From Wi-Fi to Web Page - Understanding Internet Connections Through a Letter Relay

You connect to Wi-Fi and open a website on your phone or computer. It's something you do every day without thinking, but have you ever wondered what happens between tapping a link and seeing the page on your screen? As it turns out, data travels from your phone to a faraway server like a letter being passed along in a relay.

The moment you type a URL into your browser and tap "Go," your phone sends a request (think of it as a letter) to the Wi-Fi router using radio waves. The Wi-Fi router is like a small post office inside your home. It collects letters from the devices in your house - phones, computers, game consoles - and forwards them to the next stop.

Wi-Fi signals have a limited range. Walls and floors weaken the signal, so the farther you are from the router, the slower or more unstable your connection gets. If videos keep buffering in the bathroom, it may be because walls and water weaken the signal.

The router sends the letter through a line such as a fiber optic cable to your Internet Service Provider (ISP). The ISP is like a big regional post office that handles letters from tons of homes and businesses, then sends them out onto the internet highway.

In Japan, there are telecommunications groups such as NTT, KDDI, and SoftBank, each with networks spanning the country. The stretch from your home router to the ISP is sometimes called the "last mile."

If the website's server is in another country, your data travels through undersea cables that cross the Pacific or Atlantic Ocean. These cables are bundles of fiber optics laid on the ocean floor - just a few centimeters thick - carrying light signals at incredible speed. Data can travel from Japan to the west coast of the United States in a short time. According to the TeleGeography FAQ, over 1.5 million kilometers of undersea cables are laid across the world's oceans, and most international communications are said to pass through them. You might picture satellites doing this job, but it's actually cables on the ocean floor that handle most of the heavy lifting.

Once the request reaches the server, it looks at the URL and figures out which page you want. Then it sends back the HTML, images, and other data as a reply letter. That reply travels back through the undersea cables and ISP, arrives at your Wi-Fi router, and finally shows up as a web page on your phone screen.

Here's where the role of the URL is important. The URL is the address on the letter. If the address is wrong, the letter won't arrive. If the letter reaches the server but there is no page at that address, it comes back as "undeliverable" - that's a 404 error. Shortening a long URL into a short link makes it harder to get the address wrong and makes sharing easier.

When you browse the internet without Wi-Fi, you're using 4G or 5G mobile data. The overall process is the same, but the first leg of the journey is different. With Wi-Fi, your phone sends signals to a router. With mobile data, your phone sends signals to a cell tower. Cell towers are installed on poles and rooftops around town, and from there the data connects to the ISP's network.

Wi-Fi works in limited areas like your home or a cafe but lets you use data without worrying about the amount, while mobile data works anywhere but some plans come with a monthly data limit. If you're watching a lot of videos, one option is to use Wi-Fi.

Free Wi-Fi at cafes and train stations is convenient, but the connection might not be encrypted. Without encryption, other people on the same Wi-Fi could potentially peek at your data. When using public Wi-Fi, one way is to check whether a website's URL starts with "https://" - the "s" stands for "secure," meaning the connection is encrypted.

Also, watch out for the login page that pops up when you connect to public Wi-Fi. Fake Wi-Fi hotspots are sometimes set up to steal personal information. Not connecting carelessly to a network you don't recognize helps you avoid these tricks.

Between connecting to Wi-Fi and seeing a web page, your data takes a long journey: phone, router, ISP, undersea cables, and finally the server. The URL is the destination address for that journey, and without the right address, the page won't load. When you think about data racing around the world every time you open a web page, it's kind of exciting, isn't it?