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Arpanet

The Arpanet
Forerunner of Today's Internet

The Proposal
In 1968, the Advanced Research Projects Agency (ARPA) sent out a Request for Quotation (RFQ) to build a network of four Interface Message Processors (IMPs). Many of the large computer and telecommunications organizations didn't even respond--they thought it was impossible.

But at BBN, Frank Heart not only thought such a network was possible, he was sure BBN could build it. Heart assembled a first rate proposal team:

  • Dave Walden, a young programmer with expertise in real-time systems
  • Bernie Cosell, a world-class debugger with a reputation for fixing problems
  • Severo Ornstein, a perfectionist hardware ace
  • Will Crowther, an exceptional programmer who specialized in producing complex, tight code
  • Bob Kahn, the consummate theoretician who understood error-control and the problems associated with sending data over telephone lines

BBN's detailed proposal filled 200 pages, replete with flowcharts, equations, and tables detailing timing, routing, transmission delays, and packet queuing. Although a dozen companies bid on the contract, the BBN team was confident that their proposal would be the best. They were right. Even though much larger and better-known organizations had bid on the contract, ARPA awarded it to BBN in January 1969.

Software
The software team, Crowther, Walden, and Cosell, wrote the code that would reload crashed IMPs, pull packets into the machine, figure out how to route them, and send them on their way. They spent most of the summer devising a routing scheme that would automatically route data packets around troubled links in the network and update itself several times per second.

Hardware
The hardware team worked with an off-the-shelf Honeywell 516 to design the high speed I/O devices that would need to be added to the basic model. Ben Barker, a Harvard-educated hardware engineer and the newest member of the IMP team, tried loading several pieces of code onto the customized 516 when it arrived. It didn't work and neither did anything else. Barker worked 16 hours a day, unwrapping misconnected wires from their pins, figuring out where they should be connected, and then rewrapping the wires on each pin, while Ornstein worked on design corrections, which he then relayed to Honeywell's engineers.

Two weeks before the UCLA installation deadline, the next IMP arrived from Honeywell. The machine incorporated few of the requested modifications. Barker again unwrapped and rewired pins, this time with the advantage of knowing how they should be connected. Within a few days, he activated the IMP's interfaces, but it crashed frequently at random intervals. He had a hunch that the problem lay in the machine's timing chain and designed a fix, but the machine had to be shipped to UCLA the next day, leaving no time to test his solution.

The Network
Barker flew to California with the first IMP to make sure the cargo crew treated it with care. Truett Thach, a technician in BBN's Los Angeles office, met Barker and the IMP at the airport. At UCLA, Barker and Thach attached the cables, powered up the IMP, and crossed their fingers. Instantly, the machine picked up where it had left off in Cambridge. Barker phoned Heart to tell him the good news and that he would be coming home in the morning. Heart asked Barker to hang around for a few days to see if it crashed. It didn't.

On October 1, 1969, the second IMP arrived at SRI and the first characters were transmitted over the new network. The ARPANET was born. When IMPs number three and four were installed at UC Santa Barbara and the University of Utah, IMP installations were beginning to seem routine and there was little fanfare. The network quietly expanded to thirteen sites by January 1971 and twenty-three by April 1972.

Outside of BBN, ARPA, and a small group of researchers, this network that would change the world was virtually unknown until the International Conference on Computer Communication in Washington, DC in October 1972. The ARPANET was the only demonstration and by the time it was over, packet switching skeptics were transformed into believers, and several hundred more people had an inkling of the digital age on the horizon.