Modern-day network communication relies on the TCP/IP (Transmission Control Protocol/Internet Protocol) methodology - a set of protocols defining how devices connect to the Internet. TCP/IP was one of many communication models that had to be established. In the early 80s, the OSI (Open Systems Interconnection) model was developed - it was the first communications model developed. It was adopted by a wide range of companies in the following years.Understanding the OSI ModelThe OSI Model can be understood in many different ways. While many think of it as a conceptual framework for understanding network communications, it can also be considered a model that enables communication among diverse systems. In 1983, major companies widely adopted the model for communication protocol, but in 1984, ISO recognized it as an international standard for communication.What is the purpose of the OSI Model? In a way, the OSI framework can be understood as a common language for computer networking across the world. The framework explains how data is transmitted between two devices. The OSI Model has a seven-layer setup with a specific networking function. The model also visualizes how networks operate, giving protocols for how devices communicate.The Seven Layers of the OSI ModelWhen data or information is passed from one system to another through the OSI model, it passes through seven layers of the sender’s system and climbs back up seven layers of the receiver’s device. These seven abstract layers work together efficiently—each layer has its specialty and works with the layers above and below it to pass down data quickly. The seven layers of an OSI model are explained below.Pic Credit: https://cf-assets.www.cloudflare.com/slt3lc6tev37/6ZH2Etm3LlFHTgmkjLmkxp/59ff240fb3ebdc7794ffaa6e1d69b7c2/osi_model_7_layers.pngPhysical LayerAs the name suggests, the physical layer consists of the physical components of networking. This is the lowest layer in the model, and it transmits raw data across the network. When it travels through this layer, the data is converted from a signal to bits. The hub, modem, cables, etc., are part of the physical layer. The main functions of the physical layer are bit synchronization and bit rate control. Data Link Layer (DLL)The data link layer has multiple functions. First, it ensures node-to-node data transfer, as data transferred from the physical layer is packed into frames. Second, the DLL corrects any errors that might have occurred on the physical layer, thus guaranteeing error and flow control. The DLL has two layers by itself, which help frame the data and add a physical address to it as it passes down to the next layer.Network LayerThe third layer is the network layer, which receives frames from DLL and delivers them to the physical address assigned to them inside the frame. The network layer uses logical addresses to find the frame's destination. Since multiple routes will be available to transmit the frames, this layer also manages packet routing, i.e., selecting the most efficient path to transport the data.Transport LayerThe transport layer mainly works with two layers - the application layer and the network layer. It takes services from the latter and provides services to the former. This layer is mainly responsible for checking the size, errors, and sequencing of the data packets. The layer is also involved in the segmentation and reassembly of data packets, along with the re-transmission of data if there are errors in the pocket.Session LayerThe session layer plays multiple crucial roles - it ensures the communication between two systems by opening and closing communication between them. This layer establishes, maintains, and terminates sessions, facilitating communication among the systems. Another important responsibility of this layer is ensuring the authentication and security of the transmitted data. Presentation LayerAlso known as the translation layer, this layer takes the data from the application layer and alters it to the format required. It also assists the application layer with the encryption and decryption of the data. The presentation layer also handles the syntax of the data being transferred, so it is also referred to as the syntax layer.Application LayerThis is the layer where both the systems interact with the software application that produces data that needs to be transmitted. The application layer synchronizes communication across the systems, acting as a platform for the applications to access the network. Apart from these services, the application layer is also responsible for handling the mail and directory services.Why is the OSI Model Important?One of the main reasons why the OSI Model is still relevant is that it is highly useful in troubleshooting networks and communication issues among systems. Since the model has several layers performing special roles, it is easy to locate the problem in the system through this framework and work on it effectively. The OSI framework is also very helpful for operators in determining the hardware and software needed for their network setups. By understanding this framework, operators can look closely into how different components and layers work in the model.The Bottom Line The OSI model is a conceptual framework and is one of the oldest network frameworks that is still in use today. Established in the early 1980s, the framework has been used as a reference to understand how communication between systems works. The OSI model consists of seven layers: physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and application layer. Each layer has its responsibilities and communicates with the layer next to it to transmit data from one system to another. The OSI Model is relevant even today, even though the Internet does not depend on this model. This is because the framework helps with the easy and quick troubleshooting of network systems.Read Morehttps://devopsden.io/article/explore-the-power-of-serverless-computing-with-aws-lambdaFollow us onhttps://www.linkedin.com/company/devopsden/
