The Advanced Research Projects Agency Network (ARPANET) developed by the U.S. Department of Defense was the world's first operational packet switching network, and the progenitor of the global Internet.
Packet switching, now the dominant basis for both data and voice communication worldwide, was a new and important concept in data communications. Previously, data communications was based on the idea of circuit switching, as in the old typical telephone circuit, where a dedicated circuit is tied up for the duration of the call and communication is only possible with the single party on the other end of the circuit.
With packet switching, a system could use one communication link to communicate with more than one machine by assembling data into packets. Not only could the link be shared (much as a single mail person can be used to post letters to different destinations), but each packet could be routed independently of other packets. This was a major advance.
- ARPANET Maps 1967 to 1977
- Looking back at the ARPANET effort
- The Computer History Museum Images of ARPANET from 1964 onwards.
- A Brief History of the Internet
- Paul Baran and the Origins of the Internet
- Leonard Kleinrock's Personal History/Biography
- Personal anecdote of the first message ever sent over the ARPANET
- Len Kleinrock on the Origins (subscribers only)
- Internet Chronology by Larry Roberts
- The Faces in Front of the Monitors
- ARPANET Google Video)