Part III focuses on the data that an end user device ships over a network. Ultimately, the data that flows over the network needs to be the data that is useful to the end user, so the end purpose of a network should be to deliver data on behalf of end user applications. Chapter 8 begins the discussion with a detailed look at web, e-mail, and file transfer applications, including the protocols that those applications use. Chapter 9 focuses on some common services that all applications use.