OSI

A conceptual framework that standardizes how different networking systems communicate. Developed by the International Organization for Standardization (ISO), it divides the network communication process into seven distinct layers, each with specific functions and responsibilities. This layered approach enables developers to design interoperable networking hardware and software, as well as diagnose network issues.

The seven layers, from top to bottom, are:

1. Application: Interfaces directly with end-user software (e.g., web browsers, email clients).
2. Presentation: Translates, encrypts, and compresses data (e.g., file formats, character encoding).
3. Session: Manages connections between devices, handling initiation, maintenance, and termination.
4. Transport: Ensures reliable data transfer with error checking and flow control (e.g., TCP, UDP).
5. Network: Determines data routing and addressing across networks (e.g., IP).
6. Data Link: Handles node-to-node data transfer and error detection (e.g., Ethernet, MAC addressing).
7. Physical: Transmits raw bitstreams over physical media (e.g., cables, radio waves).

While modern networking protocols, such as TCP/IP, don’t follow the OSI model exactly, the OSI framework remains a foundational reference in networking education and troubleshooting. It clarifies where problems occur and helps maintain structured communication across diverse systems.