Computer Networks is a core subject which explains how a computer connects with other computers. TCP/IP protocol suite is the basis on which computer connectivity can be achieved. The book “Introduction to Computer networks 2nd edition” has been written for MCA 2nd year students of Abdul Kalam Technical University. The book has been written according to the syllabus of the subject Computer Networks and concepts have been explained well through the help of examples and diagrams. The book contains Introduction to Computer Networks, its types and topologies, the Application Layer and its different protocols, the Transport Layer Protocols, flow control and congestion control, the Network Layer, IPv4 and IPv6 with addressing the Data Link Layer and its protocols, the Physical Layer. Also solved numerical problems are included at the end so that students can comprehend the concepts well. The book will be beneficial to students of other universities as well who are studying this subject. This book is the second edition of “Introduction to Computer Networks” book which has appended a broader range of topics to its first edition.