DNS FUNDAMENTALS

Networking Fundamentals

Learning Outcome

Let's Recall

• Every device on the internet has a unique IP address (e.g., 192.168.1.1)

• IP addresses help computers identify and communicate with each other

• They act as a digital identity for devices

• Data always includes a source IP (sender) and destination IP (receiver)

• Devices use IPs to locate and deliver data accurately

• Without IP addresses, communication wouldn’t be possible

• But IP addresses are hard for humans to remember, especially at scale

Just then, a magical helper appeared — Dina the DNS Fairy​

In a flash, Dina told the computer the number.

Then she said something important:

“Without me (DNS), you would have to remember numbers like:
123.45.67.89 ”

Timmy laughed:
“That’s too hard!”

Transition from Analogy to Technical Concept(Slide 5)

Imagine you want to call your friend using your phone

You don’t usually remember their actual phone number.
Instead, you simply search using their contact name

So in this analogy:

• Contact name → Domain name

• Phone number → IP address

• Phone lookup → DNS resolution

Transition from Analogy to Technical Concept(Slide 5)

Now imagine the internet working in a similar way

Instead of using a simple contact list like your phone, the internet uses a huge network of DNS servers to find IP addresses.

When you enter a domain name, your computer sends a request to these DNS servers asking:

“What is the IP address of this website?”

The DNS servers then work together to find the correct IP address and send it back to your system.

Transition from Analogy to Technical Concept(Slide 5)

Introduction to DNS

What is DNS?

The Internet's Phonebook

DNS stands for Domain Name System. It is the system that translates human names into computer numbers.

We type: Google.com

DNS finds: 142.250.183.14

How DNS Works

How DNS Works (Domain → IP Resolution)

Here’s what happens when you type a URL

• IP comes back → browser loads the website

• You type google.com in browser

• Your system asks a DNS Resolver:

  “Hey, what’s the IP for this?”

• Resolver checks cache (if already known)

• If not found, it goes on a journey:

  • Root Server → “Where is .com?”

  • TLD Server → “Where is google.com?”

  • Authoritative Server → “Here’s the IP”

How DNS Lookup

The DNS Lookup Journey

The Question

You type a URL in your browser.

The Search

The DNS Resolver asks around for the IP.

The Answer

The IP address is found and sent back.

The Load

The browser loads your favorite site!

Component of DNS

The 4 Key Components

Common DNS Types

Common DNS Record Types

Record Type

Full Name

What it does?

A Record

Address Record

Points a domain to an IPv4 address (numbers like 1.2.3.4).

AAAA Record

IPv6 Address

Points a domain to a newer, longer IPv6 address.

MX Record

Mail Exchange

Tells the internet where to send emails for that domain.

CNAME

Canonical Name

Alias record. Points one domain to another domain.

What is a URL

Anatomy of a Web Address

Parts of a URL

Parts of a URL :-

https://www.google.com/search?q=dns#section1

Protocol (https://)

• Defines how data is transferred

Subdomain (www)

• A subdomain is an extension added before the main domain name to organize or separate different parts of a website.

• Different subdomains = different services

Parts of a URL

Domain Name (google.com)

• The human-readable name of the website

• google → name

Top-Level Domain (.com)

• A Top-Level Domain (TLD) is the last part of a domain name, the bit that comes after the final dot.

• In www.google.com → .com is the TLD

• The TLD tells you the category, purpose, or country of a website.

Parts of a URL

Path (/search)

• A path is the part of a URL that comes after the domain and tells the server which specific page or resource you want.

• So here:  /search = Google search page

Query (?q=dns)

• A query is the part of a URL used to send extra information or requests to the server. It usually starts after a question mark ? in the URL.

• Structure: domain.com/path?key=value

•  Starts with "?"

• Used to send data to the server

Parts of a URL

Parameters (q=dns)

• Parameters are the actual pieces of data sent inside a URL query that tell the server exactly what you want.

• They are written in key-value pairs.

Fragment (#section1)

• A fragment is the part of a URL that comes after the hash symbol # and is used to navigate to a specific section within a webpage.

• Structure: https://example.com/page#section1

Parts of a URL

FAQs

• What happens to emails if an MX record is missing ?

-> Without an MX (Mail Exchanger) record, no mail server knows where to deliver emails sent to @yourdomain.com. Emails would fail to route and get lost. MX records are essential for any domain that needs to send or receive email.

FAQs

• What would Happen if DNS did not exist ?

-> Without DNS, you would need to memorize a different numeric IP address for every website you visit. DNS makes the internet usable by letting humans use names while machines continue to use IP addresses behind the scenes.

FAQs

• In what order do DNS servers get contacted during a full resolution?

-> Root Server → TLD Server → Authoritative Server. The Root Server answers 'who handles .com?', the TLD Server answers 'who handles google.com?', and the Authoritative Server gives the actual IP address.

Summary

Which DNS server is the FIRST to receive your query when you type a domain name?

Which DNS server is the FIRST to receive your query when you type a domain name?

C. Authoritative Server

D. Recursive Resolver

If you visit the same website twice, why is the second DNS lookup faster?

If you visit the same website twice, why is the second DNS lookup faster?

C. The TLD server stores your IP

B. The resolver uses its cache

Which part of a URL defines how data is transferred?

Which part of a URL defines how data is transferred?

D. Query string

C. Protocol