The Open Systems Interconnection (OSI) model is a reference model developed by ISO (International Organization for Standardization) in 1984 as a conceptual framework of standards for communication in the network across different equipment and applications by different vendors. It is now considered the primary architectural model for inter-computing and internetworking communications. Most of the network communication protocols used today have a structure based on the OSI model. The OSI model defines the communications process into 7 layers, dividing the tasks involved in moving information between networked computers into seven smaller, more manageable task groups. A task or group of tasks is then assigned to each of the seven OSI layers. Each layer is reasonably self-contained, so that the tasks assigned to each layer can be implemented independently. This enables the solutions offered by one layer to be updated without adversely affecting the other layers.

ISO defined a group of protocols for internetworking communications based on the OSI model, which are mostly deployed in European countries. ISO protocols are in the layers 3 to 7 and support almost any layer one and two protocols by various standard organizations and major vendors.

ISO Protocols in OSI 7 Layers Reference Model