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First ARPANET Message Transmitted

29 October 1969.Networking.Protocol deployed.Date precision, exact.Evidence grade, primary.2 primary sources

Drivers:

Research breakthroughTechnological capabilityInteroperability need

ARPA sought to connect expensive computing resources so researchers could share them remotely. The academic community wanted better ways to collaborate across institutions.

On 29 October 1969, a student at UCLA tried to log into a computer at Stanford, about 350 miles away, using a brand new computer network called ARPANET. The system crashed halfway through typing 'LOGIN', but this was still the first message ever sent over what would become the internet.

First ARPANET Message Transmitted event plate

Structured atlas record showing date, domain, evidence grade, source count, and predecessor and successor links.

Event plate: First ARPANET Message Transmitted Convergence-divergence layout. The central hero card carries the event year, type, title, evidence grade, domain and era band. 0 predecessor cards on the left feed in with red arrows labelled "absorbs". 0 successor cards on the right derive with red arrows labelled "spawns". Key terms below the hero pin the vocabulary the event introduced. EVENT PLATE Source: https://www.rfc-editor.org/rfc/rfc1 1969 - PROTOCOL DEPLOYED First ARPANET MessageTransmitted primary evidence Domain: AI and machine learning Era band: E6 AI-scale systems KEY TERMS - VOCABULARY THE EVENT INTRODUCED ARPANET IMP host-to-host packet network Convergence-divergence: predecessors absorbed, successors spawned Hero card carries year, evidence and domain. 0 predecessors flow in from the left; 0 successors flow out to the right. Key termsbelow pin the vocabulary the event introduced.

Forecasts and counterfactuals stay labelled as opinion in the event data. Source: Computer History Museum.

Before

Despite theoretical work on packet switching, no operational packet-switched computer network existed. Researchers at different institutions could not easily share computing resources or communicate electronically.

What changed

The first host-to-host message was sent over ARPANET from UCLA to Stanford Research Institute. This demonstrated that packet switching worked in practice and marked the beginning of the internet.

How it happened

ARPA (Advanced Research Projects Agency) funded the development of a packet-switched network connecting university research computers. The first Interface Message Processor (IMP) was installed at UCLA on 30 August 1969. On 29 October 1969, Charley Kline at UCLA attempted to log into the SRI computer. The system crashed after transmitting 'LO' (the first two letters of 'LOGIN'), but the connection was successfully re-established.

Outcomes

  • Proved packet switching was viable for computer communication
  • Created first operational packet-switched network
  • Established model for collaborative network development
  • Initiated development of network protocols (NCP, then TCP/IP)

Limitations

  • Initial network connected only four sites
  • Required specialised hardware (IMPs)
  • No security mechanisms
  • Limited to US defence research community

Lessons learnt

  • Practical implementation reveals issues theory cannot predict
  • Government funding can catalyse foundational technology
  • Open collaboration accelerates innovation

Stakeholders and artefacts

Organisations

  • ARPAgovernmentFunding and oversight
  • UCLAacademiaFirst ARPANET node, Network Measurement Center
  • Stanford Research InstituteacademiaSecond ARPANET node, NIC
  • BBNvendorBuilt Interface Message Processors

Individuals

  • Leonard KleinrockPrincipal Investigator, UCLALed Network Measurement Center, supervised first message
  • Charley KlineProgrammer, UCLATransmitted first ARPANET message
  • Larry RobertsProgramme Manager, ARPALed ARPANET development programme

Artefacts

  • Interface Message Processor (IMP)hardwarePacket switch connecting host computers to ARPANET
  • Host-IMP ProtocolprotocolProtocol for communication between hosts and IMPs

Key terms

ARPANETIMPhost-to-hostpacket network

Causality

Preceded by: Invention of Packet Switching.

Made possible: TCP/IP Protocol Suite Specified.

On this course

Read in the path How the Internet Works.

Sources

1Steve Crocker. "RFC 1: Host Software". Network Working Group, 1969-04-07.authoritativewww.rfc-editor.org/rfc/rfc1
2Barry M. Leiner, Vinton G. Cerf, David D. Clark, Robert E. Kahn, Leonard Kleinrock, Daniel C. Lynch, Jon Postel, Larry G. Roberts, Stephen Wolff. "A Brief History of the Internet". Internet Society, 1997.authoritativewww.internetsociety.org/internet/history-internet/brief-history-internet/