What Are OSI Layers?
For networts the Open Systems Interconnection (OSI) model has seven layers that computer systems use to communicate over a network. Modern IT networks are based on the simpler TCP/IP model but OSI layers are still widely referred to, as the layering helps to visualise a network, isolate and resolve networking problems.
| Level | Layer | Description |
|---|---|---|
| 7 | Application | Human-computer interaction layer, where applications can access the network Services |
| 6 | Presentation | Ensures the data is in a usable format and is where data encryption occurs |
| 5 | Session | Maintains connections and is responsible for controlling ports and sessions |
| 4 | Transport | Transmits data using transmission protocols including TCP and UDP |
| 3 | Network | Decides which physical path the data will take |
| 2 | Data Link | Defines the format of the data on the network |
| 1 | Phsyical | Transmits raw bit stream over the physical medium |