OSI-model
In simple terms, the OSI-model is a way to describe how network communication works in seven distinct layers.
1. Physical
Raw bit stream over physical medium.
2. Data Link
The format of the data on the network.
3. Network
What physical path will the data take?
4. Transport
What transmission protocol to use for the data. Examples: TCP and UDP
5. Session
Maintains connections, responsible for controlling ports and sessions.
6. Presentation
Ensures data is in a usable format, and deals with encryption.
7. Application
Human-computer interaction layer, where applications can access the network services.