Open System Interconnection (OSI) model, an ISO standard for worldwide communication Networks that defines a networking framework for implementing protocols in seven layers. Layering the communications process means breaking down the communication process into Smaller and Easier to handle interdependent categories. The convention and rules used in such communications are collectively known as Layer protocol. Open Systems Interconnection (OSI) model is developed by ISO (International organization for standardization) in 1984. ISO is the organization dedicated to defining global communication and standards.
This model is called Open System Interconnection (OSI) because this model allows any two different systems to communicate regardless of their underlying architecture. Therefore OSI reference model allows open communication between different systems without requiring changes' to the logic of the underlying hardware and software.
The International standard organization (ISO), in an effort to encourage open networks, developed an open systems interconnect reference model. The model logically groups the functions and sets rules, called protocols, necessary to establish and conduct communication between two or more parties. The model consists of seven functions, often referred to as layers. Every layer Added its own header to the packet from previous layer.
OSI reference model is a logical framework for standards for the network communication. OSI reference model is now considered as a primary standard for internetworking and inter computing. Today many network communication protocols are based on the standards of OSI model. In the OSI model the network/data communication is defined into seven layers. The seven layers can be grouped into three groups - Network, Transport and Application.
• Layer 1, 2 and 3 i.e. physical, data link, and network are network support layers.
• Layer 4, Transport layer provides end to end reliable data transmission.
• Layer 5, 6 and 7 i.e. Session, Presentation, and Application layer are user support layers.
