This illustration shows, from left to right: A source computer connected to a router labeled "Packet switch." Inside the router is a single blue cube labeled "Message." This router is connected to a second, empty router, which is connected to a computer labeled "Destination."

This illustration shows, from left to right: A source computer with a slim blue packet emerging from it. This computer is connected to a router labeled "Packet switch." Inside the router is a slim blue packet. This router is connected to a second router labeled "Packet switch," which also contains a slim blue packet. The second router is connected to a destination computer, which is receiving a slim blue packet.