DNS — What Is It, and Why Do I Need It?

February 9, 2026
A Short History of DNS (Domain Name System)

Before DNS existed, the whole internet used one single file called HOSTS.TXT. It lived on one computer at Stanford. Every night, all other computers downloaded this file to learn new names and numbers. As the internet grew, the file became too big, and updates came too fast. One day, the file broke because two people added the same name in different places. Nothing worked. This small crash showed everyone that the internet needed a better system. So in 1983, Paul Mockapetris created DNS to fix the problem forever.

Internet and DNS

The Internet is a huge network of computers. They all talk to each other using numbers called IP addresses. These numbers are long and hard to remember. People prefer names, not numbers. This is where DNS helps.
When you type a website name, your computer does not know where to go. It must ask a DNS server for the correct number. The DNS server looks up the name, finds the IP address, and returns it. Only then can your computer connect to the right place.
DNS is like a guide. It shows your computer the correct path on the internet. Without DNS, the internet would still exist, but it would be almost impossible to use.

Here is an example of a DNS record:

root@OF:~ # dig scriptlie.com

; <<>> DiG 9.20.18 <<>> scriptlie.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 53602
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;scriptlie.com.                 IN      A

;; ANSWER SECTION:
scriptlie.com.          4406    IN      A       132.148.238.149

;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1) (UDP)
;; WHEN: Mon Feb 09 18:49:47 MST 2026
;; MSG SIZE  rcvd: 58

root@OF:~ #

What does it mean?

scriptlie.com.    Domain name
4406 — TTL (time to live), how long the record stays cached
IN — Internet class
A — IPv4 address record
132.148.238.149 — the real IP address of the server hosting the domain

Authoritative vs. Non‑Authoritative DNS

DNS can give you two kinds of answers. One answer comes from the real source. The other answer comes from a cache. Both work, but they are not the same.

Authoritative DNS

An authoritative DNS server is the official source of records for a domain. It stores the real DNS records. When you get an authoritative answer, it means:

  • The server owns the zone
  • The data is original
  • The answer is final and correct

This is the “source of truth” for a domain.

Non‑Authoritative DNS

A non‑authoritative answer comes from a resolver cache. This means the server does not own the zone. It only remembers the answer from before.

A cached answer is still correct, but:

  • It is not the original
  • It may expire when the TTL runs out
  • It is only stored to make lookups faster

Most everyday DNS lookups are non‑authoritative.

How You Can Tell the Difference

If you see:

;; flags: qr rd ra;

This is non‑authoritative. It came from a resolver.

Why This Matters

When you test DNS changes, always check the authoritative server. It shows the real, updated data. The cache may still show the old record until TTL expires.

Conclusion: A Short Overview of DNS

This was a simple and short overview of DNS. You learned what DNS is, how it works, and why it matters. DNS is a big topic, but you now understand the basics. If you want to go deeper, you can read the official DNS RFC documents. These documents explain every part of DNS in detail, but they are very technical.

Here are the main RFCs:

These are the core rules of how DNS works on the Internet.

If you prefer books instead of RFCs, here are two good options:

Both books explain DNS simply and practically.

DNS looks complicated, but once you understand the basics, everything becomes easier. And now you know enough to read DNS records, test domains, and understand how the internet finds websites.