The Internet is used as the principle example of a communication syste m, allowing the reader to follow the system from the application layer s, with source coding and security, through the network, with naming a nd routing algorithms, down to transport and physical aspects of a com munication system. Modern techniques such as mobile radio, Voice over IP, and ASDL, are covered, while more traditional aspects such as circ uit switching, which still form a significant part of current systems, are not overlooked. By providing a technical introduction and includi ng application examples, this...