Important knowledge points of Computer Network Fundamentals. The knowledge points outlined in the first chapter include chapter guidance, the definition and function of computer network in the first section, the development of computer network technology in the second section, the classification and main performance indicators of computer network in the third section, and the architecture of computer network in the fourth section. The seven-layer structure of the reference model is very important and should be understood as follows:

Bottom-up: physical layer, internal data link layer, network layer, transport layer, session layer, presentation layer and application layer.

Physical layer: establish physical links between communication systems to realize the transmission of the original bit stream. The equipment working on this floor has a repeater hub network card, and the data transmission unit is bit stream.

Data link layer: it realizes the system identification in the physical network, has the function of framing, and also provides the access control function to provide error-free data transmission in the network that rewards transmission media. The equipment that works on the floor has a switch.

Bridge. A transmission unit is a frame.

Network layer: the unified identification of the system in the whole Internet, which has the function of segment reorganization and addressing, and realizes the function of congestion control.

Transport layer: to realize data communication between processes between hosts. The unit of data transmission is a segment.

Session layer: organizes and synchronizes the communication between various processes on different hosts.

Presentation layer: a method to provide representation for data transmitted between application processes, that is, to determine the coding mode of data in the computer.

Application layer: It provides services (only) directly to the network application process.