Networking · Fundamentals
OSI Model Reference
The seven layers, as a working reference. Click any layer to see what runs there, the devices that operate at that level, how it fails, and the commands you'd reach for when it does. Each layer links to the tools in this suite that touch it.
OSI vs. the TCP/IP model
The OSI model is the teaching reference; the network you actually run is the TCP/IP model. The four-layer TCP/IP model collapses several OSI layers — here's how they line up.
A note on the model: the OSI model is a conceptual framework, not a strict description of any real stack. Real protocols cross layer lines — TLS is often called "Layer 6-ish", and a switch with routing features touches Layers 2 and 3 at once. Treat the layering as a map for reasoning and troubleshooting, not a rulebook.