This illustration uses the image first introduced in figure 1.1 and repeated in subsequent chapters, of the interconnected networks that make up the Internet. These networks include a mobile network, a national or global ISP, a local or regional ISP, a home network, and an enterprise network. This figure focuses on the Enterprise Network, which includes several routers and link-layer switches sending signals to desktop computers and servers, and a base station sending wireless signals to laptops and a tablet device. Blue arrows track the six link-layer hops between the wireless host and server: the arrows point back and forth between the server and a link-layer switch, between the link-layer switch and a router, between that router and a second router, between the second router and a second link-layer switch, between the link-layer switch and a base station, and between the base station and the wireless devices.