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Welcome to the third edition of Computer Networking: A Top-Down Approach Featuring the Internet. Since the publication of the first edition four years ago, our book has been adopted for use at hundreds of colleges and universities, translated into more than 10 languages, and used by over one-hundred thousand students and practitioners worldwide. We've heard from many of these readers and have been overwhelmed by the positive response.

We think one important reason for this success has been that the book offers a fresh approach to computer networking instruction. Why is a fresh approach needed? In recent years we have witnessed two revolutionary changes in the field of networking-changes not reflected in books based on a 1980's or early-to-mid 1990's approach towards networking. First, the Internet has taken over computer networking. Any serious discussion about computer networking today has to be done with the Internet in mind. Second, the biggest" growth area" in the field of networking has arguably been in networking services and applications, as evidenced by the emergence of the Web, ubiquitous e-mail use, audio and video streaming, Internet phone, instant messaging, peer-to-peer applications, and online commerce.