Networking Part 2: OSI Model, Protocols, VPN, IPv4/IPv6, Firewall

OSI Model – 7 Layers

Socho tum ek letter likhte ho aur post office ke through bhejte ho. Us letter ko destination tak pahuchne ke liye kai stages se guzarna padta hai — likhna, envelope me daalna, stamp lagana, post office jana, delivery, aur finally receiver tak pahuchna. Yahi kaam computer networks me OSI Model karta hai.​

OSI (Open Systems Interconnection) Model ek conceptual framework hai jo network communication ko 7 layers me divide karta hai:​

1. Physical Layer: Ye layer actual hardware transmission se deal karti hai — cables, switches, voltages.
2. Data Link Layer: Ye layer data packets ko frames me convert karti hai aur MAC addresses ka use karti hai.
3. Network Layer: Ye layer data ko source se destination tak route karti hai using IP addresses.
4. Transport Layer: Ye layer data transmission ke reliability aur flow control ko manage karti hai.
5. Session Layer: Ye layer sessions ko establish, manage, aur terminate karti hai between applications.
6. Presentation Layer: Ye layer data ko encrypt, decrypt, compress, aur decompress karti hai.
7. Application Layer: Ye layer end-user applications ke sath interact karti hai — jaise web browsers, email clients.​

Har layer ka apna specific function hota hai aur ye layers ek dusre ke sath interact karke data transmission ko possible banati hai.​

Network Protocols – Communication Ke Rules

Protocols wo rules hote hain jo define karte hain ki data kaise transmit hoga, receive hoga, aur process hoga network me. Kuch common protocols:​

• HTTP (HyperText Transfer Protocol): Web pages ko load karne ke liye use hota hai.
• HTTPS: Secure version of HTTP, jisme data encryption hoti hai.
• FTP (File Transfer Protocol): Files ko transfer karne ke liye use hota hai.
• TCP (Transmission Control Protocol): Reliable data transmission ensure karta hai.
• UDP (User Datagram Protocol): Faster but less reliable data transmission ke liye use hota hai.
• IP (Internet Protocol): Data packets ko route karta hai source se destination tak.​

Ye protocols ensure karte hain ki data sahi tarike se aur sahi jagah pahuche.​

VPN – Virtual Private Network

Socho tum ek public Wi-Fi use kar rahe ho aur chahte ho ki tumhara data secure rahe. Yahan VPN ka use hota hai.​

VPN ek secure tunnel create karta hai tumhare device aur internet ke beech, jisse tumhara data encrypted hota hai aur hackers se safe rehta hai.​

Benefits of VPN:​

• Public Wi-Fi pe security
• Geo-restricted content access
• Online anonymity

Pv4 vs IPv6 – Internet Addresses

Har device ka ek unique address hota hai jise IP Address kehte hain.​

• IPv4: 32-bit address, e.g., 192.168.1.1.
• IPv6: 128-bit address, e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334.​

IPv6 zyada addresses provide karta hai aur future ke liye scalable hai.​

Firewall – Network Ka Security Guard

Firewall ek security system hai jo incoming aur outgoing network traffic ko monitor karta hai aur unauthorized access ko block karta hai.​

Types of Firewalls:​

• Hardware Firewall: Physical device jo network ke entry point pe hota hai.
• Software Firewall: Computer me installed program jo traffic ko monitor karta hai.​

Firewalls ensure karte hain ki malicious traffic network me enter na kare.​

Client-Server Architecture

Socho tum Google pe kuch search karte ho. Tumhara browser ek client hai jo request bhejta hai aur Google ka server response deta hai.​

Client-Server Architecture me client requests send karta hai aur server responses provide karta hai.​

Is architecture ka use web browsing, email services, aur online gaming me hota hai.​

7. TCP/IP Model – Internet Ka Backbone

TCP/IP Model 4 layers ka model hai jo internet communication ke liye use hota hai:

1. Application Layer: User applications ke sath interact karta hai.
2. Transport Layer: Data transmission ke reliability ko ensure karta hai.
3. Internet Layer: Data packets ko route karta hai.
4. Network Access Layer: Physical network hardware se interact karta hai

click here for computer networking part 1