Karthik Kadambi

DNS Explained

How Domain Names Convert to IP Addresses

Every website on the internet is hosted on a server that has an IP address. Humans are not good at remembering long numbers. So the internet uses DNS, also called the Domain Name System. DNS converts human-readable names into machine-friendly IP addresses.

When you type google.com or youtube.com, DNS finds the correct IP address and sends it back to your device. Without DNS, the internet would not be usable.

This article explains DNS in a simple and practical way, from domain names to DNS servers to the entire lookup process.

What Is DNS

DNS stands for Domain Name System. It is a global directory system that maps domain names to IP addresses.

Example:

DNS is the internet's phonebook. It makes it possible to use names instead of numbers.

Without domain names, we would need to type IP addresses like 142.250.72.14 or 2607:f8b0:4007:80a::200e into browsers every time we want to visit a website.

Why DNS Exists

Humans prefer names. Computers prefer numbers.

Imagine remembering:

It is impossible for daily use.

DNS solves this problem by:

DNS makes the web convenient and user-friendly.

How a Domain Name Works

A domain name is split into levels.

Example: www.example.com

The full name is read from right to left, starting with the top-level domain.

Types of DNS Servers

DNS is not a single server. It is a hierarchy of multiple server types.

1. Root DNS Servers

2. TLD Servers

They manage domains based on extension.

Examples:

They know where the authoritative servers for each domain are located.

3. Authoritative DNS Servers

These hold the actual DNS records for a specific domain.

Example: If you own example.com, the authoritative server stores your site's IP address.

4. Recursive Resolver

This is the DNS server your device talks to first. It might be your ISP DNS, or public DNS like:

Recursive resolver does the full lookup on your behalf.

DNS Records Explained

DNS stores information using records. Different records serve different purposes.

A Record: Maps a domain name to an IPv4 address.

AAAA Record: Maps a domain name to an IPv6 address.

CNAME: Alias record. Points one domain to another domain.

MX Record: Mail exchange record. Defines mail server for the domain.

TXT Record: Stores plain text. Used for verification and authentication.

You do not need all records now. Start with A, AAAA, and CNAME.

How DNS Lookup Works: Step by Step

Here is the exact flow when you type a domain name.

Let us use www.example.com as an example.

Step 1. Your browser checks local cache: If it was visited recently, the answer is returned instantly.

Step 2. Your device asks the recursive DNS resolver: This is usually your router or ISP DNS.

Step 3. Resolver checks its cache: If cached, it returns the IP quickly. If not, the resolver performs a full lookup.

Step 4. Resolver asks a Root Server: The root server does not know the IP. It tells the resolver: go ask the .com TLD server.

Step 5. Resolver asks the TLD Server: The TLD server does not know the IP. It tells the resolver: go ask the authoritative server for example.com.

Step 6. Resolver asks the Authoritative Server: The authoritative server gives the actual IP address.

Step 7. Resolver returns the IP to your device: Your device uses this IP to contact the website.

Step 8. Browser connects directly to the server: The DNS process is finished. Your device now knows exactly where to send packets.

This entire flow usually takes a few milliseconds.

DNS Caching: Why Websites Load Faster the Second Time

DNS results are stored temporarily for faster performance. Caching happens in multiple places:

Caching reduces lookup time and reduces DNS traffic.

TTL (Time To Live) controls how long DNS results stay in cache.

This is why websites load faster after the first visit. Once the IP is found, DNS stores the result for a short time to avoid repeating the entire lookup.

Dynamic IP Changes Do Not Break Websites

A website can change its server IP address without affecting users. Only the DNS record needs to be updated.

Example:

  1. A website originally points to 192.0.2.10
  2. The server migrates to a new IP 198.51.100.50
  3. The DNS A record is updated to the new IP
  4. Users still type the same domain name
  5. DNS now returns the new IP address

This makes domain names extremely flexible and allows websites to move between servers, data centers, or cloud providers without users noticing any change.

What Happens if DNS Fails

If DNS stops working:

The internet becomes unreachable even though the physical network works. This shows how important DNS is.

DNS over HTTPS and DNS over TLS

Modern DNS supports encryption.

DNS over HTTPS (DoH): Sends DNS queries inside HTTPS to prevent spying.

DNS over TLS (DoT): Encrypts DNS traffic at a lower level.

Benefits:

Services like Cloudflare and Google provide encrypted DNS.

Real-World Example of DNS Lookup

Let us say you visit youtube.com.

  1. Browser checks cache
  2. Device asks resolver
  3. Resolver asks root
  4. Root redirects to .com TLD
  5. TLD redirects to Google's authoritative server
  6. Resolver gets A record with IP
  7. Resolver returns the IP to your device
  8. Your browser connects to the YouTube server

Every website works this way.

Conclusion

DNS is the naming system of the internet. It converts human-friendly domain names into machine-friendly IP addresses. DNS uses a hierarchy of servers, caching, and efficient lookup processes to make browsing fast and reliable.

Without DNS, the web would be a complex network of IPs that humans cannot remember. DNS makes the internet accessible and user-friendly.

You now understand:

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