The OSI Model Overview
📌 The OSI (Open Systems Interconnection) model, developed by the ISO in the mid-1980s, established networking standards for data flow.
⚙️ Data transmission, like sending a file or clicking a link, initiates a flow across seven distinct layers of abstraction.
🌐 This model ensures that interconnected devices can communicate based on a common networking standard.

Data Flow Across Layers (7 to 1)
1. 🧑‍💻 Application Layer (7): Acts as the user's window, providing access to network services like resource sharing.
2. ✍️ Presentation Layer (6): Functions as the translator, formatting data, potentially translating formats, and handling encryption/control information.
3. 🤝 Session Layer (5): Manages session establishment, maintenance, and termination between two application processes, handling security, name recognition, and logging.
4. 🛡️ Transport Layer (4): Ensures reliable and error-free delivery by scanning data, acknowledging receipt, and breaking data into SEGMENTS (firewalls often operate here).
5. 🗺️ Network Layer (3): Determines the path packets will take (Routing), encapsulates segments into PACKETS, and adds source and destination IP addresses.
6. 🔗 Data Link Layer (2): Converts packets into FRAMES for specific networks, ensuring error-free transfer between nodes, often involving network switches and MAC addresses.
7. 🔌 Physical Layer (1): Transforms frames into bits and sends them over the physical hardware or media (e.g., Ethernet).

Data Reception Flow (1 to 7)
🔄 Data received moves back up the layers, from the physical layer encoding bits back to frames, up through validation at the transport layer.
🖥️ The process culminates at the Application Layer, where the data is finally translated back into a readable format presented to the user.

Key Points & Insights
➡️ The Presentation Layer acts as the network's translator, ensuring data compatibility between application layers on different machines.
➡️ Firewalls can operate at multiple layers, with lower layers (like the Network Layer) sometimes offering more comprehensive network security.
➡️ The Transport Layer is crucial for data integrity, breaking data into SEGMENTS and ensuring retransmission if acknowledgment is not received.
➡️ Every interaction across the internet, such as clicking a link, involves this complex, standardized journey through the seven layers of the OSI model.

📸 Video summarized with SummaryTube.com on Dec 04, 2025, 15:07 UTC