ARPANET, or How the Internet Was Born

Have you ever wondered, how did the Internet begin?
Interesting Engineering

Nowadays we consider the Internet as something constant and in most of cases we can not imagine our every-day-life without it. But how the existence of the global network began? Who started everything?

Arpanet_logical_map,_march_1977[Image Source: Wikimedia]

Before the creation of modern Internet, computers communicated with each other using the so called “circuit switching”, where two network nods create communication channel (circuit) across the network. The classic example of such network is the old analog telephone network. It means that the connection is made between two participants and information could be received between them only if both are online.

Now the Internet is based on a principle called “packet switching”, where all participants of a network transmitted packets – units that contain data of any type. Packets are buffered and queued and it doesn't require all members of the network to be online to receive the packets.

The first network that used packet switching was called ARPANET (Advanced Research Projects Agency Network) and the project was funded by Advanced Research Projects Agency (ARPA, now known as DARPA). In the development process participated a lot of scientists, such as: J. C. R. Licklider, Ivan Sutherland, Bob Taylor, Frank Heart and many others.

ARPANET started operations in 1969 and consisted of four main units called Interface Message Processor (IMP): University of California, L. A. (UCLA), where SDS Sigma 7 was the first computer attached to the network; Augmentation Research Center of the Stanford Research Institute, where the NLS system was created, a very important early hypertext system (with the SDS 940 that ran NLS, named "Genie", being the first host attached); University of California, Santa Barbara (UCSB), where the attached machine was Culler-Fried Interactive Mathematics Center's IBM 360/75; and the Computer Science Department at the University of Utah, where Ivan Sutherland had moved, using a DEC PDP-10 computer.

The first message that was sent through ARPANET

[Image Source: Wikimedia]

In the following years ARPANET has been continuously growing, including more and more IMP's across USA. In 1973 the network went outside America, connecting via satellite link to the Norwegian Seismic Array. In the same year another IMP in London was connected to the network. In 1975 the control over ARPANET was taken by the Defense Communication Agency while ARPA was intended to fund advanced researches. 8 years later, in 1983, the network was divided by the US military, separating military from civil messages which led to the creation of MILNET (Military Network).