For years, college courses in computer networking were taught with little or no hands-on
experience. For various reasons, including some good ones, instructors approached the principles
of computer networking primarily through equations, analyses, and abstract descriptions
of protocol stacks. Textbooks might have included code, but it would have been unconnected
to anything students could get their hands on. We believe, however, that students learn better
when they can see (and then build) concrete examples of the principles at work. And, fortunately,
things have changed. The Internet has become a part of everyday life, and access
to its services is readily available to most students (and their programs). Moreover, copious
examples—good and bad—of nontrivial software are freely available.
