DNS

1. What is DNS?

DNS (Domain Name System) is the system that translates human-readable domain names like google.com into IP addresses that computers use to communicate.

Think of it like the phonebook of the Internet:

Human
  │
  │  google.com
  ▼
 DNS
  │
  │  142.250.x.x
  ▼
Server

You remember:

google.com

Your computer ultimately needs:

IP address

2. What are DNS Records?

DNS records are instructions/data stored in DNS that tell the Internet what a domain or subdomain should point to or how it should behave.

For example:

example.com       A       192.168.1.10
www.example.com   CNAME   example.com
example.com       MX      mail.example.com

Think:

DNS = phonebook DNS Record = an individual entry in that phonebook

Important DNS records

3. What is DNS Resolution?

DNS resolution is the process of converting a domain name into its corresponding IP address.

For example:

You type:

https://google.com

       ↓

DNS Resolution

       ↓

IP address

       ↓

Browser connects to that IP

       ↓

Website loads

A DNS resolver may use its cache first. If the answer isn't cached, it queries DNS servers to find the authoritative answer.

How DNS Resolution Works?

Suppose you type:

www.example.com

Step 1 — Browser asks DNS Resolver

Browser
   │
   │ "What is the IP of www.example.com?"
   ▼
DNS Resolver

The resolver might already have the answer in its cache.

If not, it continues.

Step 2 — Resolver asks Root Server

DNS Resolver
      │
      ▼
Root DNS Server

The root server essentially says:

"I don't know the IP of www.example.com, but I know which servers handle .com."

Root
 ↓
.com TLD servers

Step 3 — Resolver asks .com TLD Server

DNS Resolver
      │
      ▼
.com TLD Server

The .com server says:

"I don't have the final IP, but I know the authoritative nameserver for example.com."

.com
 ↓
example.com authoritative nameserver

Step 4 — Resolver asks Authoritative DNS Server

DNS Resolver
      │
      ▼
Authoritative DNS Server

This server contains the actual DNS records for the domain.

For example:

www.example.com
        ↓
A Record
        ↓
93.184.216.34

Step 5 — Resolver returns the IP

Authoritative DNS
       │
       │ 93.184.216.34
       ▼
DNS Resolver
       │
       │ 93.184.216.34
       ▼
Browser

The browser can now connect to:

93.184.216.34

and request the website.

The entire process

                 DNS RESOLUTION

Browser
   │
   │ www.example.com
   ▼
DNS Resolver
   │
   ▼
Root Server
   │
   │ "Ask .com"
   ▼
.com TLD Server
   │
   │ "Ask example.com nameserver"
   ▼
Authoritative DNS Server
   │
   │ A Record
   │ 93.184.216.34
   ▼
DNS Resolver
   │
   │ 93.184.216.34
   ▼
Browser
   │
   ▼
Web Server

One thing you should understand clearly

There are different DNS servers involved:

DNS Resolver
     ↓
Root Nameserver
     ↓
TLD Nameserver
     ↓
Authoritative Nameserver

Their jobs are different:

| Server                   | Job                                                 |
| ------------------------ | --------------------------------------------------- |
| **Recursive Resolver**   | Finds the answer for your computer                  |
| **Root Server**          | Points toward the correct TLD                       |
| **TLD Server**           | Points toward the domain's authoritative nameserver |
| **Authoritative Server** | Contains the actual DNS records for the domain      |

What is Anycast DNS?

Anycast DNS means the same DNS IP address is advertised from multiple DNS servers located in different geographic locations.

When you make a DNS query, network routing sends your request to the nearest/best available DNS server, rather than always sending it to one fixed server.

Simple example

Without Anycast:

                 DNS Server
              1.1.1.1 — USA
                   ▲
                   │
India ─────────────┘

With Anycast:

                    ┌── DNS Server — USA
                    │
User ──→ 1.1.1.1 ───┼── DNS Server — India
                    │
                    ├── DNS Server — Europe
                    │
                    └── DNS Server — Singapore

All these servers can advertise:

 1.1.1.1

Your request is routed to an appropriate location.

Why use Anycast DNS?

1. Faster: Your DNS query can reach a nearby server.
2. More reliable: If one DNS location goes down, routing can send traffic elsewhere.
3. Scalable: Many DNS servers can share the same IP address and handle queries.

One-line definition

Anycast DNS = multiple DNS servers in different locations using the same IP address, with Internet routing directing your DNS request to an appropriate server.