By the word ‘Internet’ we refer to the international system of digital communication, emerging from the agglomeration of thousands of networks that interact through a number of common protocols world-wide. It cannot be physically perceived, or meaningfully located in space and time, over and above the set of interacting networks that constitute it. It is a collaborative initiative of services and resources, each network being accountable only for its own proper functioning. Thus, nobody is ultimately responsible for it as a single enterprise. Chapter 2 provides a brief history of the Internet and some background on how these networks operate.