Layers of OSI model and real-world scenarios

Application Layer (Layer 7)

• Example: Web browsers (like Chrome or Firefox) and applications such as WhatsApp or email clients.

• Real-world scenario: When you type a website address and hit enter, your browser uses the HTTP protocol to request a web page from a server. Similarly, when you send an email, your email app uses SMTP or IMAP to communicate with the email server16.

Presentation Layer (Layer 6)

• Example: Data format translation and encryption.

• Real-world scenario: Your browser converts data formats (like JPEG for images or MP3 for audio) so they display correctly. It also handles encryption and decryption when you access secure sites (HTTPS), ensuring your data is readable only by the intended recipient1.

Session Layer (Layer 5)

• Example: Session management in applications.

• Real-world scenario: When you log into a website and stay logged in as you browse different pages, the session layer manages and maintains that connection. For chat apps like WhatsApp, it keeps you connected so you can send and receive messages in real time16.

Transport Layer (Layer 4)

• Example: TCP and UDP protocols.

• Real-world scenario: When you download a file, TCP ensures all parts arrive intact and in order, resending any missing pieces. For live video calls, UDP is often used because it’s faster and can tolerate some lost data (which might appear as a glitch in the video), prioritizing speed over perfect accuracy156.

Network Layer (Layer 3)

• Example: IP addresses and routing.

• Real-world scenario: When you send a message or access a website, the network layer assigns source and destination IP addresses, ensuring your data finds the right path across the internet to reach the correct device, even if it has to pass through multiple routers156.

Data Link Layer (Layer 2)

• Example: Ethernet and MAC addresses.

• Real-world scenario: On your home Wi-Fi, the data link layer ensures your message is sent to the correct device on your local network by using MAC addresses. It’s like making sure a letter is delivered to the right apartment in a building156.

Physical Layer (Layer 1)

• Example: Cables, Wi-Fi signals, and hardware.

• Real-world scenario: This is the actual hardware-like Ethernet cables, fiber optics, or Wi-Fi radio waves-that carries your data as electrical signals, light pulses, or radio waves from one device to another