What Is the Internet?

What is the internet? And what is the web?
When you study a lot of different things, sometimes even the stuff you naturally knew starts to get confusing. So this time, I decided to look up what the internet actually is and organize my thoughts.

The Internet#

The internet is a massive system that connects computer networks around the entire world.

According to Wikipedia, the internet is a computer network that uses the TCP/IP communication protocol to exchange information between computers, and it's a "global computer network system" interconnected for communication between networks and devices.

Through the internet, you can visit sites that other people have created. You can send emails, share files, and play games with others.

How can you go from your computer to someone else's website and see all that information?

1. Enter a URL: Type the unique address of the desired website into the web browser's address bar.
2. DNS lookup: The DNS (Domain Name System) server is queried to convert the domain name into an IP address. DNS servers are responsible for matching domain names to IP addresses.
3. TCP connection setup: The web browser uses the server's IP address to establish a TCP (Transmission Control Protocol) connection.
4. HTTP request: The web browser sends an HTTP (Hypertext Transfer Protocol) request message to the server. The HTTP request message contains the address of the requested web page and other information.
5. HTTP response: The server receives the browser's request and sends back an HTTP response message. The HTTP response message contains HTML code, CSS code, JavaScript code, images, etc. for the requested web page. The server finds the information the browser requested and packages it in the HTTP response.
6. Web page display: The web browser interprets the received HTTP response message and displays the web page on screen. HTML code defines the page structure, CSS code defines the design, and JavaScript code implements dynamic functionality.

How is everything connected that lets us go on YouTube to watch fun videos and on Instagram to see people's lives?

1. Internet connection methods: Connect to the internet via wired connections (LAN cables, phone lines, etc.) or wireless connections (Wi-Fi, mobile data, etc.).
2. Internet Service Providers (ISPs): ISPs are companies that provide internet access services. They provide equipment like modems and routers, and offer plans with different speeds and data caps.
3. Web browsers: A web browser is a program that connects to the internet to display websites and process user requests.
   Through a web browser, you type the desired website URL into the address bar, the URL is sent to DNS to get an IP address, then TCP/IP connects you to the web server. Once connected, an HTTP request message is sent to request the website's data, and the web server sends the data back via an HTTP response message. The browser interprets the HTTP response and displays the web page on screen.

In the past, www was placed before the hostname to identify web server addresses. Example: https://www.google.com. But nowadays, servers are configured to be accessible using just the hostname. Also, web browsers automatically add www even if the user doesn't type it.

I learned what the internet is and how connections work, but I was curious about how it's physically connected. The whole world is connected by a massive network, and I wanted to know what exactly connects it.
ISPs play that role, providing infrastructure for both wired and wireless connections. About 99% of all communications use submarine cables to send and receive data. Satellite communication has slower data transmission speeds, so it isn't used as much. Submarine cables use fiber optics to transmit data.
To see how fiber optic cables work, I recommend this YouTube video: Fiber Optic Cables, How Do They Work?

The data transmission process of fiber optic cables consists of three main stages: signal conversion, optical signal transmission, and optical signal reconversion.

1. Signal conversion: Fiber optic cables use light to transmit data. Electrical signals need to be converted to optical signals. This conversion is done through a device called an optical transceiver.
2. Optical signal transmission: The optical signal converted by the transceiver travels through the fiber optic core. It reflects inside the core and travels in the desired direction.
3. Optical signal reconversion: When the optical signal arrives at the receiving device, it's converted back to an electrical signal through an optical transceiver. The converted electrical signal can then be interpreted by computers or other electronic devices as text, images, video, music, etc.

Just because something doesn't do what you planned it to do doesn't mean it's useless.

— Thomas Edison