Focus: Walking the Packet (OSI Model in Action)

Learning Intention

We are learning how to trace data through the OSI layers to see how communication actually happens across a network.

Success Criteria

• I can explain how a packet moves through all 7 OSI layers, from sender to receiver.

📝 Seminar Study Notes – “Walking the Packet”

Imagine: You type google.com into your browser. What happens?

1. Application Layer – Browser creates the HTTP request.
2. Presentation Layer – Data is encrypted (TLS/SSL).
3. Session Layer – A session is opened between your browser and Google’s server.
4. Transport Layer – Request is packaged into TCP segments (port 80/443).
5. Network Layer – IP packet is created → source IP (your PC), destination IP (Google).
6. Data Link Layer – Frame is created with your MAC address + router’s MAC.
7. Physical Layer – Bits are transmitted as electrical signals/wireless waves.

At the destination, the process reverses → server receives, unwraps, and responds.

Warm-Up Practice Question

• Which OSI layer adds source/destination IP addresses to the packet?
  • a) Data Link
  • b) Network
  • c) Transport
  • d) Application