Ethernet
In 1972, at Xerox’s laboratories in Palo Alto, Bob Metcalfe and David Boggs worked on connecting computers to laser printers within a building. Their solution, which they named Ethernet, went far beyond this initial requirement by achieving 2.94 megabits per second.
The basic idea was brilliantly simple. All computers share the same cable, like people talking around a table. Before speaking, each listens to ensure nobody else is talking. If two start at the same time, they stop, wait a random moment, then try again. This method, a technique called CSMA/CD, works remarkably well despite its apparent chaos.
The first Ethernet used a 75-ohm coaxial cable. Machines connected through special boxes that detected collisions and electrically isolated each station. It was possible to connect or disconnect a machine without paralyzing the entire network, which represented a considerable advantage over centralized systems. Four years later, Metcalfe and Boggs described their invention in a paper in the “Communications of the ACM”. Ethernet left the laboratory to reach the industrial world. The first installations demonstrated the ability to connect hundreds of machines over more than a kilometer.
Xerox then understood the commercial potential of its creation. In 1980, the company partnered with Intel and Digital Equipment Corporation to transform Ethernet into an open standard. This strategic decision proved successful: freeing the technology from its creator accelerated its adoption. The new specification pushed throughput to 10 megabits per second and adopted 50-ohm coaxial cable. Machine addresses expanded from 8 to 48 bits, ensuring their worldwide uniqueness.
The IEEE took over with its 802.3 committee in the early 1980s. This standardization inscribed Ethernet into the OSI model and made it completely vendor-independent. The CSMA/CD protocol became the MAC sublayer of the data link layer, while physical aspects fell under 802.3 standards.
In 1990, the 802.3i standard abandoned the coaxial bus in favor of twisted pairs and star topology. Gone were the cables snaking through false ceilings; each machine now had its own link to a central hub, making installation and maintenance a breeze. Fast Ethernet arrived in 1995 with its 100 megabits per second, followed three years later by Gigabit Ethernet.
Metcalfe and Boggs made technical choices that endured. Ethernet handles neither priorities nor quality of service, leaving these questions to higher-level protocols. This apparent limitation proved to be a strength because the simplicity of the basic mechanism allowed for all subsequent adaptations. The system’s core remained remarkably stable. The controller monitors the channel and applies CSMA/CD rules. The transceiver interfaces with the physical medium. Frames carry source and destination addresses, a type field to identify the encapsulated protocol, data, and a CRC checksum. This streamlined architecture crossed decades without major modifications.
During the 1990s, switches radically transformed Ethernet’s nature. Instead of a shared channel where everyone listens, the network evolved into a set of point-to-point links. Different conversations could occur simultaneously. Full-duplex mode gradually replaced CSMA/CD, which became less useful with switching.
Why did Ethernet triumph where others failed? First through its low cost, a direct consequence of its simplicity. Then through its ability to evolve: throughput increases, media change, but fundamental principles remain. Finally through its openness, with no manufacturer able to monopolize the network.
The designers validated their choices through experimentation. The experimental Ethernet provided precise measurements showing medium utilization approaching 98% under certain conditions. The binary exponential backoff (BEB) mechanism, an algorithm to limit network load when a collision occurs between two messages, ensures stability under any load. These concrete data guided the development of the industrial standard.
Today, Ethernet carries Voice over IP, connects storage arrays, and powers data centers. Throughput reaches 400 gigabits per second over fiber optics. The technology born to connect a few computers to printers now structures the global internet. The most enduring solutions are not always the most sophisticated.