YouTube video: https://youtu.be/7IS7gigunyI?si=50tmrnAAC3GYhflv

The OSI (Open Systems Interconnection) model is a fundamental concept that standardizes communication in computer systems. It is the foundation upon which the internet, phones, routers, and almost every networked device communicate. Although traditionally explained from a network engineer’s low-level perspective, this guide interprets the OSI model from a software engineering viewpoint, focusing on concepts relevant to application developers.

Overview of the OSI Model

• Purpose: Standardizes how data is transmitted and received across networked devices.
• Scope in Practice: Every computer system, phone, router, and internet-based device operates on this model.
• Layers: The OSI model consists of seven conceptual layers, each designed to perform specific functions in data communication, working together seamlessly to transmit data from one device to another.

The Seven Layers Summary:

1. Application Layer (Layer 7)
2. Presentation Layer (Layer 6)
3. Session Layer (Layer 5)
4. Transport Layer (Layer 4)
5. Network Layer (Layer 3)
6. Data Link Layer (Layer 2)
7. Physical Layer (Layer 1)

Practical Example: Accessing a Web Application Through the OSI Layers

Imagine a web application running on a server with IP address 100.0.3 and port 80. A mobile phone connected via Wi-Fi wants to load the webpage index.html from this server.

Network Setup: