Whatever information is sent across the Internet (e-mail, Web page, and so on) is firstly broken into 1,500-byte packets. The packets are transmitted across several routers, each one sending the packet to the target device. The packets will be transmitted through the best existing route. This type of network is called a packet-switched network. Each packet contains the same route, or none of the packets could take the same route. Once the packets show up at the destination computer, they are reassembled. This process goes so quickly that you would not even know that the file was chopped into 1,500-byte packets and after that reassembled.

A figure explains how a packet-switched network operates. The routers in the Internet are linked together in a web. The packets follow the path of least resistance to make sure they arrive at their destination in a reasonable amount of time. It seems logical that the packets would go through the least number of routers to get to its destination. However, sometimes that is not sufficient, because there may be congestion clogging the ideal path. Routers send the traffic around the congested portions of the Internet for improved speed and efficiency.

This may seem like a very complex system—as compared to the process followed when placing a telephone call—but the system works for two important reasons: The network can balance the load across various pieces of equipment on a millisecond-by-millisecond basis.

If there is an issue with one piece of equipment in the network while a message is being transmitted, packets can be routed around the problem to make sure that the whole message is received.

The routers that make up the important part of the Internet can rearrange the paths that packets take because they look at all the information surrounding the data packet, and they give the information each other about line conditions, like problems sending and receiving data on different parts of the Internet.