This is the sixth edition of the most authoritative book on modern network technologies, written by recognized expert Andrew Tanenbaum, co-authored with Google specialist David Weatherall and University of Chicago professor Nick Feemster. The first version of this classic work was published back in 1980, and since then, each edition of the book has consistently become a bestseller. The book consistently sets out the basic concepts that determine the current state of computer networks and trends in their development. The authors explain in detail the structure and principles of operation of hardware and software, consider all aspects and levels of networking - from physical to applied. The presentation of theoretical principles is complemented by vivid, illustrative examples of the functioning of the Internet and computer networks of various types. Much attention is paid to network security. The sixth edition has been completely redesigned to take into account changes in network technology in recent years, and, in particular, covers technologies such as DOCSIS, 4G and 5G, 802.11ax wireless networks, 100-Gigabit Ethernet networks, Internet of Things, modern transport CUBIC TCP, QUIC and BBR protocols, software-defined networks and much more.