ARPANET: The Project That Launched the Internet

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The internet is (almost) everywhere. We rely on it when we want to buy a new phone or a computer and use it when we need help with studying. It’s a great place to play games, share music, or maybe even meet the love of your life. But it wasn’t always like this. 

You’ll often hear that the internet began in the ‘90s, but its actual beginnings date back way earlier. To be precise, it was envisioned by a scientist who wanted to improve communication between computers and humans and how they exchange data.

That is how the Advanced Research Projects Agency Network (ARPANET for short) came to life. So, what is ARPANET?  This article will guide you through its beginnings, definition, use cases, and the influence it’s had on our lives.

The Definition of ARPANET

ARPANET’s main task was to provide a faster, more secure flow of information from one place to another and protect systems from possible attack. Although we may think that its creators didn’t expect it to turn into what it is today, some of their predictions were actually pretty accurate.

ARPANET was the first network that successfully connected more than two computers. If we want to provide a brief but exact ARPANET definition, we could say it was a network that connected several research centers and universities using packet switching. It was funded by the Advanced Research Project Agency, which was a part of the United States Defense Department. ARPANET formed the basis for the internet as we know it today.

The Beginnings of ARPANET

Although many believe that ARPANET was created and used only for military purposes, it was mainly researchers and scholars who benefited from it. But why was ARPANET created? Simply put, there was a need for a faster and easier flow of information across long distances and multiple computers. The main goal was to create a network without computers being connected to dedicated phones

The key figure in creating ARPANET was JCR Licklider, who penned the “Intergalactic Computer Network” memo. Addressing his colleagues, he shared his vision of everyone being able to access a shared computer network globally, and he later became one of the people who invented ARPANET. Luckily, this idea was received well, as the American government wanted to protect its networks in case of a nuclear attack during the Cold War. This way, even if the computers got destroyed, data would be stored on the network and could be transferred from one device to another.

In 1962, Licklider became the director of the Advanced Research Projects Agency (ARPA). During his tenure, this department recorded groundbreaking results. He was responsible for the demilitarization of ARPA and strongly advocated for pairing computers with humans to achieve greatness. 

So, when was ARPANET established? Specifically, the project was initiated in 1966, and in October 1969, the first communications were established via this system. Most sources cite 1969 as the year it began in earnest.

The first message was supposed to be “login,” but the system crashed, managing only to send “lo.” The message was sent from UCLA to the Stanford Research Institute. By the end of the year, the University of Utah, the University of California, and Santa Barbara had joined the network. Although the first message was not fully delivered, the ARPANET computer successfully sent the message on its second attempt.

Another notable figure who helped develop ARPANET was Leonard Kleinrock, who invented packet switching, one of the technologies on which the internet is based. In the 1970s, Cerf and Kahn invented the TCP/IP protocol, and Ray Tomlinson came up with network email. Thanks to these contributions, we were able to write this article, and you can read it. 

How ARPANET Worked

Even though this network would probably not impress many contemporary users of the internet, ARPANET was revolutionary for its time. 

It worked by connecting nodes on a network from different places, a connection that was initially made possible by the NLS system. The system used the 1822 protocol to format data messages that could be used on different computers. Because of that, vendors did not have to deal with various computer languages when using ARPANET. 

This technology also used packet switching to send chunks of information to a destination, but not necessarily using the same path. We’ll discuss that in more detail later in this article. 

Looking at the history of ARPANET, we can see that some of its features were critical for the future of our civilization. The technologies that brought ARPANET to life were the TCP/IP protocol, interface message processors (IMPs), and packet-switched networks. 

TCP/IP Protocol

The Transmission Control Protocol/Internet Protocol was used to provide connectivity for ARPANET computers. Even today, this standard is used to connect computers to the internet. The key benefit was that all the computers used a singular computer language. This is one of the reasons why ARPANET is considered the forerunner to the internet. 

Packet-Switched Networks

This technology made it possible for information to arrive quickly at a destination. It works by breaking down a piece of information into small chunks, which later arrive at the same destination but not always via the same route. 

Interface Message Processors

IMPs were a key component of ARPANET’s early technological foundation; they were essentially the forerunners to routers. They worked independently of one another and could be used by any computer with the right settings. 

ARPANET Computers

Before ARPANET was introduced, computer systems consisted of huge machines that would take up entire rooms, and they could pass on information only through one path. The typical ARPANET computer was much smaller, although still huge compared to modern computers

The idea behind ARPANET was to connect multiple computers across the country, but its beginnings were pretty humble. There were four computers in four different locations connected via a phone line and IMPs

The four computers were UCLA’s SDS Sigma 7, Stanford’s SDS-90 Computer, the University of California’s IBM 360/75, and the University of Utah’s DEC PDP-10.  The operating systems these computers used were, respectively, Sigma Experimental OS, Genie OS, OS/MVT, and Tenex. 


ARPANET was extremely useful, as it allowed researchers and scholars to store and exchange information via computers across different locations. While it didn’t exactly work like the internet, ARPANET made an enormous difference.

It provided better communication between non-profit, governmental, and military computers. Later on, it expanded to include nodes outside of the United States. ARPANET improved the secure sharing of information within educational, administrative, and security domains. Indeed, the best use case we’ve seen from ARPANET has been the emergence of the internet itself. 

By 1981, ARPANET’s network of nodes included 213 connections, and in 1984 the military got its own network called MILNET

One of the first and most important applications of the ARPANET was connecting multiple computers in a primarily closed circle, which changed over time. 

The Fall of ARPANET and the Rise of the Internet

Before ARPANET was decommissioned in 1990, it contributed massively to research and education in various fields. As technologies evolved, The National Science Foundation Network replaced ARPANET, and the era of the internet began. 

The amount of data transferred through the internet was minimal during the first phases of its popularization in 1992. Still, its traffic was growing with each passing day. 

None of this would be possible without the foundation the original ARPANET laid; we wouldn’t have been able to write this article and you wouldn’t have been able to read it.

Since Tim Berners-Lee created the World Wide Web in 1989, the internet’s development has only gotten faster and faster. Today, social media is used by nearly half of the world’s population. We can use the internet for everything from streaming our favorite movies to purchasing any items we need. And while there are downsides like new cyber threats emerging all the time, it’s clear that the internet has had a net positive impact on many people’s lives.


Taking a closer look at ARPANET’s history enables us to better understand how certain modern technologies work today. From the idea that there needed to be a network that could save critical data in case of a nuclear attack, the creators of ARPANET provided us with so much more.

This technology has been a game-changer. Even though it took a few decades for ARPANET to fully transform into the internet, humanity should be forever thankful to the pioneers who paved the way for a better life and more efficient business transactions. From managing to connect several computers during the past century, we’ve reached a point where we’re able to schedule doctor’s appointments online, video chat with friends 5,000 miles away, and even use face recognition software to unlock our phones and laptops. 

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