How Does the Internet Work?

Most of us use the internet every single day, just as often (if not more) as we use our cars. Even if you’re not a car enthusiast, you’ve probably at least taken a look under the hood of your car on occasion. In contrast, most of us probably haven’t ever been to an internet exchange point or submarine cable landing point, despite making use of them all the time.

While you don’t need to understand all the inner workings of your car to drive it, having a basic knowledge of how it works can be very handy. Likewise, having a basic understanding of how the internet works can help you troubleshoot problems, choose better equipment, and better navigate our online world.

We’re not much help when it comes to cars, but if you want to know more about how the internet works, keep reading.

The internet is a network of networks

On its most basic level, the internet connects computers together. Most of us already connect computers like this on our own home networks, just on a much smaller scale. Your router is the heart of your home network, and it’s the central point through which all your other devices connect. Most home networks are wireless these days, but you can also connect devices to a router with physical cables.

You can connect two computers together directly, but a router makes this easier by acting as a central hub. A router is really just a computer—a specialized computer created to manage the communication between the devices it’s connected to.

By making one connection to the router, it’s like you made a connection to every other computer the router is connected to. This is called a local area network (LAN). If you played a lot of video games in the ’90s, these are the kind of networks that people would set up to have LAN parties in the days before online games were common.

Just like connecting two computers, if you wanted to connect your local network to someone else’s, you could connect your routers together directly. You could also get a bunch of people to connect their local networks to the same router, making a network of networks. This is essentially how the earliest computer networks grew together from several large regional networks into one vast internetworked system that we now call the internet. Today, your home network is part of your internet service provider’s (ISP) network, which is part of the worldwide network that we call the internet.

Information superhighways

The internet of today has grown from its humble beginnings to cover the entire planet. Like your home network, it’s made up of a bunch of physical devices linked together. The bulk of the internet’s infrastructure is made of fiber-optic cables. Because fiber is awesome. Fiber cables beneath the ground span the continent and undersea cables cross entire oceans, allowing near-instantaneous communication around the world.

But who actually builds all this stuff?

How the internet is built

While we’re checking our email and watching Netflix, telecom companies are spending massive amounts of money to build and maintain the routers and cables necessary for the internet to function. Operating and maintaining all the switches, exchanges, and internet backbones that connect regional networks is a huge industry in itself. Our relatively smooth experience of using the internet belies the complicated business deals under the surface that keep the whole thing running.

For example, imagine you want to send an email to your friend in London. You pay your local internet service provider (ISP) to connect to its network. But while it owns the underground cables that connect to your house, it doesn’t own any cables that reach all the way to Europe.

To connect you and its other customers to the rest of the world, your local ISP will have to make a deal with a larger network and pay for transit. That larger network might also have to pay for transit on an even bigger network, or it might have a peering agreement with other big networks—basically agreeing that “You’re free to use my network if I’m free to use yours.”

Thanks to these business deals between telecom companies, your ISP is allowed to pass your data along to larger and larger networks until it reaches an internet backbone that can send it to the East Coast, across the Atlantic, and finally to your friend’s computer in London.

Different kinds of networks at different scales are often grouped into tiers. The biggest networks that form the backbone of the internet are referred to as Network Service Providers (NSPs) or Tier 1 networks. Tier 1 networks are owned by large telecom companies—like AT&T and CenturyLink in the U.S. and Deutsche Telekom in Germany—and are connected to one another through peering agreements. Tier 2 and Tier 3 networks, in contrast, are smaller networks that must purchase transit from larger networks in order to reach the rest of the internet.

Sending and receiving data on the internet

With a globe-spanning network that connects nearly every computer on the planet, how do we actually find anything on the internet? The rules for sending and receiving information across all of these interconnected networks is known as the Internet Protocol (IP).

For this system to work, every device connected to the internet is given an IP address. When a piece of information like a file or an image is sent across the internet, it’s first chopped up into tiny packets of information, each of which is tagged with the IP address of its starting point and its destination, just like a letter being mailed.

Navigating a decentralized network

Perhaps surprisingly, these packets aren’t sent in a straight line to their destination. Since the internet was developed during the Cold War, the U.S. didn’t want a communication system that could be taken out by a precise nuclear strike. Instead, packets are sent out in all directions, so even if a big chunk of the network went down, the information would just find a way around the hole.

This also means that since packets take different paths, they can arrive at their destination in the wrong order. To deal with this, packets also contain additional metadata to put the information back in the correct order and make sure none of it was lost or damaged.

Putting names to online spaces

IP addresses make it possible to find anything on the internet, but they’re not particularly easy to remember. They are also not permanent, so you’d also have to keep track of when addresses are reassigned.

To make it easier to find what you’re looking for, we use domain names like “www.highspeedinternet.com” to stand in for IP addresses. These are also known as Uniform Resource Locators (URLs). When you type a URL into your browser, it sends that name to a Domain Name System (DNS) Server. That server will look up the name and find the IP address you’re trying to find.

Internet vs. World Wide Web

One of the most important services on the internet is the World Wide Web. Although the “internet” and the “web” are often used interchangeably, the internet is the physical infrastructure, while the World Wide Web is an information system that uses the internet.

The World Wide Web is what first made the internet useful for the average person. The Web introduced browsers and web pages, as well as concepts like clickable hyperlinks. This meant that, for the first time, people could spend hours clicking from page to page “surfing” the Web. The first search engines followed soon after, making it easier than ever to find the information you’re looking for.

When you open a web page in your browser, your computer sends a request to a web server that then returns a hypertext document that your browser can display. Many web pages are static, which means that the page is stored on a web server somewhere. When you request to open it, a copy of the page is sent to your computer.

Other web pages are dynamic. When you request to see a dynamic page, the server takes the information you give it and information from its database to construct a web page for you on the fly. This is how Google is able to send you a web page with your search results or how eBay is able to send you a web page with items that are currently on sale.

More than just the Web

Not every server on the internet is a web server. There are lots of different kinds of servers that all have different functions. These include the following:

• Email servers for sending and receiving email
• DNS servers for looking up website names
• File servers for storing data
• IRC servers for old-school internet chat networks
• List servers for managing electronic mailing lists
• Proxy servers for mediating between clients and other servers

There are also many servers on the internet with much more specific functions. For example, you can set up a Minecraft server for the sole purpose of getting your friends together to play.

How the internet gets a website to your home computer

So, now that you know the basics of how the internet works, how does it look when you put it all together? Let’s take a look at what happens when you go to HighSpeedInternet.com.

The first step is opening a browser and typing in the URL. When you hit enter, your computer will send a request to the nearest DNS server to find out the IP address for HighSpeedInternet.com. The DNS server will look it up (or might ask a bigger DNS server if it can’t find the answer) and will send the correct IP back to your computer.

Now that your computer knows which web server it’s looking for, it will send a request to that IP address. That message will go from your computer to your ISP’s nearest router and then bounce from router to router until it gets to the server where our website is hosted. The server then pulls together information from its database to build the web page you requested.

Now that the server has your page, it will break it up into tiny chunks and tag each one with the return address from your original message. The server will then send these packets out to a bunch of nearby routers, which will start bouncing the packets back to your machine.

Once the packets have all arrived, your computer will put them back in the correct order, check to make sure all the information is correct, then display the completed page in your browser. This whole journey back and forth across thousands of miles usually takes less than one second.

The bottom line

The internet is the backbone of modern global communication, transmitting information across a vast, interconnected network of computers. It’s not necessary to understand everything about it, but there are a few important takeaways:

• Everything on the internet exists on a physical server (or servers) somewhere.
• Information is broken up into packets and then reassembled at its destination.
• Packets can take multiple paths through the physical cables of the internet.
• The whole system depends on deals and agreements between huge tech companies that own the physical infrastructure.
• The World Wide Web is the service we most often think of, but there’s a lot more that uses the internet.

By keeping these things in mind, it’s easier to understand important internet news or debates around telecom policy. And it just helps you appreciate how cool the internet is.

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• History of the Internet
• Why Can I Only Get a Few Internet Providers?
• What Is the Difference between Satellite, DSL, Cable, and Fiber Internet?
• What Is Broadband?