Loading a web page

Here's what happens when you open a laptop, join Wi-Fi and type quackgames.net. Each step uses something from the earlier lessons.

Joining. The laptop connects to the access point (Wi-Fi, layer 2), then asks for settings with DHCP: the router gives it an IP address, says which router to send outside traffic to (the default gateway) and which DNS server to use.

Finding the address. The browser needs an IP address, not a name, so it asks the DNS server "what's the address for quackgames.net?" over UDP port 53. To send even that, the laptop needs the router's MAC address, which it finds by broadcasting an ARP question: "who has 192.168.1.1?"

Connecting. With the server's IP address, the browser opens a TCP connection to port 443 (the handshake), then sets up encryption with TLS, which also checks the server's certificate to prove it really is quackgames.net. Each packet hops router to router across the internet, its TTL going down as it goes.

Asking. Finally the browser sends an HTTP request, GET /, inside the encrypted connection. The server answers with the page's HTML. The browser reads it, finds the pictures, styles and scripts it needs, and asks for those too, often over the same connection. All of this usually takes well under a second.