1975
Router
Virginia Strazisar (Dates Unavailable)
It is not uncommon for engineers to experience a paradigm shift or a reconceptualization—a change in the conventional way of thinking that offers significant advantages. The switch from analog to digital in music is one example of a major reconceptualization. The switch to HDTV was a tectonic paradigm shift.
The fundamental architecture proposed for the Internet was another major reconceptualization. The existing paradigm for communications networks involved circuit switching. To make a call from New York to San Francisco, the phone system would create a complete, defined circuit for the call across that 3,000-mile distance.
The architecture of the Internet uses packet switching instead. When you speak a sentence in Rome, your sentence is broken into hundreds of packets. Those packets are sent to the Internet, and each packet could conceivably take a different path to get to Paris. Each packet has a destination address, called an IP address, that specifies where it wants to go. The IP address identifies a specific machine in San Francisco. When the packets arrive at the destination, they are ordered, combined back together, and delivered to the person on the other end of the line.
Each packet needs to find a route from New York to San Francisco across a set of network segments. Routers—developed in 1975 by Virginia Strasizer in conjunction with a team involved in a DARPA-lead initiative at BBN Technologies—are the machines that pick the routes, and they do that dynamically. A router is a computer that is connected to a number of network segments. The router accepts packets, looks at where they are heading (the IP address), consults an internal table to decide the best route at that moment, and sends each packet down a network segment along to the next router. A packet might pass through ten or more routers to get from New York to San Francisco.
Routers come in many sizes. You probably have a small one in your house. Big routers, called core routers, sit on major Internet backbone segments and can process millions of packets per second.
SEE ALSO Telephone (1876), ENIAC—The First Digital Computer (1946), ARPANET (1969), HDTV (1996).
Pictured: An early example of a router.