Question

OSI reference model has _________ layers.

• A. $7$
• B. $8$
• C. $4$
• D. $3$

Answer 1

Answer: (A)

OSI (open systems interconnection) reference model has 7 layers.

OSI (Open Systems Interconnection) is a reference model for how applications communicate over a network.

Layers of OSI model are:-

1) Application layer:-

Application Layer is the top-most layer of the seven layered Open Systems Interconnection (OSI) network model. Real traffic data will be often generated from the Application Layer. This may be a web request generated from HTTP protocol, a command from telnet protocol, a file download request from FTP protocol etc.

2) Presentation layer:-

The position of Presentation Layer in seven layered Open Systems Interconnection (OSI) model is just below the Application Layer. When the presentation layer receives data from the application layer, to be sent over the network, it makes sure that the data is in the proper format.

3) Session layer:-

The position of Session Layer of the Seven Layered Open Systems Interconnection (OSI) model is between Transport Layer and the Presentation Layer. Session layer is the fifth layer of seven layered Open Systems Interconnection (OSI) Model. The session layer is responsible for establishing, managing, and terminating connections between applications at each end of the communication.

4) Transport layer:-

The fourth layer of the seven layers of Open Systems Interconnection (OSI) network mode is the Transport layer. The Transport layer handles transport functions such as reliable or unreliable delivery of the data to the destination. On the sending computer, the transport layer is responsible for breaking the data into smaller packets, so that if any packet is lost during transmission, the missing packets will be sent again.

5) Network layer:-

The third layer of the seven layers of Open Systems Interconnection (OSI) network model is the Network layer. The Network layer of the OSI model is responsible for managing logical addressing information in the packets and the delivery of those packets to the correct destination.

6) Data link layer:-

The second layer of the seven layers of Open Systems Interconnection (OSI) network model is called the Datalink layer. The Data Link layer resides above the Physical layer and below the Network layer. Datalink layer is responsible for providing end-to-end validity of the data being transmitted.

7) Physical layer:-

The first layer of the seven layers of Open Systems Interconnection (OSI) network model is called the Physical layer. Physical circuits are created on the physical layer of Open Systems Interconnection (OSI) model. Physical layers describe the electrical or optical signals used for communication.