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Happy 50th Birthday to ARPANET, Progenitor of the Internet

Dominique Adams


Geek Birthday Cake

Today is the 50th anniversary of the first-ever transmission made across the Advanced Research Projects Agency Network, aka ARPANET, the forerunner of the internet.

On 29th October 1969, the first message was sent via the Advanced Research Projects Agency Network (ARPANET) by a UCLA student programmer, Charlie Kline.

Supervised by UCLA computer science Professor Leonard Kleinrock, Kline used the University’s SDS Sigma 7 computer to login to an SDS 940 computer at Stanford Research Institute. The historic message was composed of one word, “login”, however the first message dropped after Kline had typed “lo”.

This marked the first connection on a wide area network using a new technology called packet switching.

After establishing the connection, Kline was able to sign into an account on the SRI computer and start running programs, using the system resources of a computer 350 miles away. Another month would pass before the first permanent ARPANET link was established.

The success of this transmission was proof of the feasibility of the concepts that eventually enabled the distribution of virtually all the world’s information to anybody with a computer. This lay the foundations for the world wide web as we know it today.

First conceptualised in the 1950s, ARPANET was born out of a need to connect the limited number of large powerful research computers and researchers, who were often separated by geographical distances. The researchers needed a reliable way to switch nodes and network links and ARPANET was that solution.


ARPANET first started as a project under the Advanced Research Projects Agency (ARPA now known as Defense Advanced Research Projects Agency, or DARPA), which was part of the US Department of Defense. With the Cold War underway, the Air Force was seeking to harden its radar system to survive a nuclear attack and be able to respond. Kleinrock has previously said that ARPANET was, in a sense, a child of the Cold War.

ARPA IT head Bob Taylor persuaded director Charles Herzfeld to fund the project based on the recently invented packet switching networking protocol. The goal behind it was to connect various computers together instead of having mainframes try to connect to other mainframes directly.

Rather than relying on circuit switching to transfer data, ARPANET would send small “packets” of information across various paths of interconnected interface message processors, which would be known as nodes, with that information being reconstructed once it gets to its destination.

The descendants of these nodes are present in most of the technology we own today, from smartphones to automatic garage doors.

Initially, the ARPANET network connected only two computers, but this grew to four interface message processors, and then throughout the 1970s more university nodes were incorporated to the network, growing to 57 in 1975 and then 213 in 1981. By 1984 the number of nodes had passed 1,000.

Compatibility issues, which became more apparent as more computer connected to the network, were resolved by the development of Transfer Control Protocol/Internet Protocol (TCP/IP), which was introduced as the standard networking software stack in the ARPANET.

The ARPANET project was officially taken out of service in 1990 after partnerships with the telecommunication industry paved the way of future commercialisation of a new world-wide network, known as the Internet. By then ARPANET had already made a world-wide impact and would continue to do so over the coming decades.

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Dominique Adams

Staff Writer, DIGIT

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