OSI Model-Seven Layers

OSI MODEL

The open System Interconnection model is created by International Organisation System. It provides standard for different computer systems through which computer systems will be able to communicate with each other.

The OSI model has seven layers, each layer performs a specific job. the seven layers of OSI model are as shown in figure.

Application Layer 

This is the top layer of OSI model. It directly interacts with the data from the user. Example Web browser, Skype, Messenger. It includes HTTP (Hyper Text Transfer Protocol ) and SMTP (Simple Mode Transfer Protocol).

Presentation Layer

 Presentation layer is responsible for transmission, encryption and compression of data.

Session Layer 

This layer is responsible for start and stop communication between two devices. The time when communication starts and stop is known as Session.

Transport Layer 

Transport layer is responsible for end to end communication between the two devices. It takes data from session layer and break them into a small segments. It transmit data using transmission protocol TCP & UDP (Transmit Control Protocol & User Datagram Protocol).

Network Layer

Network layer transmits data between two devices on different network. It takes segments from transport layer and breaks them in to smaller packets. It also decides the best physical path for the data to reach its destination known as routing.

Data Link Layer

Data link layer transfers data between two devices on the same network. It takes the packets from network layer and breaks them into small pieces called Frames. It is responsible for flow control and error control in intra network communication.

Physical Layer

Physical layer contains physical equipment such as cables and switches to transfer the data. It converts data into bit stream (0 or 1), and transfer the raw bit stream over the physical medium.