Gateway interconnections are made through various communication paths, including telephone lines, optical fibers, and radio links. Additional networks can be added by linking to new gateways. Information to be delivered to a remote machine is tagged with the computerized address of that particular machine. Once addressed, the information leaves its home network through a gateway. It is routed from gateway to gateway until it reaches the local network containing the destination machine.
Internets have no central control, that is, no single computer directs the flow of information.
This differentiates internets from other types of online computer services, such as CompuServe, America Online, and the Microsoft Network. The Internet Protocol is the basic software used to control an internet. This protocol specifies how gateway machines route information from the sending computer to the recipient computer. Another protocol, Transmission Control Protocol, checks whether the information has arrived at the destination computer and, if not, causes the information to be resent. Even though computer interaction is in its infancy, it has dramatically changed our world, bridging the barriers of time and distance, allowing people to share information and work together.