Introduction
The Open Systems Interconnection (OSI) Model is a comprehensive reference model that describes and explains how data is exchanged between two systems. It consists of seven layers, each of which has a distinct purpose. These are the Physical, Data Link, Network, Transport, Session, Presentation, and Application layers. Each layer has its key functions essential to the communication process. The OSI model is a layered protocol that provides the structure for data communication between two systems. A communication flow diagram showing the logical and physical connections between organizational layers and departments/divisions of an actual hierarchical business using the OSI Reference Model is shown below:
Layer 7: Application
Layer 7 provides the interface between the user and the network. It is responsible for allowing the user to access various network services and applications, such as web browsers, email clients, and FTP. The seventh layer of the OSI model is the application layer, which provides the interface between the application programs and the lower layers of the OSI model. The application layer provides the necessary services for the user applications to communicate (Shabani et al., 2020). The application layer provides an interface between the user application programs and the OSI model’s lower layers, providing the necessary services for the user applications to communicate. The application layer provides the following services:
The application layer is a critical layer of the OSI model because it provides the necessary services for user applications to communicate with each other, and this layer is responsible for ensuring that all data traveling between systems is safe and secure, as well as providing methods for exchanging information between different user applications. The application layer also plays a role in networking by routing data correctly and providing the necessary functions for communicating with the network (Sullivan et al., 2021). Consequently, the application layer ensures effective communication between user applications. If these services are adequately provided, communications between user applications may be improved or eliminated.
Layer 6: Presentation
The Presentation layer, layer 6 of the TCP/IP protocol suite, is the final layer to process data before it reaches the application layer. It is responsible for data presentation, the process of formatting data in a format the application layer will easily interpret. In other words, it serves as an interface between the application and network layers. Data presentation is essential for end-to-end communication (Shabani et al., 2020). With it, data would be sent across the network in a format that is easier to understand and process, which can lead to errors and lost information, ultimately reducing the system’s overall efficiency.
Layer 5: Session
Layer 5, known as the Session Layer, is one of the seven layers within the OSI model. The purpose of this layer is to establish, maintain, and terminate communication sessions between two computers. The Session Layer provides the logic and synchronization required for data exchange between two systems (Turay, 2019). It is responsible for establishing a session between two computers, which includes coordinating data flow, managing errors, and maintaining session continuity.
Layer 4: Transport
The Transport layer, the fourth layer in the Open Systems Interconnection (OSI) model, provides reliable end-to-end communication between two hosts. Layer 4 is responsible for segmenting data into smaller packets, reassembling them at the destination host, acknowledging the received data, and error-checking (Khan, 2020). The Transport layer is responsible for providing transparent data transfer between two hosts. It provides flow control, congestion control, and reliable delivery of data packets. Additionally, the Transport layer ensures that data is delivered in the correct order and that no packets are lost.
Layer 3: Network
Layer 3 of the Internet Protocol Suite is responsible for providing routing services, which are essential for the smooth functioning of the network infrastructure. Layer 3 of the network stack provides the network’s necessary routing services and helps forward the data packets to their destination. It uses routing protocols such as RIP, OSPF, and BGP to determine the best path for the data packets to reach their destination (Turay, 2019). It also provides Quality of Service (quality of service) by prioritizing the traffic and ensuring that the packets reach their destination promptly. Layer 3 also provides authentication and security services for the data packets traversing the network.
Layer 2: Data Link
The Data Link layer, part of the seven-layer Open Systems Interconnection (OSI) model, provides essential services for the physical layer to ensure reliable data transmission between two nodes on a single link. Its primary responsibility is to ensure reliable data transfer between two nodes by providing access control, error detection and correction, and flow control (Shabani et al., 2020). The Data Link layer also provides the necessary protocols for communicating between nodes on a network, including Ethernet, Token Ring, and FDDI. The Data Link layer is essential for local and wide area networks, providing a reliable connection between computers.
Layer 1: Physical
The physical layer of the internet is the lowest layer of the OSI model and is responsible for the physical transmission of data over a network. Layer 1 is responsible for transmitting the data bits and defines how the data is converted into electromagnetic signals for transmission across the network. It contains physical devices, such as cables, connectors, and repeaters, that are used to physically transfer data from one point to another. The physical layer is divided into two sub-layers: the transmission and reception layers (Khan, 2020). The transmission layer is responsible for transmitting data packets across a network. In contrast, the reception layer is responsible for receiving and decoding these packets, and the process is critical for the proper functioning of the internet. With it, data packets would be recovered and messages delivered to their intended recipient.
Conclusion and Recommendations
The OSI model is a critical internet component, providing a framework for understanding how data is transmitted across a network. The model is divided into seven layers, each responsible for a different aspect of the data transmission process. By understanding the various layers of the OSI model, students can better understand how data is transferred across networks and improve their understanding of internetworking concepts. The International Organization for Standardization (ISO) developed the model, which is standard for all computer networks. The model is often used as a reference for network protocols, such as the TCP/IP model.
References
Khan, K. (2020). The Media Layers of the OSI (Open Systems Interconnection) Reference Model: A Tutorial. Global Journal of Computer Science and Technology, 20(E1), pp. 37–50. https://computerresearch.org/index.php/computer/article/view/1920
Shabani, A., Dermaku, K., & Ademi, G. (2020). Analyzing OSI Model Layers, Benefits, and Disadvantages. https://knowledgecenter.ubt-uni.net/conference/2020/all_events/304/
Sullivan, S., Brighente, A., Kumar, S. A., & Conti, M. (2021). 5G security challenges and solutions: a review by OSI layers. IEEE Access, p. 9, 116294–116314. https://ieeexplore.ieee.org/abstract/document/9514842/
Turay, B. (2019). Analysis of Seven Layered Architecture of OSI Model. Journal For Innovative Development in Pharmaceutical and Technical Science (JIDPTS), 2(12). https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3815237
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