ARPANET's First Message

At about 10:30 in the evening on 29 October 1969, in room 3420 of Boelter Hall at UCLA, the graduate student Charles Kline was trying to send a message to a different computer at SRI—the Stanford Research Institute—to the north.

He started to type "LOGIN". L. O. Then the SRI host crashed. The message that arrived was "LO".

That is the recorded first transmission of what would become the Internet.

The ARPA Vision

ARPANET was a packet-switched network funded by the US Department of Defense's Advanced Research Projects Agency (ARPA, later DARPA). In 1962, J. C. R. Licklider arrived at ARPA and laid out the conception he called the 'Galactic Network'—geographically distributed computers interconnected into a single virtual space in which data and programs could be shared.

This was heretical at the time. Each early-1960s computer was an island. A program written on one machine did not run on another; transferring data meant either physically carrying a tape or running a dedicated one-to-one circuit.

What turned Licklider's vision into something implementable was packet switching, proposed independently by Paul Baran at RAND and Donald Davies at Britain's NPL. Break data into small packets; each finds its own best path to the destination; if an intermediate node fails, the rest takes another route. The Cold War demand for survivability under nuclear attack pushed the design.

Four Nodes

In September 1969, the first ARPANET node—an IMP (Interface Message Processor, the ancestor of the dedicated router)—was installed at UCLA. SRI followed on 1 October, then UC Santa Barbara in November and the University of Utah in December.

The 29 October test was the first host-to-host communication between UCLA and SRI. Kline transmitted one character at a time, confirming receipt with the SRI operator by telephone.

"L?" "Got it." "O?" "Got it." "Sending G"— at which point the SRI host ran out of memory and crashed.

It came back up an hour later; the full "LOGIN" was transmitted the same evening.

"LO" — An Accidental Prophecy

The two letters that arrived in that first test, "LO", have been retold many times.

"Lo"—the archaic English exclamation. "Lo and behold."

Leonard Kleinrock, the UCLA professor in charge, later recalled that "what we transmitted, accidentally, had a Biblical ring." He had not intended it. But the fact that the first words sent across the network that would reshape the world happened to come out that way is the kind of coincidence that journalists treasure.

From NCP to TCP/IP

ARPANET ran for its first years on a protocol called NCP, the Network Control Program. The replacement protocol—designed in 1974 by Vint Cerf and Bob Kahn to interconnect multiple networks—was TCP/IP.

On 1 January 1983, ARPANET cut over from NCP to TCP/IP in a single day, remembered as 'Flag Day'. The date is often cited as the formal beginning of the network we now call the Internet.

ARPANET itself was decommissioned in 1990, after 21 years and about 400 nodes. By then the focus of interconnection had moved on—first to NSFNET (1985) for academic computing, then commercially (the NSF lifted its commercial-use restriction in 1991).

The "LO" of 29 October 1969 is the start of all of it.