How the World Got Wired · The First Message

The IMP

The thing BBN had to build was a special kind of computer. Roberts called it an Interface Message Processor, or IMP for short. (The internet world has always loved its acronyms.)

The IMP’s job was to be the network’s hands and feet. The actual computers at the universities — the big mainframes that scientists used for research — would not talk to each other directly. They were all different brands, different sizes, different shapes, using different software. Trying to teach them all to talk to each other directly would have been an impossible mess.

Instead, every university would get a small IMP standing next to its big computer. The IMP would handle all the network business — chopping messages into packets, sending them across phone lines to other IMPs, receiving packets from other IMPs, putting them back together, and handing the finished message to the big computer next door. The big computers wouldn’t have to know anything about networking at all. They would just talk to their local IMP, and let it deal with everything else.

The IMP was, in other words, the world’s first router. The same kind of device, in spirit, as the little box that probably sits in a corner of your living room right now connecting your home to the internet. The one in your living room is the size of a paperback book. The first IMP was the size of a refrigerator and weighed about 900 pounds. But it did, in essence, the same job.

At BBN, the engineer in charge of designing the IMP was a young man named Bob Kahn. He will have a much larger role in this story later — he is one of the two people you’ll meet in the next chapter who invented the rules the internet still runs on today. For now, you just need to know that Bob Kahn and his small team had less than a year to build something nobody had ever built before, and that almost no one in the rest of the country believed could be built at all.

They built it.

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