ONE:Now that you have read the chapter about the OSI model, how would you change it? Are there inefficiencies or redundancies in the model?
In this lab, you’ll examine the layers of the OSI seven-layer model and the TCP/IP model. When you’ve completed this lab you will be able to
● Explain why layered models are used to describe data communication.
● Identify each of the seven layers of the OSI model.
The ISO refers to open systems interconnection model commonly used to standardize and categorize the inner functions of the communication system by dividing it into different layers. This model consists of seven abstract layers with each playing a different function. The layer may serve the layer above it or the layer below it. There is error-free communication within layers throughout the network, layers also provide a path needed by application to send or receive packets across the network. For example two instances in one layer are handled by a horizontal connection.
The seven logical layers play a very great role in data communication. Each layer has a distinctive function to serve the later above it or the layer below it. The following are the seven logical layers of an ISO:
Layer 1: Physical layer
Physical layer is composed of the physical requirements and electrical specifications of data connections. It establishes the devices and the medium of communication. It is usually concerned with establishing and termination connection between two connected nodes across the network thus making it essential to monitor flow control. The physical channel consists of cabling (such as copper or optical cables.), physical Ethernet layers such as Token Ring and FDDI, wireless networks such as radio link and Bluetooth.
Layer 2: Data link layer
Data link layer provides a reliable connection between itself and physical layer. It detects and corrects errors that result from the physical layer. It is further subdivided into sub-layers:
Media Access control (MAC)layer- this layer is charged with the function of controlling how computers gain access to data and regulates the transmission of this information.
Logical link Control (LLC) layer-this layer is concerned with error detection and synchronization of packets.
Data link layer follows the point –to point protocol in the TCP/IP stack.
layer 3: network layer
The network layer provides a functional and steps by step mode of transfers variable data sequences called datagram from one node to the next across the same network. A network system consists of may be interconnected nodes. The nodes have different addresses that allow nodes to connect to it and transfer messages to the required destination node. The network layer has the capability of delivering message by splitting it into several fragments, where each fragment follows a separate route and reassembling the fragment upon reaching the destination while detecting and correcting errors.
Layer 4: transport layer
The transport layer provides a functional and steps by step method of transporting the datagram from the source to the terminus across one or more networks. Transport layer is responsible for control the reliability of links through segmentation/de segmentation and also error control.