Can you explain the structure and levels of the OSI model used in network communications?

The OSI (Open Systems Interconnection) model is a reference network model that describes seven layers of interaction in network communications:

1. Physical Layer — transmission of bits over physical channels (cables, radio waves).
2. Data Link Layer — organization of frame transmission, error detection and correction, media access control.
3. Network Layer — routing of packets between network nodes (e.g., IP).
4. Transport Layer — reliable data transfer, flow and error control (TCP, UDP).
5. Session Layer — management of communication sessions, establishing, maintaining, and terminating connections.
6. Presentation Layer — data transformation, encoding, encryption.
7. Application Layer — interaction with end applications, high-level protocols (HTTP, FTP, SMTP).

This model helps standardize network protocols and understand how data passes from applications to physical channels and back.