🌐Computer Networks Basic

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🌐 Computer Network:

🔹 Definition:

A Computer Network is a group of interconnected devices (like computers, phones, servers) that communicate with each other to share resources (like files, internet, printers).

🔹 Why Networks Matter:

• Communication (emails, messages)

• Resource Sharing (printers, files, software)

• Data Access (Google Drive, Dropbox)

• Remote Work (Zoom, Microsoft Teams)

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🏗️ Types of Computer Networks

Type	Full Form	Range	Example
PAN	Personal Area Network	A few meters	Bluetooth between phone and earphones
LAN	Local Area Network	Within a building	Office or Home Wi-Fi
MAN	Metropolitan Area Network	City-wide	College campus network
WAN	Wide Area Network	Country/worldwide	The Internet

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⚙️ Network Components

1. Devices:

   • Host: A computer or phone that sends/receives data.

   • Server: A powerful computer that provides services (like websites).

   • Router: Directs traffic between networks.

   • Switch: Connects devices in the same network.

   • Modem: Converts signals from ISP to internet.

2. Media:

   • Wired (Ethernet cables)

   • Wireless (Wi-Fi, Bluetooth)

3. Protocols:

   • Rules for communication (like grammar for languages).

   • Most common: TCP/IP

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🔢 IP Address & MAC Address

• IP Address: Internet address (like your home address). E.g., 192.168.1.1

• MAC Address: Unique ID of a device's network card (like your fingerprint)

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💬 How Data Travels on a Network

Data is broken into packets and sent from one device to another.

1. Sender breaks the message into packets.

2. Packets are sent over the network.

3. Router decides the path.

4. Receiver reassembles the packets into the original message.

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🔄 OSI Model – The 7 Layers of Networking

This is how communication happens between devices step by step.

Layer	Function
7. Application	User interaction (browsers, apps)
6. Presentation	Data translation, encryption
5. Session	Start/end communication
4. Transport	Reliable delivery (TCP)
3. Network	IP address, routing (IP)
2. Data Link	MAC address, error detection
1. Physical	Cables, radio signals

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🌍 Internet, DNS, and Web

• Internet: A massive WAN connecting billions of devices.

• DNS (Domain Name System): Converts google.com to IP address.

• HTTP/HTTPS: Protocols for web browsing.

• Browser: Sends requests to servers and shows responses.

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🔐 Network Security Basics

• Firewall: Blocks unauthorized access.

• Antivirus: Protects from malware.

• VPN (Virtual Private Network): Secure tunnel for data.

• Encryption: Protects data in transit.