Computer Network

By Ankit Sir • DevTeam

Unit 1

Computer Network

Definition:
A computer network is a collection of interconnected devices such as computers, servers, routers, and switches that communicate with each other to share data, resources, and services.

Devices are connected using wired (LAN cable) or wireless (Wi-Fi) media
Allows easy data and resource sharing
Improves communication and efficiency

Resources Shared:

Files & Data
Printers
Internet Connection

Example:
Two computers connected using LAN cable or Wi-Fi to share files or a printer.

Unit 2

Internet

Definition:
The Internet is a global network that connects millions of computers and electronic devices worldwide. It allows users to communicate, share information, and access data using the TCP/IP protocol.

Unit 3

Key Features of Internet

Global Network: Enables worldwide communication (India to USA email)
Information Sharing: Google, Wikipedia
Communication: Email (Gmail), Chat (WhatsApp), Video Call (Zoom)
Online Services: Banking, Shopping, Ticket Booking
Education & Entertainment: YouTube, Netflix
Protocols: TCP/IP ensures correct data transfer
WWW: Websites built using HTML, CSS, JavaScript

Unit 4

Types of Computer Networks

PAN: Personal devices, Bluetooth (Mobile ↔ Laptop)
LAN: Building or campus network (Computer Lab)
MAN: City network (Cable TV)
WAN: Large area network (Internet)
VPN: Secure private network over Internet

Unit 5

Network Devices

Hub: Broadcasts data to all devices
Switch: Sends data only to destination device
Router: Connects LAN to Internet
Bridge: Connects two LAN segments
Gateway: Protocol conversion
Modem: Digital to analog conversion
Repeater: Strengthens weak signals

Unit 6

Transmission Media

Guided Media (Wired):

Twisted Pair Cable – Telephone line
Coaxial Cable – Cable TV
Optical Fiber – High speed Internet

Unguided Media (Wireless):

Radio Waves – Bluetooth
Microwaves – Mobile towers
Infrared – TV remote

Unit 7

Network Topologies

Bus: Single cable, easy but risky
Star: Central hub, most common
Ring: Circular path, token passing
Mesh: Highly reliable, costly
Hybrid: Combination of topologies

Unit 8

Network Models

OSI Model: 7 Layers – Application to Physical

TCP/IP Model: 4 Layers – Application, Transport, Internet, Network Access

Unit 9

Protocols & Security

HTTP, HTTPS, FTP, SMTP, DNS, DHCP
Firewall, Encryption, VPN
Virus, Trojan, Worm, Phishing, DoS Attack

Unit 10

Working of Network (Example)

Laptop connects to Wi-Fi Router (LAN)
Router → Modem → Internet (WAN)
Browser sends request using HTTP & TCP/IP
Request reaches Web Server via ISP