Switching is based on the transmission of information at both ends of the communication needs, with artificial or equipment automatically completed, the information to be transmitted to the appropriate route to meet the requirements of the technology collectively. Switch according to the different working location, can be divided into WAN switches and LAN switches. A wide area switch is a device that performs the exchange of information in a communication system. It is used at the data link layer. The switch has multiple ports, each port has a bridge function that can connect to a local area network or a high-performance server or workstation. In fact, the switch is sometimes referred to as a multi-port bridge. Switches in accordance with the functional area mainly telephone voice switches and Ethernet switches. According to the star topology can be divided into core switches, aggregation switches, access layer switches.