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It was a unsuccessful message. The programmer, Charley Kline, reached the middle of the word "login" before the program was hung up. It was not a good start.

It would be a few more decades before the Internet began to enter our homes, but its impact is almost incalculable. It has transformed almost every facet of life, and entire human generations are identified around its existence.

Fifty years ago, a graduate student named Charley Kline sat on an ITT teletype terminal and sent the first digital data transmission to Bill Duvall, a scientist sitting on another computer at the Stanford Research Institute (now known as SRI International) across California. It was the beginning of ARPANET, the small network of academic computers that pioneered the Internet.

Its communications link was proof of the viability of the concepts that ultimately allowed the distribution of virtually all the information in the world to anyone with a computer.

Today, everything from our smartphones to any IoT device are connected nodes that descend from the original network that Kline and Duvall tested that day.

Following the successful launch of Soviet Sputnik, the U.S. did not want to lose the technological race and in January 1958, formed the Advanced Research Projects Agency (ARPA) within the Department of Defense to support science, technology, engineering and mathematics STEM at universities in the United States research laboratories.

By the mid-1960s, ARPA had provided funding for large computers used by researchers at universities and research centers across the country. The ARPA officer in charge of funding was Bob Taylor, the key figure in computer history, who later directed Xerox's PARC laboratory. At ARPA, he had realized that all of these computers spoke different languages and could not speak to each other.

At the Pentagon, Taylor's computer scientists explained that all of these research computers had different sets of codes. There was no common language or network protocol by which computers located far away from each other could connect to share content or resources.

That soon changed. Taylor spoke with ARPA director Charles Herzfeld to allocate $1 million for research and development on a new network to connect computers at MIT, UCLA, SRI, and many other sites. Herzfeld got the money from a budget line dedicated to ballistic missiles.

The aim of this new communications network (ARPANET) was to maintain communications despite a possible nuclear war.

ARPA brought Larry Roberts, an old friend of Kleinrock's MIT, to manage the ARPANET project. Roberts turned to the work of British computer scientist Donald Davies and American Paul Baran for the data transport techniques they had invented.

Kleinrock's greatest contribution to ARPANET was something called queue theory. At that time, communication links were analogue lines that could be rented from AT&T. They were circuit-switched lines, meaning that a central switch established a dedicated connection between a sender and a receiver, whether they were two people making a phone call or a terminal connected to a distant central computer. There was a lot of downtime in those circuits when words were not spoken or when bits were not transferred.

Kleinrock thought this was a very inefficient way to establish connections between computers. Queue theory allows data packets from different communication sessions to share links dynamically. While one sequence of packets stops, another unrelated sequence can use the same link. Packets that comprise a communication session (e.g., an email) can reach the recipient using four different routes. If a path was disabled, the network would route packets through a different path.

In this new type of network, the movement of data was not driven by a central switch but by devices at the network nodes. In 1969, these network devices were called IMPs, or "Internet message processors. Each machine was a modified and rugged version of a Honeywell DDP-516 computer that contained specialized hardware for network control. 

The original IMP was delivered to Kleinrock at UCLA on Labor Day in 1969. Today, it stands as a monolith in the corner of Room 3420 of the Boelter Room, where it has been restored to look the same as when it handled the first Internet transmission 50 years ago.

Within weeks of Kline and Duvall's first successful communication, the ARPA network was extended to the computers of UC Santa Barbara and the University of Utah. And ARPANET grew from there to the 1970s and much of the 1980s, connecting more and more government and academic computers. And later the concepts developed in ARPANET would be applied to the Internet we know today.