Unit 3: Internet

Internet

The Internet is a global network of interconnected computers that communicate using standard protocols (TCP/IP).
It is the world’s largest network, enabling communication, information sharing, and online services.

Key Features

• Worldwide access
• Fast communication
• Supports multiple services (WWW, Email, FTP, etc.)
• Decentralized network
• Uses packet-switched communication

Internet Architecture

Internet architecture is based on layered design and interconnected networks.

A. Layered Architecture (TCP/IP Model)

Layer	Description
1. Application Layer	Provides network services like HTTP, FTP, DNS, SMTP
2. Transport Layer	Reliable data transfer using TCP/UDP
3. Internet Layer	Logical addressing & routing using IP
4. Network Access Layer	Physical transmission using LAN/WAN

B. Physical Architecture Components

1. Clients -User devices like laptops, mobiles, desktops.
2. Servers - Provide services like websites, email, file hosting.
3. Routers - Connect networks and route IP packets.
4. ISPs (Internet Service Providers) - Provide internet access to users.
5. Backbone Networks - High-speed fiber networks connecting large ISPs.

How the Internet Works (Functioning)

The functioning of the Internet is based on three main concepts:

1. Packet Switching

• Data is divided into small packets.
• Each packet travels independently through the network.
• Packets are reassembled at the destination.

2. IP Addressing

• Each device on the Internet has a unique IP address (IPv4 or IPv6).
• Example: 192.168.1.5

3. Client–Server Model

• Client requests a service → Server responds.
• Example: Browser requests a webpage → Web server sends page.

Basic Internet Services

A. WWW (World Wide Web)

WWW is a system of interlinked hypertext documents accessed via a web browser.

Key Components

• Web pages (HTML)
• Web browsers (Chrome, Firefox)
• Web servers (Apache, Nginx)
• Protocol: HTTP / HTTPS

B. FTP (File Transfer Protocol)

FTP is used for uploading and downloading files between computers on a network.

Features

• Transfers large files
• Supports authentication
• Used for website maintenance

Ports

• FTP: Port 21
• Secure FTP (SFTP): Port 22

C. Telnet

Telnet is a remote login protocol that allows users to access a remote computer as if they were using it locally.

Features

• Command-line access
• Port 23
• Not secure → replaced by SSH

D. Gopher

Gopher is an older menu-driven information retrieval system used before the WWW became popular.

Features

• Text-based menus
• Used for research, academic information
• Mostly obsolete today

Search Engines

Search engines help users find information on the Internet by indexing web pages.

Popular Search Engines

• Google
• Bing
• Yahoo
• DuckDuckGo
• Baidu

How Search Engines Work

1. Crawling – visiting web pages to collect data
2. Indexing – storing data in a database
3. Ranking – showing results based on algorithm relevance

E-mail (Electronic Mail)

E-mail is a method of sending digital messages over the Internet.

Protocols

Protocol	Use
SMTP	Sending mail
POP3	Downloading mail to device
IMAP	Syncing mail across devices

Email Components

• To, CC, BCC
• Subject
• Message body
• Attachments

Examples - Gmail, Outlook, Yahoo Mail.

Web Browsers

A web browser is application software used to access websites on the Internet.

Examples

• Google Chrome
• Mozilla Firefox
• Microsoft Edge
• Safari
• Opera

Functions of Web Browsers

• Send HTTP/HTTPS requests
• Render HTML/CSS/JavaScript
• Allow bookmarking
• Manage cookies and security

Summary Table

Topic	Key Points
Internet	Global network using TCP/IP
Architecture	Based on TCP/IP layers, routers, servers
Functioning	Packet switching, IP addressing, client-server model
Services	WWW, FTP, Telnet, Gopher
Search Engines	Google, Bing etc. perform crawling, indexing, ranking
E-mail	Uses SMTP, POP, IMAP
Web Browsers	Chrome, Firefox, interpret HTML pages

Internet of Things (IoT)

The Internet of Things (IoT) refers to a network of physical devices—such as sensors, machines, vehicles, home appliances—that are connected to the internet and can collect, share, and act on data without direct human involvement.

In simple words: IoT means connecting everyday devices to the internet so they can communicate, automate tasks, and make decisions using data.

Sensors in IoT

Sensors are the core components of IoT systems. They detect changes in the environment and convert them into digital signals.

A sensor is an electronic component that measures a physical quantity (like temperature, light, motion) and converts it into a readable signal.

Features of Sensors

• Accuracy – Measures values correctly
• Sensitivity – Detects even small changes
• Range – Minimum to maximum value it can measure
• Response time – Speed at which it reacts
• Durability – Ability to work in harsh conditions
• Low power consumption – Suitable for battery-operated IoT devices
• Miniature size – Easily fits into small devices

Types of Sensors

A. Environmental Sensors

Sensor Type	What It Measures	Examples
Temperature sensor	Heat level	Thermostat, weather station
Humidity sensor	Moisture in air	Greenhouse, HVAC
Pressure sensor	Air/water pressure	Tire pressure system
Gas sensor	Toxic gases	Smoke detectors

B. Motion & Position Sensors

Sensor Type	What It Measures	Examples
PIR sensor	Human motion	Automatic lights
Accelerometer	Movement/tilt	Mobile phones
Gyroscope	Orientation	Drones, gaming

C. Optical Sensors

| Sensor Type | What It Measures | Examples |
|-------------|------------------|
| Light sensor (LDR) | Light intensity | Street lights |
| IR sensor | Infrared signals | Remote controls |

D. Location Sensors

Sensor Type	Measures	Examples
GPS	Global position	Car tracking
RFID	Object identification	Toll systems

E. Other Types

• Proximity sensor – Detects nearby objects
• Vibration sensor – Used in machine monitoring
• Sound sensor – Detects audio

Smart Cities (IoT in Cities)

A Smart City uses IoT technologies to improve public services, efficiency, and citizen quality of life.

Applications of IoT in Smart Cities

1. Smart Traffic Management - Sensors in signals to reduce congestion, GPS monitoring of vehicles
2. Smart Parking - Sensors detect free parking spaces
3. Smart Waste Management - Dustbins with sensors for fill levels
4. Smart Street Lighting - Lights turn ON/OFF based on movement or sunlight
5. Public Safety - CCTV + AI + IoT for real-time crime detection
6. Air Quality Monitoring - Sensors monitor pollution levels
7. Water Supply Management - Leak detection sensors
8. Smart Energy Grids - Smart meters for electricity consumption

Goal: Reduce cost, energy, traffic, crime, and improve services.

Industrial Internet of Things (IIoT)

The Industrial Internet of Things (IIoT) refers to the use of IoT in industries and factories to improve automation, productivity, and efficiency.

Features of IIoT

• High accuracy sensors
• Real-time monitoring
• Predictive maintenance
• Automation with AI and robotics
• Remote machine control

Applications

1. Smart Manufacturing - Machines connected to cloud for monitoring
2. Predictive Maintenance - Sensors detect machine faults before breakdown
3. Supply Chain Optimization - RFID for warehouse tracking
4. Energy Management - Monitoring energy consumption in factories
5. Industrial Robotics - Automated robots in assembly lines
6. Oil & Gas Industry - Sensor-based leak and pressure monitoring

Benefits of IIoT

• Reduced downtime
• Better quality control
• Cost reduction
• Increased safety
• Data-driven decisions

Summary Table

Topic	Explanation
IoT Definition	Network of connected devices that communicate via the internet
Sensors	Devices that detect physical changes and convert them into signals
Sensor Types	Temperature, humidity, light, GPS, PIR, accelerometer, etc.
Smart Cities	IoT for traffic, waste, water, streetlights, pollution control
IIoT	IoT in industries to automate, monitor, and optimize production