From telegraph to internet — the history of data communication

The craft of data and communication is about moving information between machines. But the desire to send messages faster than a person can travel is much older than the computer. History begins in the 1800s, when people first learned to send information over long distances with electricity — and it leads in a straight line to the network you debug today.

§The telegraph — the first electric message

Before there were computers, there was the telegraph. From the mid-1800s you could send messages as short and long electrical impulses — dots and dashes in Morse code — through a copper wire. It was a revolution: a message that before took days to send by horse or ship could now arrive in minutes. In 1858 the first transatlantic telegraph cable was laid between Europe and North America, and the world shrank in one blow. The telegraph taught us the basic idea that the whole trade is built on: information can be coded into signals, sent over a wire, and decoded again at the other end.

§The phone and line coupling

Where the telegraph sent messages as signs, the telephone made it possible to send the voice itself as an electrical signal. The telephone network grew at the end of the 1800s and was for over a hundred years built on a technique called line switching (circuit switching): when you called, a fixed connection was reserved all the way through, and it was busy as long as the conversation lasted. It worked fine for speech, but it turned out to be a bad idea for data — and this is precisely where one of the major shifts in the field's history lies.

§Computers should talk to each other — packet coupling arises

In the 1950s and 60s large mainframe computers stood isolated each on its own. Researchers wanted to share computing power and data between machines at different universities but line connection from the telephone world fit poorly: it was wasteful to lock an entire line while two computers only exchanged data in brief bursts. The solution became packet switching: data is cut into small packets that each find their way through the network and are reassembled at the other end. Many senders can share the same wires and if one path fails packets can take another. That is still how the internet works today.

In 1969 the first packet-switched network ARPANET was put into use in the USA funded by the American Department of Defense research agency. The first messages went between just a few university computers. It was the tentative attempt that would grow into the internet.

§TCP/IP — a common language binds networks together

A problem quickly emerged: several different networks arose that could not communicate. In the early 1970s Vinton Cerf and Bob Kahn devised a common protocol that could function as a bridge between networks — it became TCP/IP. The idea is simple and brilliant: each network can function in its own way internally as long as the packets are wrapped in a common format when they move on. On January 1 1983 ARPANET officially switched to TCP/IP and that date is often considered the internet's birthday. Shortly after came the domain name system (DNS) which let us use readable names instead of numbers.

§Local network, World Wide Web and home are connected

While the internet grew between institutions, computers were also linked together locally. Ethernet, which Robert Metcalfe developed in the early 1970s at Xerox PARC, became the dominant way to connect machines in an office — and the RJ45 connector cable and switch are still everyday equipment. In 1989, Tim Berners-Lee proposed the World Wide Web, and when it was opened to the public in the early 1990s, it transformed the internet from a tool for researchers to something for everyone. With modems, then broadband and fibre, the internet entered homes.

§Wireless, mobile and the cloud

The next major shift was cutting the cord. The first Wi-Fi standard came in the late 1990s and made wireless local networks everyday. At the same time mobile networks grew from voice to data so the internet came in the pocket. In recent decades much of what used to stand as physical servers in a room has moved to data centers — what we call the cloud — and virtualization has made it possible to run many servers on the same hardware. The trade has moved from pulling cables to equally managing securing and monitoring services you can't touch.

§Timeline — the major shift in data communications

§What the story teaches a technician

Data communications is one of the youngest trades, but it stands on the shoulders of telegraphists, telephone technicians and the researchers who invented packet switching. What has changed is the speed, the volume and the wireless — but the basic idea is the same as in 1858: information is encoded, sent over a link and decoded again. If you understand where the ideas come from, you can better see why today's networks are built the way they are — and why concepts such as layers, protocols and addresses are here to stay.

“Every time you plug a patch cable into a switch, you continue a wire that was spun with the first telegraph cable.”

— Professional view on the roots of data communication.