What are the commonly used data exchange technologies and explain their characteristics?

A: Generally speaking, there are three data transmission technologies used in network systems: circuit switching, message switching and packet switching.

The principle of circuit switching is that there is a dedicated physical link between the source node and the destination node during data transmission, and this link will be maintained until the end of data transmission. If the traffic between these two nodes is heavy, multiple connections can be established at the same time. Using this technology, an end-to-end line will be established in advance before transmitting data. The advantage of circuit switching is that data transmission is reliable and fast, and the original order is maintained. However, once the communication parties have the channel, even if the data is not transmitted, other users can't use it, which wastes resources. Circuit switching is suitable for high-quality and large-scale data transmission. Usually a telephone communication network.

Message switching In order to solve the defect that circuit switching occupies channels, message switching came into being. Its principle is that data is transmitted in units of messages, and the length is unlimited and variable. The data transmission process adopts the store-and-forward mode. When sending a message, the sender appends the destination address to the message, and the routing node forwards the message to the next node according to the address information on the message, thus completing the whole transmission process in a relay way. After receiving the message, each node will temporarily store and check whether there is any error, then find out the address of the next node with a suitable route through the routing information, and then transmit the message to the next node. In this process, the transmission of messages only occupies a section of the line between two nodes, while other sections can transmit messages of other users. Therefore, this solution will not occupy all channels between terminals like circuit switching. However, there will be a delay when the message passes through the node. The delay includes the time required to receive all bits of the message, the waiting time and the queuing delay required to send to the next node. Compared with circuit switching, message switching has the following advantages: high line efficiency; Nodes can temporarily store messages and perform error control and transcoding on the messages; In the circuit-switched network, you will not be able to receive some information when the traffic is heavy, but you can still do it in the message-switched network, but the delay will be greater; Messages can be conveniently sent to multiple destination nodes; Establish message priority so that messages with high priority are transmitted first.

In order to make better use of channel resources and reduce the burstiness of data in nodes, packet switching is developed on the basis of message exchange. In packet-switched networks, there is an upper limit on the length of each packet, so a long message will be divided into several parts. Each packet contains data and a destination address. The transmission process is similar to message exchange, except that the length of each packet is limited, which reduces the burden on nodes and improves the network transmission performance. The characteristics of packet switching are: