The Foundation: A Resilient Network

The Internet began as a response to Cold War fears. At that time, the United States worried that a nuclear attack could destroy centralized communication systems. If the main hub was taken out, the entire network would collapse. To solve this problem, researchers looked for a way to design a system that could continue working even if parts of it were destroyed. The answer was a decentralized network.

The key idea that made this possible was packet switching. Instead of sending information as one continuous stream, packet switching breaks messages into small packets. Each packet can travel separately across different routes in the network and then be reassembled at the destination. This approach made communication more reliable and flexible, since even if one route failed, the packets could find another path to reach their target.

In 1969, this concept became real with the creation of ARPANET, funded by the U.S. Defense Department’s Advanced Research Projects Agency (ARPA). ARPANET first connected four universities—UCLA, Stanford, UC Santa Barbara, and the University of Utah—and allowed them to share data through packet switching. This was the earliest version of what would eventually become the Internet.

As more networks appeared in the 1970s, another challenge arose: they all used different communication rules, or “languages.” To connect these separate networks, researchers Vint Cerf and Bob Kahn developed the TCP/IP protocol suite. TCP handled breaking information into packets and ensuring their safe arrival, while IP handled the addressing and routing of those packets. In 1983, ARPANET officially adopted TCP/IP, which unified all networks under one common standard.

This shift was the turning point. Once every network spoke the same “language,” they could connect together into a single, global system—the Internet. What began as a Cold War project for secure communication had evolved into a worldwide network that today links billions of people, devices, and services across the globe.

Core Services: Naming and Serving

For the Internet to be usable, it needed two fundamental components: a scalable address book and a model for requesting and providing information. This section delves into the Domain Name System (DNS), which replaced a single text file with a global distributed database, and the client-server model, the architectural paradigm that underpins almost every service on the Internet, from web browsing to email.

The World Wide Web

The Web is the application that brought the Internet to the masses. Conceived by Sir Tim Berners-Lee at CERN to solve an information management problem, it was a masterful synthesis of three core technologies. This section explores that vision and the three pillars—URL, HTTP, and HTML—that created a universal, linked information space.