Part I introduces the base concepts and terminology in networking, and establishes an architectural framework for addressing all the challenges that arise when building a global, general-purpose network. It also helps scope the set of problems addressed by the other two parts: Chapter 2 introduces a representative set of applications, setting the stage for understanding the edge software stack described in Part III; and Chapter 3 looks at the design space for switches and links, and then settles on a particular technology—Ethernet—that serves as an exemplar building block for discussing the challenges raised in Part II.