ARPANET: The First Network
ARPANET was the first packet-switching network and the direct ancestor of today's internet. Created by ARPA (Advanced Research Projects Agency) in 1969, it proved that computers could communicate without a central hub—and survive a nuclear attack.
The Problem ARPANET Solved
In the 1960s, telephone networks used circuit switching—creating a dedicated physical path between two points for the duration of a call. This was inefficient for computer communication, which comes in bursts. J.C.R. Licklider and Robert Taylor at ARPA envisioned a network where computers could share resources and communicate via packet switching.
Packet Switching: The Key Innovation
Unlike circuit switching, packet switching breaks data into small chunks (packets) that travel independently through the network. Each packet contains its destination address and can take different routes. This made the network robust—if one path failed, packets could be rerouted automatically.
The First Four Nodes
On October 29, 1969, the first message was sent from UCLA to Stanford Research Institute (SRI). The planned message was "LOGIN" but the system crashed after "LO"—resulting in the world's first network transmission being "LO". By the end of the month, four nodes were operational:
- UCLA (Sept 1): UCLA's Sigma 7 host computer
- SRI (Oct 1): Stanford Research Institute's SDS Sigma
- UCSB (Oct 15): University of California Santa Barbara
- University of Utah (Dec): Utah's DEC PDP-10
NCP: The First Network Protocol
ARPANET initially used NCP (Network Control Program) to coordinate communication. NCP was later replaced by TCP/IP in 1983—the event called "Flag Day" that marked the birth of the modern internet.
Email Changes Everything
While ARPANET was designed for terminal-to-terminal communication, Ray Tomlinson's 1971 invention of email transformed it into a communications medium. The @ sign separating user from domain remains one of computing's most enduring innovations.