You don’t usually try to reach a website using its IP address. You can, but it’s very rare.

You usually use a domain name. Like google.com, or flaviocopes.com.

This is very handy because, for example, I can change the server and company I use to host a website while maintaining the same domain name.

The system that maps domain names to IP addresses is called DNS: Domain Name System.

DNS is a network of servers. Your provider will have its own DNS, and your router is already preconfigured to use it.

You can also choose to use Google’s DNS server, which has the IP address 8.8.8.8.

Those DNS servers will receive requests from your computer and, in turn, will ask their own reference DNS server.

The system is organized like a tree. There is one DNS server at the top, called the root DNS server.

To simplify, it knows the IP addresses of the DNS servers that manage each domain extension, like com, net, org and so on, including the country-specific domain extensions and the new ones like blog, dev or tech.

Those DNS servers know the IP address mappings of all the domains under their extension.

Of course the system is set up to ensure caching, redundancy, and capacity to handle high concurrent requests, but this is the general idea.

Lessons in this unit:

0:	Introduction
1:	What is a URL
2:	What is a port
3:	▶︎ The DNS protocol
4:	The TCP protocol
5:	The UDP protocol