The book consists of 20 chapters, divided into five parts. In chapter 1, the introduction covers the generation and development of the network, the main functions, classification, and network architecture and the ISO/OSI reference model. The first part (chapter 2 ~ 3) introduction to data communication knowledge, basic concept and basic theories involved in data communication, the transmission medium, the multiplexing technology, data exchange technology, modem technology and the physical layer interface technology, etc. The second part (chapters 4-6) discusses various underlying networking technologies, involving various wan, LAN and high-speed LAN technologies. The third part (chapter 7 ~ 11) discusses network interconnection technology and its related protocols, which involve network interconnection, TCP/IP reference model, IP, ARP and ICMP, IP routing, and TCP and UDP. The fourth part (chapter 12 ~ 17) discuss interaction network application mode as well as a variety of specific network applications, client/server model, socket programming interface, the domain name system (DNS), Telnet (Telnet), file transfer and access, E-mail and the world wide web. Part v (chapter 18-19) discusses network security and management. Finally, chapter 20 briefly introduces the future development of network technology. Book is mainly for computer majors in colleges and universities undergraduate and junior graduate student as the computer network curriculum teaching material use, but also for computer network designers, developers, and managers used as technical reference books.