What is DNS?

DNS (Domain Name System) is an application-layer service and protocol that translates human-readable domain names into IP addresses.

In short: 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).

But it is inconvenient for people to remember those, so we use names instead:

• google.com
• wikipedia.org
• example.com

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

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#How DNS works (simplified)

When you enter a site's address in a browser:

1. The browser asks: "What is the IP address of example.com?"
2. The DNS server looks up the match
3. The DNS server replies: "The IP address is such-and-such"
4. The browser then connects to the server by IP

Without DNS, the internet as we know it would not work.

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#An important point for interviews

DNS does not load websites and does not transfer pages. It only reports the IP address of where to go next.

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#DNS hierarchy (briefly)

DNS is organized as a hierarchy:

• root DNS servers
• top-level domain servers (.com, .org)
• servers for specific domains

This lets DNS:

• be distributed
• work fast
• have no single point of failure

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#What data DNS stores

DNS can store:

• a site's IP address
• mail server addresses
• service information about a domain

The most important and most commonly asked about: domain → IP address

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#A real-life example

DNS is like the contacts on your phone:

• you look up a person's name
• the phone shows the number
• then you call that number

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#Short answer for the interview

A ready-made phrasing:

DNS is an application-layer system and protocol designed to translate domain names into IP addresses, so a client can find the right server on the network.