Networking
What really happens when you type a URL
DNS, TCP, TLS, and HTTP collaborate in milliseconds. Separating their responsibilities makes the web stop feeling like magic.
First, find an address
A browser cannot connect to a domain name. It needs an IP address, so it checks a chain of caches and DNS resolvers. Each layer tries to answer quickly without losing authority over the data.
That result only tells the browser where to begin. There is still no conversation between your computer and the server.
A connection and an identity
TCP establishes a reliable channel over a network that can lose or reorder packets. TLS then verifies the server's identity and agrees on how to encrypt the conversation.
Each layer solves a different problem. Together they turn uncertain infrastructure into a channel an application can trust.
Finally, a request
Only then does the browser send an HTTP request. The server responds with headers and content, starting another chain of work: parsing HTML, requesting resources, and drawing pixels. Understanding the web is largely about learning to see these layers separately.