What is the OSI model? What are L2, L3, L7?

The OSI (Open Systems Interconnection) model is a reference model for network interaction, dividing communication into 7 layers:

1. Physical (L1): transmission of bits over physical media.
2. Data Link (L2): organization of frame transmission, error detection and correction.
3. Network (L3): routing of packets between nodes (e.g., IP).
4. Transport (L4): reliable data delivery (TCP, UDP).
5. Session (L5): management of communication sessions.
6. Presentation (L6): data transformation, encoding.
7. Application (L7): interaction with applications (HTTP, FTP).

L2 — data link layer, responsible for data transfer between neighboring nodes in the network.

L3 — network layer, handles routing and delivery of packets between different networks.

L7 — application layer, where protocols that enable interaction between applications and users operate (e.g., web protocols).