How a Browser Loads a Website: DNS, TCP, TLS, HTTP, and Rendering

Summary

An explainer walks through URL parsing, DNS resolution, the TCP handshake, TLS authentication and key exchange, HTTP requests, and browser rendering, with a Docker lab for practicing DNS, HTTP, and TLS.

Key points

• The article outlines the sequence from URL parsing through DNS, TCP, TLS, HTTP, and browser rendering.
• DNS resolves a hostname to an IP address; caching may let a resolver answer without querying the root.
• TCP establishes a connection with a three-way handshake: SYN, SYN-ACK, and ACK.
• TLS uses certificates to authenticate the server and key exchange to establish session keys; the article notes certificates do not directly encrypt all traffic.
• After the secure channel is established, the browser sends an HTTP request and processes returned HTML, CSS, and JavaScript.
• A Docker-based lab is offered for practicing DNS resolution, HTTP requests, and TLS negotiation.