1969

History of the Internet

First permanent ARPANET link established between UCLA and SRI

The celebrated two-letter “LO” crash was not this event — the durable UCLA–SRI connection came later, on 21 November 1969.

21 November 1969: the link becomes permanent

The first permanent ARPANET link was put into service on 21 November 1969, between the Interface Message Processors at UCLA in Los Angeles and Stanford Research Institute in Menlo Park, California.

This turned the experimental UCLA–SRI connection, used for the famous October login test, into a firmly established and continuing network link running at 50 kb/s.

Two incompatible mainframes, two IMPs

UCLA's SDS Sigma 7 and SRI's SDS 940 communicated through packet-switching IMPs built by Bolt Beranek and Newman.

Each end of the link used a refrigerator-sized Honeywell-based IMP, an ancestor of the modern router — the arrangement joined two incompatible mainframes by placing a packet-switching minicomputer beside each one.

Which 1969 date is which

Three milestones are often collapsed into one supposed birth of the Internet: 2 September was UCLA host-to-IMP communication, 29 October was the UCLA–SRI host-to-host test, and 21 November was the permanent link.

What existed after 21 November was a durable connection between the network's first two sites rather than only an experimental one, with UCSB and the University of Utah joining shortly afterward to form the four-node network. It was still a single experimental network — not yet the Internet as a network of networks.

Sources

Researched 23 Aug 2026 7 sources 3 audit passes Date corrected

How this was checked

Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →

Date corrected. The research places this at 1969-11-21.