📑 Table of Contents

• What is the Internet?
• How is data transferred?
• Communication in Internet use
• IP Address Concepts
• Internet Protocol (IP)
• DNS (Domain Name System)
• DNS Working Steps
• In-depth DNS Working
• MAC Address
• Port Numbers
• Common Ports
• HTTP vs HTTPS
• IP Technical Details
• Networking Infrastructure
• Security Concepts

What is the Internet?

Internet ek global network of networks hai jo duniya ke crore devices, computers aur servers ko connect karta hai taaki wo data share aur communicate kar saken.

How is data transferred?

Data ko chhote-2 packets me tod diya jata hai.

Packets → routers aur servers ke through ghoomte hue destination tak pahuchte hain.

Destination par → wo packets dobara jod kar original data ban jaate hain.

Communication in Internet use

• Email (digital letter)
• Chats/Calls (WhatsApp, Zoom)
• Social Media (Instagram, YouTube)
• Banking, Education, Shopping – sab kuch internet se communicate karta hai.

IP Address Concepts

IP Address ek unique number hota hai jo har device ko diya jata hai taaki usko network/internet par identify kiya ja sake.

example - Ghar ka address jaha courier pahuchta hai.

Internet Protocol (IP)

IP = Internet Protocol

IP Address Format

• IPv4 → 32-bit (e.g., 192.168.1.1)
• IPv6 → 128-bit (e.g., 2001:0db8::7334)

IP Address assign

• Global → IANA / RIRs
• Local → ISP (Jio, Airtel, BSNL)

ISP की Role

ISP tumhe internet connection + IP address provide karta hai.

Dynamic IP

Har baar internet connect karne par naya IP milta hai.

Advantage → Security aur efficient use of IP addresses.

DNS (Domain Name System)

DNS = Internet ka Phonebook.

Ye domain name (google.com) ko IP address me convert karta hai (142.250.190.14).

DNS Working Steps

• User type karta hai → www.google.com
• Browser → DNS se poochta hai IP kya hai?
• DNS → IP return karta hai.
• Browser → IP par request bhej deta hai.

In-depth DNS Working

• Recursive Server → Query receive karta hai.
• Root Server → TLD (.com, .in, .org) ka location deta hai.
• TLD Server → Authoritative server ka address batata hai.
• Authoritative Server → Final IP deta hai.

MAC Address

MAC = Media Access Control Address

Ye ek unique hardware ID hota hai jo har network device ke sath permanently hota hai.

Example: Aadhaar Card number jo life-time same rehta hai.

Port Numbers

Port = Software gate jahan se ek specific application data bhejta/receive karta hai.

Example: Ghar ke alag-alag kamre – har kamra ek specific purpose ke liye.

Common Ports

• HTTP → 80
• HTTPS → 443
• FTP → 21
• SMTP (Mail) → 25

HTTP vs HTTPS

HTTP (80) → Unsecure, plain text.

HTTPS (443) → Secure, encrypted (SSL/TLS).

IP Technical Details

• IPv4 = 32-bit (range: 0.0.0.0 to 255.255.255.255)
• IPv6 = 128-bit, zyada devices handle karne ke liye.
• IP binary form me represent hota hai (1s aur 0s).

Networking Infrastructure

• LAN = Local network (ghar/office)
• Switch = Local devices connect karta hai
• Router = Internet se connect karta hai
• Public IP = Internet se visible
• Private IP = Sirf LAN me use hota hai
• VPN = Virtual tunnel jo secure connection aur IP hide karta hai

Security Concepts

• HTTP vs HTTPS → HTTPS encrypted aur secure hai.
• Encryption/Decryption → Data ko scramble karna taaki unauthorized user na padh sake.
• Secure Site → Browser padlock dikhata hai.
• Non-Secure Site → "Not Secure" warning aati hai.