The book is deliberately focused tightly onmatters concernedwith communication. It avoids excursions into other areas of computer science, such as computer programming, modelling or simulation, not to mention electronics, photonics or mathematics. Such matters are covered in other specialized texts. The reader requires no background in computer communications, only a basic familiarity with computers in general. A knowledge of computer programming is not required although, in a very few places, a little knowledge would aid full understanding of points made. However, this is not crucial to the main plot. Conversely, the author hopes that the book can also offer something to the reader who does have practical experience of computer communications, by setting this experience in an overall context, and revealing alternative possibilities.