In the earlier example, we study how a router could be used locally. Now, let us broaden the scope of routers that do include the functionality across the Internet.

For comparison purposes, let's talk first about how a call is routed across the country. They say it's the birthday of Aunt Sadie and instead send an e-mail, you want to call. When you make a long distance call, the phone system creates a stable circuit between your phone and the Aunt Jessie. The circuit may involve hopping through a series of actions, including fiber-optics, copper wires, and satellites. This end-to-end chain that ensures the quality of the line between you and Aunt Jessie will be stable. However, if the satellite is disconnected or work crews cut the fiber optic cable, your conversation with Aunt Sadie would stop. The Internet avoids this problem by making the "call" in a completely different way.