ALOHAnet
lorenetworking
The 1971 University of Hawaii radio network whose random-access scheme became the ancestor of Ethernet's collision handling.
Norman Abramson's team needed to link campuses across islands, so ALOHAnet let stations transmit whenever they had data and simply retransmit after collisions. That 'try, collide, back off' idea is the direct intellectual ancestor of Ethernet's CSMA/CD: Robert Metcalfe studied ALOHA closely before sketching Ethernet at Xerox PARC. Wireless networking, in a sense, came before wired LANs.
ALOHAnet, built at the University of Hawaii in 1971, connected computers across islands using radio rather than cable, and had to solve a problem wired networks could avoid: many stations sharing one channel with no way to coordinate who transmits.
Its answer was radical and worked. Stations transmit whenever they have something to send, detect collisions by the absence of an acknowledgement, wait a random interval, and retry. The randomness is the whole trick, since two stations that collide and then retry after fixed delays will collide again forever. Slotted ALOHA improved efficiency by aligning transmissions to time boundaries, roughly doubling throughput.
That mechanism is the direct ancestor of Ethernet. Metcalfe cited ALOHAnet explicitly, and carrier sense multiple access with collision detection is ALOHA plus listening before transmitting. Modern Wi-Fi uses collision avoidance rather than detection, because a radio cannot easily listen while transmitting, but the random backoff is the same idea. A network built to cross water between islands produced the contention algorithm underneath most local networking since.