This book includes the Questions and Answers most likely o be asked in MCA and B.E. (Comp. Sci.) and other IT related courses. It has ten Chapters and each Chapter contains important questions with answers. This book covers questions related to Physical layer, Data Link Layer, Network Layer and Application Layer of OSI model. The book also includes questions and answers on Router configuration and different LAN Technologies. Besides this, Questions with their answers are also added on ATM, ISDN and Frame Relay System containing many illustrations, . Ample number of diagrams is used to illustrate the answers for easy understanding. Concept of Network Security, transmission Control Protocol and User Datagram Protocol are explained with easy-to-understand language. Internet Protocol, WWW, Email and Cryptography are also discussed in a simple and lucid manner. This guide will equally prove helpful for answering questions asked in M.Sc. (IT), DOEACC (‘B’ Level), B.E., PGDCA and other IT related examinations conducted by Universities and Technical Colleges. In addition, sample papers are also added at the end of this book to evaluate the progress by users of this guide. A comprehensive glossary of technical terms is also added at the end of this book to clarifying the subject matter.