This text provides an introduction to the concepts that underlie networking technology. This book is accessible to students without technical backgrounds, and also provides material comprehensive enough to challenge the more experienced student. The seven-layer OSI model is used as a framework to provide the background necessary for explaining networking theory and showing interlying dependencies. This second edition includes new exercises and some more challenging ones. In addition, there is increased coverage of some new topics in networking such as some of the new encoding systems, fast Ethernet, 100VganyLan, ADSL and DSL.