Class XII Computer Networks Notes

CS (083)

Introduction to Computer Networks: A network allows computers to communicate and share resources.
Evolution of Networking:
- ARPANET: The first operational packet-switching network, the foundation of the internet.
- NSFNET: A backbone network connecting universities, instrumental in expanding internet usage.
- INTERNET: A global network connecting millions of private, public, academic, and government networks.

Concept of Communication: Transfer of data between systems.
Components of Data Communication:
- Sender: The device that sends data.
- Receiver: The device that receives data.
- Message: The data being transferred.
- Communication Media: The physical path or channel through which data is transferred.
- Protocols: Rules governing data communication, ensuring proper data exchange.
Measuring Capacity of Communication Media:
- Bandwidth: The maximum data transfer rate of a communication path.
- Data Transfer Rate: The amount of data transmitted over a channel in a given time (bps).
IP Address: A unique identifier for devices on a network.
Switching Techniques:
- Circuit Switching: A dedicated communication path is established.
- Packet Switching: Data is divided into packets and transmitted independently.

Wired Communication Media:
- Twisted Pair Cable: Common in local networks, offers low-cost data transmission.
- Co-axial Cable: Shielded cable for longer distances and higher data transmission.
- Fiber-optic Cable: Transmits data as light, offering high bandwidth and speed.
Wireless Communication Media:
- Radio Waves: Used in Wi-Fi and cellular networks for long-distance communication.
- Microwaves: High-frequency waves used for long-distance point-to-point communication.
- Infrared Waves: Short-range communication used in remote controls and wireless keyboards.

Modem: Converts digital data to analog signals and vice versa for internet access.
Ethernet Card: Network interface card enabling wired network connections.
RJ45: A connector used for Ethernet networking.
Repeater: Amplifies signals to extend the range of a network.
Hub: A basic networking device that connects multiple devices but does not filter traffic.
Switch: A device that connects devices and filters traffic based on MAC addresses.
Router: Directs data between different networks using IP addresses.
Gateway: Connects two different networks and translates protocols.
Wi-Fi Card: A device enabling wireless network connections.

Types of Networks:
- PAN (Personal Area Network): Smallest network, typically within a single room.
- LAN (Local Area Network): Covers a small geographic area like a home or office.
- MAN (Metropolitan Area Network): Spans a city or large campus.
- WAN (Wide Area Network): Covers large geographic areas, connecting multiple LANs.
Networking Topologies:
- Bus Topology: All devices share a common communication line.
- Star Topology: Devices connect to a central hub or switch.
- Tree Topology: Hierarchical structure with multiple star networks connected.

HTTP (Hypertext Transfer Protocol): For transferring web pages.
FTP (File Transfer Protocol): For transferring files between computers.
PPP (Point-to-Point Protocol): For direct communication between two nodes.
SMTP (Simple Mail Transfer Protocol): For sending emails.
TCP/IP (Transmission Control Protocol/Internet Protocol): Ensures reliable data transmission across networks.
POP3 (Post Office Protocol): Retrieves emails from the server.
HTTPS (HTTP Secure): HTTP with encryption for secure data transfer.
TELNET: Provides remote access to computers.
VoIP (Voice over Internet Protocol): Transmits voice data over the internet.

WWW (World Wide Web): A system of interlinked hypertext documents accessible via the internet.
HTML (Hypertext Markup Language): The standard language for creating web pages.
XML (Extensible Markup Language): A markup language used for data representation and transfer.
Domain Names: A human-readable address for a website (e.g., www.example.com).
URL (Uniform Resource Locator): The address used to access web resources.
Website: A collection of web pages accessible via a domain name.
Web Browser: A software application for accessing websites (e.g., Chrome, Firefox).
Web Servers: Hosts websites and serves web pages to users.
Web Hosting: A service that provides storage space and access for websites.