How's It Work?

by Joe Flower

How can the Internet be so much cheaper than long-distance telephone?


International Copyright 1995 Joe Flower All Rights Reserved
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Most Internet traffic moves over leased telephone lines, whether fiber, cable, or copper. What's different is the way the messages are handled. Telephone systems are built out of two things: lines and switches. If I call Barcelona, the telephone system works out a route for my call, and reserves resources for me all along that route, until I hang up, whether I'm sending a fax, talking, or just listening to my sweetheart think. This is called "circuit-switching."

But if we digitize all the information, and use computers as extremely elaborate (and relatively cheap) switches, then we can do something else: "packet-switching." The computer breaks up my information (whether it's a phone call, a fax, an email, or a compressed video) into little "packets" about 200 bytes (or characters) long, tags them each an address header, and sends them out on the network, sharing space with all the other packets bumping around out there. At each node, the "router" computer reads the address on each packet, and sends it toward the whatever node seems in the right direction, and seems to be least busy. Some packets may take different routes from others. When the packets arrive at their destination, a final computer assembles them in their proper order and produces the message. The result is a highly efficient use of resources.

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