What is DNS?

DNS (Domain Name System) is a system and protocol that translate domain names into IP addresses.

In simpler terms: DNS is the "phone book of the internet".

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#Why DNS is needed

Computers on a network do not understand website names, they only work with IP addresses, for example:

142.250.184.206

Such addresses are inconvenient for people to remember, so we use names instead:

• google.com
• github.com
• example.com

DNS links a website's name to its IP address.

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#How DNS works (very simply)

When you type a website address into your browser:

1. The browser asks: "What is the IP address of example.com?"
2. The DNS server looks for the answer
3. The DNS server returns the IP address
4. The browser connects to the server using that IP

DNS does not load the website - it only tells you where to go.

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#Why DNS belongs to networking and the internet

DNS:

• runs automatically every time a site is opened
• is used by browsers, applications, servers
• is the foundation of how the internet works

Without DNS:

• IP addresses would have to be entered manually
• the internet would be extremely inconvenient

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#DNS hierarchy (briefly)

DNS is a distributed system:

• root DNS servers
• domain zone servers (.com, .ua, .org)
• DNS servers for specific domains

Thanks to this, DNS is:

• scalable
• fast
• has no single point of failure

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#What matters for an interview

• DNS is not a single server, but a system of servers
• DNS works on a request -> response basis
• DNS mostly uses UDP, but sometimes TCP
• DNS does not transfer pages or files

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#Real-life example

DNS is like contacts in a phone:

• you pick a name
• the phone substitutes the number
• then you call using that number