This simple, well organized book provides the theory as well as the practical aspects of computer network. It covers the pillars of a computer network, like transmission, data transfer, and communication.It covers foundational concepts, explaining the OSI and TCP/IP models, digital transmission, interfaces, modems, and media characteristics like attenuation and throughput. It focuses on telephony, multiplexing techniques (FDM, TDM, and WDM), error correction, and ISDN. The book goes deep into network infrastructure, detailing devices like repeaters, bridges, and routers. It explores the transport layer and upper OSI layers for reliable data delivery and application formatting. It discusses network connections, encoding, error detection, Ethernet, switching, bridging, and routing. The book covers advanced topics like MPLS, mobile routing, TCP, RPC, congestion control, and QoS. It focuses on network security, including encryption, authentication, firewalls, and intrusion detection systems.This book is an ideal guide for beginners, irrespective of their roles, to learn and become masters in computer networking. This book is targeted for a wide and diverse readership, from school students to software professionals to academic researchers.