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How the Internet Works

The internet feels like magic, but it's really just a very large, very fast game of "pass the note." Let's follow a single request from your device to a server on the other side of the planet — and back.

The internet is a network of networks

The word internet literally comes from inter-network: a connection between networks. Your home Wi-Fi is a small network. Your phone carrier runs a network. A university runs one. The internet is what you get when you link millions of these networks together so any device on one can talk to a device on another.

No single computer "is" the internet, and no one owns the whole thing. It works because everyone agrees to speak the same languages — called protocols.

Everything is just packets

When you load a web page, your data isn't sent as one big blob. It's chopped into small chunks called packets. Each packet carries:

  • a piece of the actual data (the "payload"),
  • the source address (where it came from),
  • the destination address (where it's going), and
  • a sequence number so the pieces can be reassembled in order.

Splitting things into packets means many conversations can share the same cables at once, and if one packet gets lost, only that small piece has to be re-sent.

Think of mailing a thick book by tearing out the pages, numbering them, and sending each in its own envelope. The recipient reassembles the book from the page numbers — even if the envelopes arrive out of order.

The layers: a quick mental model

To keep things manageable, networking is split into layers, where each layer only worries about its own job. A simplified version (the TCP/IP model):

  • Application — the program you use (a browser speaking HTTP).
  • Transport — reliable delivery and ordering (TCP), or fast, best-effort delivery (UDP).
  • Internet — addressing and routing packets across networks (IP).
  • Link — the physical hop to the next device (Wi-Fi, Ethernet).

Each layer wraps the data from the layer above it, like nesting envelopes. The receiving side unwraps them in reverse.

Following a single request

Here's what actually happens when you type example.com and hit Enter:

  1. Name lookup. Your device asks DNS to translate example.com into an IP address, the internet's version of a phone number. (We cover this in What is DNS?)
  2. Connection. Your device opens a TCP connection to that IP address on a specific port (port 443 for secure web traffic).
  3. Routing. Your packets hop from your router to your ISP and across many routers, each one reading the destination address and forwarding the packet one step closer — like a relay of road signs.
  4. Request & response. The server receives your HTTP request, does its work, and sends back packets containing the web page.
  5. Reassembly. Your device puts the packets back in order and your browser renders the page.

All of this usually happens in well under a second.

Where security comes in

Those packets travel across hardware you don't control. That's why encryption matters: HTTPS (HTTP over TLS) scrambles the payload so the routers in the middle can move your packets without being able to read them. The padlock in your browser means the conversation is encrypted and the server proved its identity with a certificate.

Understanding this flow is the foundation of security work: almost every attack and defense lives somewhere along this journey — at the name lookup, the connection, the routing, or the application on either end.

Next up: What is an IP Address? →