30 years ago today, the modern Internet was born. Vint Cerf writes about it at Google's Blog.
Each network had its own communications protocol using different conventions and formatting standards to send and receive packets, so there was no way to transmit anything between networks.
In an attempt to solve this, Robert Kahn and I developed a new computer communication protocol designed specifically to support connection among different packet-switched networks. We called it TCP, short for “Transmission Control Protocol,” and in 1974 we published a paper about it in IEEE Transactions on Communications: “A Protocol for Packet Network Intercommunication.” Later, to better handle the transmission of real-time data, including voice, we split TCP into two parts, one of which we called “Internet Protocol,” or IP for short. The two protocols combined were nicknamed TCP/IP.
TCP/IP was tested across the three types of networks developed by DARPA, and eventually was anointed as their new standard. In 1981, Jon Postel published a transition plan to migrate the 400 hosts of the ARPANET from the older NCP protocol to TCP/IP, including a deadline of January 1, 1983, after which point all hosts not switched would be cut off.
When the day came, it’s fair to say the main emotion was relief, especially amongst those system administrators racing against the clock. There were no grand celebrations—I can’t even find a photograph. The only visible mementos were the “I survived the TCP/IP switchover” pins proudly worn by those who went through the ordeal!
Yet, with hindsight, it’s obvious it was a momentous occasion. On that day, the operational Internet was born. TCP/IP went on to be embraced as an international standard, and now underpins the entire Internet.
There's more at the link.
I was an occasional user of ARPANET at the time of the switchover. I wonder how many of us back then - if any - foresaw just how ubiquitous the Internet would become? I certainly didn't!