Briefly describe what data communication is and what its characteristics are.

Data communication is a communication form that integrates data processing and transmission, realizes the reception, storage, processing and transmission of digital information, and controls, checks and manages the information flow. Data communication has the following characteristics:

1. Data communication realizes communication between computers or between people, while telephone system mainly completes communication between people.

Computers do not have the thinking ability of human brains, but rely on pre-programmed programs to complete all the work. Therefore, the communication process between computers needs to define strict communication protocols, which are much more complicated than the standards in the telephone system.

2. Data communication requires high data transmission rate.

The transmission rate of data signals varies according to the channel used.

Data communication technology has experienced four stages of development:

Circuit switching technology, message switching technology, packet switching technology and ATM technology. Both public telephone network (PSTN network) and mobile network (including GSM network and CDMA network) adopt circuit switching technology.

Its basic feature is the connection-oriented mode. Before the two parties communicate, a fixed bandwidth communication line needs to be allocated. Both parties will occupy the allocated resources until the communication ends, and relevant signaling protocols need to be used in the process of establishing and releasing the circuit.