Now that you’ve got the basics of network communications, it’s time to tackle something more complex. The best place to start is with the most familiar data network: the Internet. It’s not actually a single network, but a collection of networks owned by different network service providers and linked using some common protocols. This chapter describes the structure of the Internet, the devices that hold it together, and the shared protocols that make it possible. You’ll get hands-on experience with what’s going on behind the scenes when your web browser or email client is doing its job, and you’ll use the same messages those tools use to connect your own objects to the Net.