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The LAN turns 30, but will it reach 40?

ARCnet idea came to an engineer while he was eating a meatball sandwich

By Lamont Wood
January 31, 2008 12:00 PM ET

Computerworld - LAN technology recently passed a milestone -- it has been around for 30 years, some of them tumultuous. But while the LAN seems ubiquitous now, there are those who think its future may be more troubled than its past.

"Comparing the present environment to our original vision, the temptation is huge to say that we foresaw all this," said Bob Metcalfe, one of the inventors of Ethernet (by far the best-selling LAN protocol) and now a general partner at Polaris Venture Partners in Waltham, Mass. "But I will resist and say, 'Duh, wow, look what happened.'"

Ethernet, he explained, was developed as part of a project at Xerox Corp.'s Palo Alto Research Center (PARC) in the early 1970s that pioneered the idea of desktop personal computers connected to one another and to laser printers. The original network speed was just under 3Mbit/sec., gated by the processor of the Alto computer that PARC developed for the project, he added.

Metcalfe recalled that about 100 nodes were operational by the time a groundbreaking technical paper that he co-wrote describing Ethernet appeared in the July 1976 "Communications of the ACM."

First commercial LAN

But that's where the story gets tumultuous, because the 30-year milestone doesn't refer to the birth of Ethernet but to the first commercial installation of a LAN, which took place in December 1977 at Chase Manhattan Bank in New York. And it was not an Ethernet, but a network called ARC (Attached Resource Computer or, generically, ARCnet) from now-defunct Datapoint Corp. in San Antonio.

ARCnet was a beautiful thing.
Bob Metcalfe, co-inventor of Ethernet

"It was impressive in that it was something that people were not even thinking about doing," said analyst Amy Wohl, head of Wohl Associates Inc. in Merion Station, Pa., recalling her first glimpse of an ARCnet at Datapoint headquarters shortly after the 1977 announcement. "Previously, you needed a dedicated line to get a networking connection, and it was expensive and hard to implement."

Harry Pyle, then at Datapoint and now a principal software design engineer at Microsoft Corp., recalled that Datapoint sold desktop machines running multiple data-entry terminals. Supporting additional terminals required bigger machines, and he recalled eating a meatball sandwich at an Italian restaurant when a field engineer said his customer wanted more terminals immediately -- leading to a train of thought that sparked the development of ARCnet.

"With multiple machines supporting maybe 10 dumb tubes each, all tied to the same disk resources, you could leverage additional small computers instead of just building bigger and bigger computers," he explained. Pyle said that he recalled seeing Metcalfe's Association of Computing Machinery (ACM) article during the development of ARCnet, but assumed it was theoretical.

Original name was 'Internet'

The original internal project name was, of all things, "Internet." But that was considered too frivolous, recalled Gordon Peterson, then a Datapoint software developer and now a custom programmer in Dallas. "They decided they did not want to call it a network, since networks were perceived as complicated, expensive and hard to manage," he added.

"Before we finished developing ARC, we repeatedly thought that it can't be this easy -- what are we overlooking? Why has no one done this yet?" recalled Peterson. "But each time we decided that it is this easy, it will be this neat and that no one had gotten around to doing it yet."

The resulting network ran at 2.5Mbit/sec., although, as with Ethernet, faster versions appeared later. The big difference was that with ARC the nodes used a token-passing scheme to take turns transmitting, while Ethernet used collision detection to handle situations where two nodes transmitted at the same time. Using a collision-detection scheme meant that following a collision, each node would back off for a random number of milliseconds before trying again. "The programmer was pounding on tables saying he would not build randomness into his product," Pyle recalled.



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