Lesson 01: Introduction to Computer Networks
Concept : A computer network is a system of many discrete and independent working computer systems connected through communication lines and communication equipment, and a system that complies with certain protocols and uses software to realize resource sharing.
Composition : Divided into three parts: hardware, software, and protocol.
The division of agreement: The agreement is divided into the international standard OSI/RM and the accepted standard TCP/IP.
Classification : (1) According to the distribution range: local area network, metropolitan area network, wide area network.
(2) According to topological structure: star, ring, tree.
(3) Other categories: campus network and enterprise network; public network and professional network; communication network ISP and information network ICP; backbone network and access network; wired network and wireless network, etc.
Protocols and standards : OSI/RM (Development System Reference Model) seven layers are application layer, presentation layer, session layer, transport layer, network layer, data link layer, and physical layer.
TCP/IP four-layer protocol structure: application layer, transport layer, internet layer, network interface layer.
Comparison of seven-layer OSI and four-layer TCP/IP protocol:
Functions of each layer of the seven-layer protocol :
The lower layer is mainly used for communication, and the upper layer is mainly used for resource management.
The entire process of network data transmission: data encapsulation (packaging the data in layers) The
entire process of network data transmission: data decapsulation (optical fiber network cable equipment)
The presentation layer implements data compression.
The data unit processed by the data link layer is a frame, the physical layer is a bit, the network layer is a packet, and the transport layer is a message.
The service access point of the network layer is the IP address, and the end-to-end is the transport layer.