OSI Model

OSI Model:

The OSI model (Open System Interconnection) is representation how the computer system connects through internet and communicate over network. The OSI model developed by the ISO (International Organization for Standardization).

The OSI model consist of 7 layers and each layer has its own role in communication.

1. Physical Layer:

   The Physical layer is the lowest layer of the OSI model, and it holds the physical entity which is helpful to transfer data and receive data through network. The physical layer contains the data in the form of bits (0’s and 1’s).

2. Data Link Layer:

   The Data Link layer responsible for peer-to-peer connections or end-to-end data inter exchange between two nodes or devices. Chunks of the messages are referred as the packets and the packets are divided into frames. Switches and Bridges are common Data Link Layer Devices

3. Networking Layer:

   The network layer works for the transmission of data from one host to the other located in different networks. It also takes care of packet routing i.e. selection of the shortest path to transmit the packet, from the number of routes available. The sender and receiver’s IP Adress placed in the header by the network layer

4. Transport Layer:

   The transport layer provides services to the application layer and takes services from the network layer. The data in the transport layer is referred to as Segments. It is responsible for the end-to-end delivery of the complete message. Protocols used in the Transport Layer are TCP, UDP.

5. Session Layer:

   Session Layer in the OSI Model is responsible for the establishment of connections, management of connections, terminations of sessions between two devices. It also provides authentication and security. Protocols used in the Session Layer are NetBIOS, PPTP.

6. Presentation Layer:

   The presentation layer is also called the Translation layer. The data from the application layer is extracted here and manipulated as per the required format to transmit over the network.

7. Application Layer:

   At the very top of the OSI Reference Model stack of layers, we find the Application layer which is implemented by the network applications. These applications produce the data to be transferred over the network. This layer also serves as a window for the application services to access the network and for displaying the received information to the user.

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