Chapter |Intro|: Introduction
Suppose you want to build a computer network, one that has the potential to grow to global scale and support applications as diverse as video conferencing, live and on-demand streaming, e-commerce, social media, automated manufacturing, and more. What available technologies would serve as the underlying building blocks, and what kind of software architecture would you design to integrate these building blocks into an effective communication service? Answering this question is the overriding goal of this book—to describe the available building materials and then to show how they can be used to construct a network from the ground up. Of course the Internet is just such a network, and so we use it as our model.
Today's Internet connects over 22 billion devices. Those devices are widely distributed across the planet (and in low orbit around the planet), where any one of them can send and receive messages with one or more of the other 22 billion devices. The network itself is a massively distributed system, built from hundreds of millions of switching devices. The system is so complex that visualizations of data collected about Internet connectivity—like the one shown in :numref:`Figure %s <fig-net-visualization>`—look more like abstract pieces of art than an engineering diagram.
Visualization of Internet connectivity, with attribution to Barrett Lyon / The Opte Project.
Understanding a system of this scale and complexity requires more than reading a set of specifications. There are just too many details, making it impossible to see the forest for the trees. The key is to start with a sound framework for understanding the problem space, identifying the fundamental challenges that have to be addressed, and exploring the design space of possible solutions. That is the goal of this book.
It's also important to keep in mind that the path from conception to today’s reality is not a straight line, nor is today’s Internet the end of the process. There have been many false starts and stop-gap solutions, followed by years of iterative improvement. This evolution culminates in today’s software and hardware artifacts—many of which are worth looking at in detail—but always keeping in mind that those too will likely change over time. Our goal is not just to explain how the Internet of today works, but to teach the principles that will enable the designers of future networks to build systems that expand on the capabilities available today.