The book computer Networks provides a comprehensive introduction to the concepts and principles of data communication and networking. It covers the fundamental components involved in data transmission, the various types of computer networks, and their architectures. The book introduces key protocols and standards and explains how data travels across different layers of the OSI and TCP/IP models. It explores physical transmission methods, error detection and correction techniques, switching methods, and multiple access strategies. It also delves into network layer functions such as routing and addressing, transport layer protocols like TCP and UDP, and application-level services including DNS, email, FTP, and web communication. Security mechanisms like PGP and SSH are also discussed. The book is structured to build foundational knowledge and is widely used in academic settings for undergraduate computer science and engineering courses.