Book excerpt: Computer Networks and Open Systems: An Application Development Perspective covers principles, theory, and techniques of networks and open systems from a practical perspective, using real system and network applications as its basis. The selection of topics forms a core of material in computer networking, emphasizing methods and the environment for application development. The text aims to make readers immediately comfortable in today's networking environment while equipping them to keep pace in one of the fastest moving and most exciting areas of computer system development. Students will enter the study of networking through their own experience as a network users, and they will have the opportunity to practice the kind of networking tasks they will perform in the workplace.