1. The OSI Model Keith R. Barry Strayer University CIS 532

2. The Seven Layers Application Presentation Session Transport Network Data Link Physical

3. Application Layer Topmost Layer User-interface: How the user communicates with the network Responsible for interprocess communication

4. Presentation Layer Performs data compression and encryption Essentially interprets data for use in the Application Layer

5. Sessions Layer Controls the connections/dialogues between computers on a network. Utilizes checkpointing, adjournment and termination procedures in both half & full- duplex to control these connections.

6. Transport Layer Provides clear, transparent transfer of data so that upper level layers do not have to concern themselves with data reliability. Data Packet switching is entirely handled on this layer. Network devices such as Routers operate on this layer.

7. Network Layer Ethernets operate on this layer. The Network Layer and Transport Layer can sometimes be confused; however, the Networking Layer deals with complex networking matter whereas the Transport Layer reside on the network itself. Routing and Routers reside on this layer.

8. Data Link Layer This Layer provides procedural and functional means to transfer data from one network entity to another. HDLC and ADCCP are protocols on this layer. Networking devices such as bridges and switches operate on this layer.

9. Physical Layer Defines all electrical and physical specifications for a device on a network. Devices like hubs, repeaters and network adapters operate on this layer. A major function of this layer is the establishment and the termination of a connection with a network.