Iso Osi Reference Model

ISO OSI (Open Systems Interconnect) Reference Model A model based on a proposal developed by the International Standards Organization (ISO) as a first step toward international standardization of the protocols used in the various layers. The Application Layer This is the layer where you do your work, such as sending e-mail or requesting to transfer a file across the network. Without the application layer, you couldn’t create any message or data to send. The Presentation Layer The presentation layer works with the operating system and file system. Here’s where files get converted from one format to another, if the server and client use different formats. Without the presentation layer, file transfer would be restricted to computers with the same format. The Session Layer This layer establishes, manages and terminates connections between applications. The session layer sets up, coordinates, and terminates conversations and dialogues between the applications at each end. It deals with session and connection coordination. The Transport Layer The transport layer makes sure that your packets have no errors and that all the packets arrive and are reassembled in the correct order. Without this layer, you couldn’t trust your network. The Network Layer This layer provides switching and routing technologies, creating logical paths, known as virtual circuits for transmitting data from node to node. Routing and forwarding are functions of this layer, as well as addressing, internetworking, error handling, congestion control and packet sequencing. Without this layer, your data would never get to the right place. The Data Link Layer At this layer, data packets are encoded and decoded into bits. It furnishes transmission protocol knowledge and management and handles errors in the physical layer, flow control and frame synchronization. After the information is on the wire, the data link layer handles any interference. The Physical Layer The physical layer is pure hardware, including the cable, satellite, or other connection medium and the network interface card. This is where electrical signals move around.