# OSI Model
Confidence: high
Last verified: 2026-05-22
Generation: human_only


## TL;DR

The OSI (Open Systems Interconnection) model describes 7 layers of network communication. While not literally implemented, it's the standard mental model for understanding networking. Layers: Physical, Data Link, Network, Transport, Session, Presentation, Application.

## Core Explanation

Layer 1: cables, radio, bits on wire. Layer 2: MAC addresses, switches. Layer 3: IP addresses, routers. Layer 4: TCP/UDP, ports. Layers 5-7: often merged in TCP/IP model. TCP/IP model (4 layers): Link, Internet, Transport, Application — simpler, maps directly to real implementations.

## Further Reading

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