1. Introduction to Computer Networks
Definition: A computer network is a collection of interconnected computers and devices that can share data, resources, and services.
Purpose of networking:
Resource sharing (files, printers, software).
Communication (email, video calls, messaging).
Data sharing and transfer.
Centralized data management.
2. Types of Networks (Based on Area Coverage)
PAN (Personal Area Network)
Covers a very small area (few meters).
Used for connecting personal devices like smartphones, laptops, earphones, etc.
Example: Bluetooth, Infrared.
LAN (Local Area Network)
Limited to small areas such as office, school, or building.
High speed, low cost.
Example: Network in a school computer lab.
MAN (Metropolitan Area Network)
Covers a city or town.
Used by cable TV providers, ISPs.
Example: Broadband network in a city.
WAN (Wide Area Network)
Covers large geographical areas, even across countries.
Internet is the best example of WAN.
Expensive and slower compared to LAN.
3. Network Topologies
Definition: The arrangement of computers and devices in a network is called network topology.
Bus Topology
All computers are connected to a single communication line (bus).
Cheap but failure of the main cable stops the network.
Star Topology
All devices connect to a central hub/switch.
Easy to install, but hub failure stops the entire network.
Ring Topology
Devices connected in a circular manner.
Data travels in one direction.
Failure of one device affects the whole network.
Mesh Topology
Every device connected to every other device.
Very reliable, but costly and complex.
4. Networking Devices
Modem – Converts digital signals into analog and vice versa for internet connection.
Switch – Connects multiple devices in a LAN and forwards data intelligently.
Hub – Connects multiple devices but broadcasts data to all (less efficient than switch).
Router – Connects different networks (LAN to WAN, LAN to Internet).
Access Point (AP) – Provides wireless connectivity.
Gateway – Acts as an entry/exit point for networks using different protocols.
5. Transmission Media
Two main categories:
Wired Media
Twisted Pair Cable: Cheap, used in LAN.
Coaxial Cable: Faster, used for TV and internet.
Optical Fiber: High speed, long distance, expensive.
Wireless Media
Radio Waves: Wi-Fi, Bluetooth.
Microwaves: Satellite communication, cell phones.
Infrared: Remote controls, short distance communication.
6. Protocols
Definition: Rules for communication between computers in a network.
Important Protocols:
HTTP/HTTPS: Transfer of web pages.
FTP: File transfer.
SMTP/POP3/IMAP: Email transfer.
TCP/IP: Core internet protocol.
VoIP: Voice over Internet (WhatsApp, Skype).
7. IP Address
Definition: A unique numeric label assigned to each device on a network.
Types:
IPv4: 32-bit address, written as 4 numbers (e.g., 192.168.0.1).
IPv6: 128-bit address, written in hexadecimal (e.g., 2001:0db8:85a3::7334).
8. Domain Name System (DNS)
Converts domain names (like www.google.com) into IP addresses.
Easy for humans to remember.
9. Internet Basics
Definition: A global network connecting millions of computers.
Services of Internet:
Email
World Wide Web (WWW)
Social Media
Online Shopping/Banking
Cloud Storage
Video Conferencing
10. Cloud Computing
Definition: Delivering services (storage, software, computing power) via the internet.
Examples: Google Drive, Microsoft OneDrive, AWS.
Advantages: Cost saving, scalability, accessibility.
11. Cyber Security
Threats:
Virus, Worms, Trojan, Phishing, Hacking, Spyware.
Safety Measures:
Strong passwords.
Firewalls and antivirus software.
Regular updates.
Two-factor authentication.
12. E-Governance & E-Commerce
E-Governance: Use of internet by government for services (e.g., Aadhaar, online tax filing).
E-Commerce: Buying and selling products/services online (Amazon, Flipkart).
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