Table of Contents
Imagine telling your friend to visit your website by saying, “Hey Chomu, go to 192.168.13.21 to check my blog.”
Sounds ridiculous, right?
That’s exactly what the internet would feel like without DNS (Domain Name System). You’d need to remember strings of numbers—called IP addresses—just to visit a website.
But thankfully, we don’t have to do that. We use domain names like google.com, netflix.com, or manrahul.in. DNS is the invisible magic behind translating those human-friendly names into machine-friendly addresses.
Let’s peel back the layers and understand how DNS works under the hood, in a way that even a curious teenager (or a cat named Catoza) could appreciate.
The Internet Before DNS: The Problem
Back in the early days of the internet (think ARPANET), every machine on the network had an IP address, and there was a single HOSTS.TXT file that mapped names to IPs. That file was manually updated and shared across machines. Imagine thousands of people manually editing a shared Excel sheet—disaster waiting to happen.
As the internet grew, this method became completely unsustainable. Enter: DNS, invented in 1983.
What is DNS, Really?
Think of DNS like your phone’s contact list.
You don’t dial your mom’s phone number every time. You just tap “Mom.” DNS works the same way. When you type openai.com in the browser, DNS finds the matching IP address and connects you to the right server.
It’s the internet’s address book — or, more accurately, its phonebook.
How DNS Works (The Journey From URL to IP)
Let’s walk through what happens when Manrahul types manrahul.in in his browser.
1. Browser Cache
The browser first checks if it already knows the IP address (stored in DNS cache). If yes, it skips the lookup.
2. Operating System Cache
If the browser doesn’t know, it asks the OS. The OS checks its own cache.
3. Router/Local Network
Still nothing? The OS asks the router or local DNS server (your home router or office DNS).
4. Recursive DNS Server (Why DNS matters or Google DNS)
Next up, the ISP’s recursive resolver (like 8.8.8.8 if you’re using Google DNS) takes over.
This resolver doesn’t know the answer, but it knows where to find it.
5. Root Name Servers
The resolver starts at the top—the root name server. It asks, “Where can I find .in domains?”
The root server says, “Talk to the .in TLD server.”
6. TLD Name Servers
The TLD server knows where to find manrahul.in. It responds, “Ask the authoritative name server for manrahul.in.”
7. Authoritative Name Server
This is the final answer-holder. It tells the resolver, “manrahul.in lives at IP 203.0.113.15.”
8. Back to the Browser
The resolver returns the IP to your browser. Now your browser makes a request to 203.0.113.15, and boom—the website loads.
All of this happens in milliseconds.
Visual Flow (Helpful Graphic)
Want to visualize this entire process? Check our blog on “How a Website Loads – From Browser Address Bar to HTML“ for a detailed flowchart.
What Are DNS Records?
DNS doesn’t just store A-to-B mappings. It uses different types of DNS Records:
- A Record: Maps domain to IPv4 address
- AAAA Record: Maps domain to IPv6 address
- CNAME: Alias for another domain (e.g.,
www.example.comtoexample.com) - MX Record: Mail exchange info for email delivery
- TXT Record: Extra info (e.g., SPF, verification, etc.)
- NS Record: Nameservers responsible for domain
Each type serves a different purpose in routing or verifying services.
DNS Caching: The Silent Speed Boost
Caching is what makes the internet feel fast. Without it, every visit to Google would trigger a new DNS lookup. Instead, your system stores DNS results temporarily.
But cache has a shelf life, defined by TTL (Time to Live), which tells systems when to refresh the data.
Common DNS Issues
- DNS_PROBE_FINISHED_NXDOMAIN: Domain doesn’t exist.
- DNS server not responding: Could be due to misconfigured network or down DNS service.
- Slow lookups: Sometimes switching to a faster DNS (like Cloudflare
1.1.1.1) helps.
DNS is Not Just for Browsers
DNS is used by:
- Apps (like email clients)
- APIs
- IoT devices
- Servers communicating with each other
Anywhere a hostname is used, DNS is silently doing the translation work.
Under the Hood: Why DNS is Decentralized
The internet is global, and it can’t afford to have a single point of failure. DNS is hierarchical and decentralized:
- 13 root server clusters worldwide
- Thousands of TLD servers
- Millions of authoritative name servers
This architecture ensures reliability and fault tolerance.
Final Thought
Next time you load a website, remember the silent conversation happening in the background—from your browser to root servers, all just to turn a name into an address. It’s the perfect example of how technology makes our lives easier without us even noticing.
Understanding DNS isn’t just for sysadmins. It’s for anyone who wants to truly understand how the web works.
