The Open Systems Interconnection Model (OSI Model) is a theoretical framework for describing the functions of a networking system. In order to facilitate interoperability between diverse devices and applications, the OSI model describes computing functions into a universal set of rules and standards. The connections between computing systems are divided into seven abstraction levels in the OSI reference model: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

The International Organisation for Standardisation (ISO) developed the OSI model in 1984, and it is now used as an architectural paradigm for inter-computer communications. It is a reference model that specifies how information from one computer's software application passes through physical media to another computer's software application.

The seven layers of the OSI Model are

• Physical layer( Layer 1): The physical layer is the lowest layer in the OSI reference model. It is in charge of establishing a physical connection between the devices. Bits of information are stored in the physical layer. It is in charge of sending individual bits from one node to another. When this layer receives data, it converts the signal received into 0s and 1S and sends them to the Data Link layer, which reassembles the frame.
• Datalink layer( Layer 2 ): Data packets are encoded and decoded into bits at OSI Model Layer 2, or the data connection layer. It provides knowledge and management of transmission protocols, as well as handling failures in the physical layer, flow control, and frame synchronisation.
  The media access control (MAC) layer and the logical link control (LLC) layer are two sublayers of the data link layer. The MAC sublayer governs how a networked computer receives access to data and permission to transfer it. Frame synchronisation, flow management, and error checking are all handled by the LLC layer.
• Network Layer( Layer 3 ): The network layer is responsible for data transmission between hosts that are connected to various networks. It also handles packet routing, which is the choosing of the shortest path to send a packet from a large number of options. The network layer places the IP addresses of the sender and receiver in the header.
• Transport layer( Layer 4 ): The transport layer, or OSI Model Layer 4, is responsible for end-to-end error detection and recovery, as well as flow control, and offers transparent data transfer between end systems, or hosts. It assures complete data transfer, which is achieved by the TCP or transport layer protocol, which handles data as a stream of bytes.
• Session layer ( Layer 5 ): The session layer is in charge of coordinating conversations between computers. At layer 5, a session or connection between machines is established, managed, and terminated. Authentication and RECONNECTIONS are also part of the session layer services.
• Presentation layer( Layer 6 ): Based on the syntax or semantics that the application accepts, the presentation layer formats or converts data for the application layer. As a result, it's sometimes referred to as the syntactic layer. This layer can also handle the application layer's ENCRYPTION and decryption needs.
• Application layer ( Layer 7 ): Both the end-user and the application layer interact with the software application directly at this tier. End-user programmes, such as a web BROWSER or Office 365, receive network services through this layer. The application layer locates communication partners, determines resource availability, and coordinates communication. This layer supports file transfer, email, and other network software services as application services. Telnet and FTP are examples of applications that only exist at the application level. This layer includes tiered application architectures.