OSI Reference Model:(Open System Interconnection)

Ø  Introduced around 1980

Ø  Developed by International Standard Organization (ISO)

Ø  It is a layered architecture( consists of seven layers) which explains how the communication happens in between two or more network devices within organisation or internet. Therefore it is theoretical model.

Ø  Each layer defines a set of functions in data communication.

Ø  It is protocol independent standard

Ø  The top three layers i.e. Application layer, Presentation Layer and Session Layer are called software layers because most of functions are performed in application or between processes

Ø  The bottom three layer i.e. Network Layer, Data Link Layer and Physical Layers are hardware layers because most of the hardware devices like Router, Switches and Repeater and Transmission media are involved in these layers.

Application Layer | Presentation Layer | Session Layer | Transport Layer | Network Layer 

Data Link Layer | Physical Layer