This edition of the popular book, Computer Networks, has been updated to reflect technological developments since the previous edition. Computer networks is an evolving technology, and it is developing at a fast pace. This book is one of the most popular resources to learn about the subject. Each edition is updated to reflect the latest developments in the field, and each time, there are a lot of new topics as the technology advances rapidly. Computer Networks begins with an introduction to computer networks. It discusses the uses of computer networks, network hardware, and software and reference models. This chapter also takes a look at some example networks like the Internet, Ethernet, and wireless networks. The organizations that define networking standards are introduced. In the next chapter, the author discusses the physical layer of networks. It first takes a look at the fundamentals of data communication and then looks at various technologies used in data transmission - transmission media, wireless communication, satellite transmission, telephone networks, mobile telephone network, and cable television. The third chapter looks at the data link layers. It first discusses the design issues for this layer and error detection and correction. Then, the various protocols relevant to this layer are introduced. Chapter 4 focuses on the medium access sub layer. This section covers channel allocation problems, multiple access protocols, Ethernet, wireless LANs, broadband wireless, Blue-tooth and data link layer switching. Chapter 5 discusses the network layer. It concentrates on the various aspects of this layer - design issues, routing algorithms, congestion control algorithms, quality of service, and the network layer on the Internet. Chapter 6 is about the transport layer. It discusses transport service, elements of transport protocols, simple transport protocol, Internet transport protocols (UDP, TCP), and performance issues. The application layer section looks at Domain Name Service (DNS), electronic mail, the World Wide Web, and multimedia. The next chapter discusses network security. It covers cryptography, symmetric-key algorithms, public-key algorithms, digital signatures, managing public keys, communication security, email security, authentication protocol, web security and social issues like privacy, copyright, and freedom of speech. The next chapter provides a list of further reading. The book ends with alphabetical bibliography and index. The updated features in this edition include coverage of Bluetooth, 802.1B wireless LANs, and 3G cellular systems. The section on security has been thoroughly revised and updated. It also includes expanded coverage of multimedia networking, coverage of current IP addressing solutions, and extended coverage of quality of service. Each chapter ends with a summary and problems and lab exercises.