One of the biggest computing inventions of all time, courtesy of Xerox PARC. //

Although watching TV shows from the 1970s suggests otherwise, the era wasn't completely devoid of all things resembling modern communication systems. Sure, the 50Kbps modems that the ARPANET ran on were the size of refrigerators, and the widely used Bell 103 modems only transferred 300 bits per second. But long-distance digital communication was common enough, relative to the number of computers deployed. Terminals could also be hooked up to mainframe and minicomputers over relatively short distances with simple serial lines or with more complex multidrop systems. This was all well known; what was new in the '70s was the local area network (LAN). But how to connect all these machines? //

A token network's complexity makes it vulnerable to a number of failure modes, but such networks do have the advantage that performance is deterministic; it can be calculated precisely in advance, which is important in certain applications.

But in the end it was Ethernet that won the battle for LAN standardization through a combination of standards body politics and a clever, minimalist—and thus cheap to implement—design. It went on to obliterate the competition by seeking out and assimilating higher bitrate protocols and adding their technological distinctiveness to its own. Decades later, it had become ubiquitous.

If you've ever looked at the network cable protruding from your computer and wondered how Ethernet got started, how it has lasted so long, and how it works, wonder no more: here's the story. //

Other LAN technologies use extensive mechanisms to arbitrate access to the shared communication medium. Not Ethernet. I'm tempted to use the expression "the lunatics run the asylum," but that would be unfair to the clever distributed control mechanism developed at PARC. I'm sure that the mainframe and minicomputer makers of the era thought the asylum analogy wasn't far off, though. //

in their paper from 1976 describing the experimental 3Mbps Ethernet, Bob Metcalfe and David Boggs showed that for packets of 500 bytes and larger, more than 95 percent of the network's capacity is used for successful transmissions, even if 256 computers all continuously have data to transmit. Pretty clever. //

It's hard to believe now, but in the early 1980s, 10Mbps Ethernet was very fast. Think about it: is there any other 30-year-old technology still present in current computers? 300 baud modems? 500 ns memory? Daisy wheel printers? But even today, 10Mbps is not an entirely unusable speed, and it's still part of the 10/100/1000Mbps Ethernet interfaces in our computers. //

It's truly mindboggling that Ethernet managed to survive 30 years in production, increasing its speed by no less than four orders of magnitude. This means that a 100GE system sends an entire packet (well, if it's 1212 bytes long) in the time that the original 10Mbps Ethernet sends a single bit. In those 30 years, all aspects of Ethernet were changed: its MAC procedure, the bit encoding, the wiring... only the packet format has remained the same—which ironically is the part of the IEEE standard that's widely ignored in favor of the slightly different DIX 2.0 standard.