Ethernet, Fast Ethernet, FDDI and Token Ring often referred to as traditional LAN, and they are sharing media, sharing of bandwidth shared LAN. In order to increase bandwidth, often using a network router division, will be divided into a network of more than one paragraph, each of the networks have different sub-address, different broadcasting domain, to reduce conflicts on the network, increase network bandwidth. Micro-paragraph of the network can not meet the LAN extension and the new high-bandwidth network applications to the demand, it is said that "traditional local area network has come to an end."

In recent years the exchange processes-LAN technology, to address shared by the LAN network inefficient and can not provide adequate network bandwidth and network expansion and a series of difficult issues. It fundamentally changed the structure of shared local area network, to solve the bandwidth bottleneck. At present, the exchange of Ethernet, token ring exchange, the exchange of FDDI and ATM, such as the exchange of local area networks, Ethernet one of the most extensive exchange. LAN exchange has become the mainstream LAN technology.

Switches provide the ability to bridge the existing network and increase bandwidth capabilities.

For the LAN switches on the bridge with similar because they all operate in the data link layer (level 2), M A C-layer, the inspection of all network traffic into the device address. And the bridge still has some similar switch to maintain an address on the table and used the information to decide how to filter and forward LAN flow.

And bridge different, switches using technology to increase the exchange of data input and output media and installation of the total bandwidth. General switch delay small forward, the economy and can be divided into small network of conflict domain, for each workstation to provide higher bandwidth.

Packet-switched network is the circuit-switched networks and packet switching network after a new exchange network, which mainly used for data communications. Packet switching is a store-and-forward of the exchange, it will at the user's text is divided into a certain length of the packet to packet for store-and-forward, therefore, than the utilization of circuit-switched, than when the message exchange Extensions to small, but with real-time communication capabilities. Packet-switched TDM principle of the use of statistics, a data link multiplexing into multiple Luojixindao, eventually forming an Caller, Called party transmission of information between the access road, called the VC (VC) to achieve data Packet sent.

Packet switching network has the following characteristics:

(1) packet switching with multiple Luojixindao the capacity utilization rate is high trunk circuits

(2) can be realized packet switching codes of the different online, the rate between the terminal and a point of order Interoperability;

(3) The packet switching error detection and correction of the capacity of the transmission circuit is a very small error rate

(4) packet-switched network-management capabilities.

Packet switching the basic business SVC (SVC) and PVC (PVC) two. SVC as telephone circuit, that is, two data communication terminals to be used when the first call to establish procedures for circuit (VC), and then sent the data, communications rewirable procedures used after the removal of VC. PVC as green, in the net division between the two terminals for the period of the contract to provide permanent logical connection, no call set-up and rewirable procedures, the data transmission phase, with the SVC the same.