Computer Networks of Class XII Computer Science (083)

Computer Networks

Class XII Computer Science (083)

80/20 Rule in Computer Networking

Definition

The 80/20 Rule states that approximately 80% of the network traffic should remain inside the Local Area Network (LAN), while only 20% of the traffic should travel outside the LAN through routers to other networks or the Internet.

Explanation

• 80% Local Traffic – File sharing, printers, local servers and communication inside the LAN.
• 20% External Traffic – Internet browsing, cloud services and communication with other networks.

Advantages

• Reduces network congestion.
• Improves performance.
• Reduces delay (Latency).
• Efficient use of bandwidth.
• Improves network reliability.

Example

• Students access the school server → 80%
• Students browse websites on the Internet → 20%

Computer
↓
NIC
↓
Switch
↓
Bridge (If Required)
↓
Router
↓
Modem
↓
ISP
↓
Gateway (If Required)
↓
Internet

Communication Media & Devices Used in Different Scenarios

Scenario	Communication Media	Networking Device	Reason
Home Network	Wi-Fi / UTP Cable	Modem, Router, Switch	Connect home devices to Internet
School Computer Lab	UTP Cable	Switch, Router	Fast and reliable LAN
Office Building	Optical Fiber / UTP	Switch, Router, Gateway	Connect departments
Bank	Optical Fiber	Router, Gateway	Secure communication
Hospital	Optical Fiber	Switch, Router	Medical data sharing
University Campus	Optical Fiber + Wi-Fi	Router, Switch, Access Point	Campus networking
Mobile Network	Microwave / Radio Wave	Cell Tower, Router	Wireless communication
Satellite Communication	Microwave	Satellite, Modem	Long-distance communication
TV Broadcasting	Radio Waves	Broadcast Tower	Transmit TV signals
ATM Network	Optical Fiber	Router, Gateway	Secure banking
Video Conferencing	Optical Fiber / Wi-Fi	Router, Modem	High-speed communication

Communication Media Selection

Requirement	Communication Media
Short Distance	UTP Cable
Long Distance	Optical Fiber
Wireless Communication	Wi-Fi (Radio Waves)
Mobile Communication	Microwave / Radio Waves
Satellite Communication	Microwave
TV Broadcasting	Radio Waves

Networking Device Selection

Requirement	Networking Device
Connect Computers in LAN	Switch
Connect Different Networks	Router
Internet Connection	Modem
Extend Network Signal	Repeater
Connect Two LAN Segments	Bridge
Different Protocol Networks	Gateway
Connect Computer to Network	NIC
Wireless Connectivity	Wireless Router / Access Point
Broadcast Data	Hub

CBSE Scenario Based Questions

1. School Computer Lab

Media: UTP Cable

Device: Switch

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2. Bank Branches

Media: Optical Fiber

Device: Router + Gateway

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3. Home Wi-Fi

Media: Wi-Fi

Device: Modem + Wireless Router

---

4. Television Broadcasting

Media: Radio Waves

Device: Broadcasting Tower

---

5. Remote Village Internet

Media: Microwave

Device: Satellite Dish + Modem

Exam Tip

1. Identify the communication distance.
2. Select the suitable communication media.
3. Choose the correct networking device.
4. Write one reason for your choice.

Computer Science (083) | Computer Networks | CBSE Class XII