The Internet has become an integral part of our society. It not only supports financial transactions and access to knowledge, but also cultivates relationships and allows people to participate in communities that were hard to find before its existence. From reading the news, to shopping, to making phone calls and watching videos, the Internet has certainly surpassed the expectations of its creators.

This vital organ in today's society comprises a large number of networks, administered by different authorities and spanning the entire globe. In this book, we will take a deep look into what constitutes those entities and how they form the skeleton of the Internet. Going beyond the physical infrastructure, the wires and boxes that make up the building blocks of today's Internet, we will study the procedures that allow a network to make optimal use of those building blocks.

As in traditional telecommunication networks, the Internet constituents rely on a team of network designers and managers, for their design, operation and maintenance. While such functions are well studied within the traditional telecommunication theory literature, the Internet imposes constraints that necessitate a whole new array of methods and techniques for the efficient operation of a network. Departing from the traditional circuit-switched paradigm, every unit of information flows independently across the network, from the source to the destination, and thus is much harder to account for.

Since the late 1990s, the research community has been devising techniques that allow the operators of this new kind of network to allocate and manage their networks' resources optimally.