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dns.md

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How does DNS work?

DNS or Domain Name System / Domain Name Servers work a little bit like an address book.

As you enter google.com in your address bar, the browser needs to do some work to be able to access google.com's web server. It needs to find its IP address. The DNS will do a lookup to find the corresponding IP address.

However, as millions of requests are executed at the same time, there is not only 1 DNS server responsible for this lookup.

DNS is more of a distributed system with some levels of hierarchy.

  • Step 1: Root servers: divided in 13 groups. If you ask who is google.com, they won't know but they will know which servers are responsible for .com domains. It finds the IP address for the top-level domain server.

  • Step 2: TLD (Top-level domain) layer. Bunch of server are responsible for .net domains, others for .com domains, etc... These won't have a straight answer about who google.com is but they will have a bunch of IP addresses for servers responsible for google.com and its subdomains.

  • Step 3: Domain name layer. This server will have the IP address of google.com and the browser will now be able to contact google.com's web server using this IP address.