1-Describe the 7-layer OSI network reference model. List all 7 components. The 7-layer OSI network reference model outlines a hierarchy of abstract building blocks that provide basic protocols and services in a logically separate manner for network standardization (Serpanos & Wolf, 2011; Cowley, 2012; Egyedi, 1997). The OSI network reference model was developed by the International Organization for Standardization (ISO) to facilitate communication between networks by keeping certain standards open rather than proprietary (Serpanos & Wolf, 2011). Each layer is stacked with the physical layer as the lowest and the application layer as the highest, and each layer can be thought of as containing stacks of protocols that make network communications work (Serpanos & Wolf, 2011). A protocol is a set of rules written in a common language that allows computers to communicate with each other. Each communication network is a node, and the corresponding layer on each node communicates with each other. The seven layers, from lowest to highest, are physical, data link control, network, transport, session, presentation, and application. Data travels along the layers on the sending node from the application layer down through the layers until it reaches the physical layer. At the physical layer, data is transmitted on the physical medium to the physical layer at the receiving node. At this point, the data travels along the layers until it reaches the application layer in a format that the end user can use (Cowley, 2012). Layer 2, the data link control layer, is actually divided into two sublayers, the media access layer. control (MAC) and logistics link control (LLC). This change occurred in the reference model due to the I...... middle of paper ......ferent platforms (Melendez & Peterson, 1999). The highest layer in the OSI model is the application layer. While all other layers provide a general service to the other layers, the application does not provide any general service to the other layers (Melendez & Peterson, 1999). The application layer handles items not addressed in any of the lower layers and also handles details specific to deployed applications. Some examples of distributed applications are Hypertext Transfer Protocol (HTTP), Domain Name System (DNS), and Session Initiation Protocol (SIP) (Serpanos & Wolf. 2011). The OSI model names the seventh layer as the application layer but does not specifically include any of the above-mentioned examples since the OSI model is abstract. As end users, we use the application layer every time we enter an HTTP URL into our Internet server.