15.5.6 Routing In Perspective

Routing is one of the fundamental technologies that distinguishes an internetwork from a simple local network.

Ethernet switches deliver frames within a single LAN using MAC addresses. Routers deliver packets between independent networks using logical IP addresses and routing tables. By forwarding packets from one router to the next, they create the worldwide communication infrastructure that we know as the Internet.

Although modern routing protocols are highly sophisticated, the underlying principle is remarkably simple. Every router examines the destination address of each packet and forwards it toward the next network on its journey. Repeating this process many times allows packets to travel across continents and oceans before finally reaching their destination.

The next section examines the transport protocols that provide reliable end-to-end communication between applications running on those interconnected networks.