What is OSI stack?

The OSI (Open Systems Interconnection) model is a conceptual framework that characterizes and standardizes the communication functions of a computing system without regard to its underlying internal structure and technology. It divides the communication system into seven abstraction layers: Application, Presentation, Session, Transport, Network, Data Link, and Physical. Each layer builds upon the functionality provided by the layer below it. It's primarily used as a reference model for understanding and designing network protocols and for describing how data flows between different network devices. While not directly implemented in modern network architectures, it serves as a valuable tool for teaching and troubleshooting network communication.