A Network of NetworksBack to: A Travel Guide to the Internet
A network is a collection of connections, and they are everywhere! There are human networks of families, friends and communities. There are transportation networks of hightways an railroads. There are utility networks that carry water, electricity and letters from one place to another. And of course there are networks of airwaves and cables that bring sounds and images into our houses.
But the the Internet is is the network to end all networks! This is because it connects millions of other connected groups of computers that create and share information with each other. These computers can be connected by telephone wire, optic cable, microwaves, lasers, or satellites. A network within a building or a campus is called a local area network or LAN. When the network has a span larger than 2 miles, it is called a wide area network or WAN. Most, but not all, of these networks then connect to the Internet. In July of 2002 there were over 125 million host servers on the Internet.Maps can give you an appreciation for the network concentrations in the Internet at the Atlas of CyberspacesThe Military Experiment
The ancestor of the Internet was the ARPANET, a project started by the Department of Defense (DOD) in 1969. In the 1960's the nation feared that a nuclear bomb could destroy our military's computer center and leave America helpless to attack from communist countries. To remedy that weakness, the DOD started an experimental project in which no single central computer ran their computers. Rather, there was a network of computers, each with a portion of the military's information. It ran by dynamic rerouting -- if one of the network links was destroyed, the traffic on it automatically rerouted to another link.
The ARPANET (and it's early version of e-mail) was wildly successful, especially when the large number of universities doing military-funded research were added to the network. Eventually it was broken into two parts: MILNET, which had the military sites, and the new smaller ARPANET, which had the non-military sites. The two networks remained connected, however, thanks to a set of rules called IP (Internet Protocol), which enabled traffic to be routed from one net to another as needed. Today IP is still the language that all Internet networks use to communicate with each other.
ARPANET quickly became overcrowded, so when the National Science Foundation (NSF) needed to connect 5 supercomputing centers, it set up its own regional networks with NSFNET to connect them. In 1987, the NSF opened NSFNET to the U.S. public and U.S. allies. It captured so much of the traffic that in 1990 ARPANET shut down. The NSF allowed independent commercial networks to join the Internet, and eventually the Internet became too large for even the NSF to handle. In 1994 it gave up management to an international voluntary group called the Internet Society. This organization helps the Internet communicate efficiently, but it does not control the type of information sent over the networks. No one controls that!