Briefly write functionalities of different OSI layers?

The OSI Reference Model includes seven layers. Basic functionality of each of them is as follows:

1. Physical Layer: Controls the transmission of the real data onto the network cable. It explains the electrical signals, line states and encoding of the data and the connector types used. An instance is 10BaseT.

2. Data-Link Layer: This layer takes the data frames or messages from the Network Layer and gives for their actual transmission.

3. Network Layer:  This is responsible for addressing messages and data so they are sent to the correct destination, and for translating logical addresses and names (as a machine name FLAME) into physical addresses.

4. Transport Layer:  Make sure that data is delivered error free, in sequence and with no loss, duplications or corruption.

5. Session Layer: Permit two applications to establish, use and disconnect a connection among them known as a session.

6. Presentation Layer: Verifies the format used to exchange data among networked computers.

7. Application Layer: Provides Applications with access to network services.