ARPANET: Definition & History

Instructor: Raymond Blockmon

Raymond has earned a bachelor's degree in computer information systems and a master's degree in organizational leadership.

ARPANET was the first proven concept of sending and receiving information regardless of geographical location in near real time. Developed under U.S. Advanced Research Projects Agency, a Department of Defense agency, ARPANET uses packet-switch technology in order to send and receive data with built-in error correction and package assembly. ARPANET was the first design of what has become known as the Internet today.

ARPANET - the birth of the Internet

Have you ever just sat back and wondered how the Internet came to be? Who created it and was it hard to do? The Internet that we know and love today was developed by the U.S. Advanced Research Projects Agency (ARPA), a U.S. Department of Defense (DoD) agency that was tasked to lead special clandestine projects in order to protect national security. ARPA has since changed its name to the Defense Advanced Research Projects Agency (DARPA) to reflect its relationship with the DoD.

Joseph Carl Robnett Licklider, considered the Johnny Appleseed of of computer technology
J.C.R. Licklider

In 1963, Joseph Carl Robnett Licklider described in a memorandum he wrote of a vision as an 'Intergalactic Computer Network' on how computers can communicate with one another between various distances and share information. Due to the time period that he was living in, it could be said that he was almost ahead of his time. However, with a solid vision and great support, his goal would soon be realized. And, at that very moment, the Internet was in its infancy.

If Licklider was alive now, do you think he would ever imagine his idea would have gotten this very big? Can you imagine our world today without the Internet?

Exactly how does ARPANET work?

Good question! ARPANET used the BBN Report 1822 protocol, which formats the data messages to be used on any computer architecture. By doing so, computer vendors did not have to worry about keeping track of the different communication types with ARPANET. Can you imagine trying to create an Internet where you have to know each and every language of all of the different types of computers out there for it work? I hope not, because without standardization, it would be a nightmare.

ARPANET uses packet-switching technology. Packet-switching means that bits of information can take virtually any route and still end up at its final destination. For example, think about where you live and then think about the different ways to get your local supermarket. You can a take the long route or the short route. You can take back roads, streets or even the highway. There is no real set way to get to your destination, as long as you get there. This is the same concept as packet-switching technology.

IMP, an ARPANET router which processes data with the BBN 1822 protocol
Interface Message Processor (IMP)

In order for ARPANET to pass data, it had to use the 1822 BBN protocol. Using a router called the Interface Message Processor (IMP), the 1822 protocol was used to store and forward these messages to other IMPs until the data arrived at the final destination of a computer. The IMPs use currently existing telecommunication infrastructure, such as telephone lines and cables in our towns and cities. Although IMPs were very large and very slow, it proved that we could now share information regardless of our physical location using ARPANET.

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