwidth, at the same time there can only be two ports transmit data, and the other port can only wait for, at the same time a hub can only work in half duplex mode; For switches, each port has an exclusive bandwidth, when two ports work, does not affect the other port to the switch at the same time can not only work in half duplex mode and can work in full duplex mode.