This book is intended to offer an in-depth knowledge of the subject, COMPUTER NETWORK with a new approach for not only the fourth/fifth semester students of BE/B.Tech of Gujarat Technological University but also for students of any university dealing with the same subject. Several features of this text are designed to make it particularly easy for students to understand data communications and networking. This book is written for both an academic and a professional audience. The book can be used as a self-study guide for interested professionals. As a textbook, it can be used for a one-semester or one-quarter course. The chapters are organized to provide a great deal of flexibility.