What is OSI Model ?

      Open System Interconnection Model (OSI) which is the basic and most important concept to understand in Networking. OSI Model consists of seven layers, each layer is designed for specific Networking task. These layers refer how the communication between several systems has to be done. OSI Model is the Standard way of communication on Network.

Encapsulation:    The process of adding the layer covers.

De-multiplexing: The process of removing layer covers.

Physical Layer:

                        This is the first layer of OSI Reference Model. Physical Layer is the communication medium where multiple systems physically connected with each other. It’s responsible for transmission.

Data Link Layer:

                        It is Responsible for MAC, Identification, Error detection, Collision Management. It transfers the frame through Physical Layer. Switch operates at this layer.

Network Layer:

                        Packet Switching takes place here. Network Layer routes the data across the network. Internet Protocol (IP) works at this layer. Routers work at this Layer, which we call Layer 3 devices.

Transport Layer:

                        It is responsible for delivering data to the host computers. Transport Layer Provides reliability, flow control, which helps to avoid congestion during the data transmission. Transmission Control Protocol (TCP), User Datagram Protocol (UDP) works at this layer.

Session Layer:

                        Session Layer remembers the context, like which program you are working at, so that it makes to get the related reply easily. Session layer understand which particular context coming from which particular system.

                         

Presentation Layer:

                        In a simple way it acts like a translator. Which means it presents the data in a way which helps the other system on the network able to understand it easily.  Data compression and decompression, encryption and decryption performed here.

Application Layer:

                        It is the top most layer of the OSI Model. The application layer provides the environment for application data to be carried from one place to another. This means if we are working at web browser that data must be carried by HTTP. HTTP, FTP, Telnet, POP3, SMTP are some protocols works at this layer.

How does the OSI Model functions.