This book is designed to help the reader understand the basics, concepts and principles of implementing computer networks. The book also includes a brief introduction to client and server operating systems running on network computers. The book includes the history of the development of computer networks, accepted terminology, network theory, established standards and methods of implementing local and global computer networks. Particular attention is paid to network protocols and the operation of protocols at all levels of the computer network model. The book describes in detail the compatibility of networks running on different platforms and in different protocols and operating systems, as well as security and remote access issues, private virtual computing networks, networks with thin clients, network administration and troubleshooting. The nearest and more distant prospects for the development of network technologies are being considered.