Reference Model, also referred to as the OSI seven-layer model. Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical Levels 1 through 3 are network specific, and will differ depending on what physical network you are using. Physical Describes the physical media of the network. Network Manages the connections to other machines on the network. Transport Ensures error-free data transmission.
Session Manages the connections between applications.
Presentation Ensures that data is presented to the applications in a consistent fashion. Application Comprises the applications that use the network. Note that while the OSI Reference Model is useful for discussing networking concepts, many networking protocols do not closely follow the OSI model. Each layer in the OSI model communicates with the corresponding layer on the remote machine as shown in the OSI Reference Model figure . The layers pass data only to the layers immediately above and below.