OSI Reference Model

Modern computer networks are designed in a highly structured way. To reduce their design complexity, most networks are organized as a series of layers, each one built upon its predecessor.
Open System Interconnection (OSI) Reference Model was developed by the International Standard Organization (ISO) to provide a framework for understanding how information is sent from one computer to another. The model is so called because it deals with connecting open systems - that is, the system is open for communication with other systems. The OSI model describe seven layers, with each layer intended to provide a well defined service in order to ensure data has been successfully transmitted between devices.

These layers are:

• Application - Provides different services to the applications.
• Presentation - Converts the information
• Session - Handles problems which are not communication issues.
• Transport - Provides end to end communication control.
• Network - Routes the information in the network.
• Data Link - Provides error control between adjacent nodes.
• Physical - Connects the entity to the transmission media.