Open System Interconection Model is used for communication between two computers. It has seven layers. I will describe the layers one by one.

1. Physical Layer: It is the lower layer of OSI. In this we select the voltage level used for representing 0 & 1.
2. Data Link Layer: In this layer, data is divided into frames and sent to Physical layer.
3. Network Layer: Here data is divided into packets.logical address is also given in this layer.
4. Transport Layer: This layer provides error free channel.
5. Session Layer: This layer controls the login sessions.
6. Presentation Layer: In this layer data is encryted and compressed.
7. Application Layer: All the various protocols are included in this layer like http,ftp,SMTP etc. This layer directly interacts with the user.