WEEK 13: OSI Model - M199205zn/Datacomm-CS3 GitHub Wiki

The OSI Model, or Open Systems Interconnection Model, is a conceptual framework used to understand and standardize how different networking protocols interact in a network. It was developed by the International Organization for Standardization (ISO) to guide product developers and facilitate communication between different networking systems.

🔸 Purpose of the OSI Model

Helps in designing and troubleshooting networks.
Allows interoperability between different systems and devices.
Acts as a reference model for understanding network interactions.

📶 The 7 Layers of the OSI Model (from top to bottom):

Layer	Name	Description
7	Application	Interfaces directly with end-user applications (e.g., web browsers, email clients).
6	Presentation	Translates data into a format the application layer can accept (e.g., encryption, compression, formatting).
5	Session	Manages sessions or connections between applications (e.g., logins, session restoration).
4	Transport	Ensures reliable data transfer (e.g., TCP for reliability, UDP for speed).
3	Network	Determines the best physical path for data (e.g., routing, IP addressing).
2	Data Link	Provides node-to-node data transfer, error detection/correction (e.g., MAC addresses, switches).
1	Physical	Transmits raw bits over a physical medium (e.g., cables, switches, voltages).

🧠 Mnemonic to Remember the Layers:

"All People Seem To Need Data Processing" (from Layer 7 to 1)
Or reversed: "Please Do Not Throw Sausage Pizza Away"

📌 Why OSI Is Important:

Encourages modular networking.
Makes it easier to identify where problems occur in a network.
Used in education and training as a guide to understand complex networking systems.

For better understanding: https://www.youtube.com/watch?v=Ca1jnqwqzg0