The OSI model (Open Systems Interconnection Reference Model) is a model for transmitting data between various computer systems. It consists of 7 independent layers that are responsible for different tasks. The higher layers are based on the lower one. 1. Physical layer, 2. Data Link layer, 3. Network layer, 4. Transport layer, 5. Session layer, 6. Presentation layer, 7. Application layer.

A body of standards set by the International Standards Organization (ISO) to define the activities that must occur when computers communicate. There are seven layers, and each contains a specific set of rules to follow at that point in the communication. Each layer builds upon the last, adding functionality to the services of the previous layer. The OSI Model is concerned with communication (the structure of passing messages) rather than implementation (what passes the message). For example, e-mail is a task of the Application layer. The Application layer uses all of the layers below it to deliver the e-mail -- the Presentation layer formats the look of the e-mail and the Physical layer actually transports the binary data across the network.

A model of communications between cooperating devices. It defines a 7-layer architecture of communication functions. The OSI reference model is a telecommunication networking architecture developed by International Organization for Standardization (ISO) and adopted as an international standard; also known as Reference Model for Open Systems Interconnection.