The Open Systems Interconnection (OSI) model is a conceptual framework that defines how data communication should occur between different systems. It was developed by the International Organization for Standardization (ISO) in 1984 to standardize communication between various computer systems. The OSI model consists of seven layers, each of which provides a specific function for data communication. These layers are: Physical Layer: This layer is responsible for the physical transmission of data over a communication channel. It defines the electrical and mechanical characteristics of the interface between the device and the transmission medium. Data Link Layer: This layer is responsible for the transfer of data between adjacent network nodes. It provides error detection and correction, and flow control. Network Layer: This layer is responsible for the delivery of packets across multiple networks. It provides routing and addressing services. Transport Layer: This layer is responsible for end-to-end message transmission. It provides reliable data delivery and ensures that packets are delivered in order. Session Layer: This layer is responsible for establishing, maintaining, and terminating connections between devices. It provides services for synchronization, checkpointing, and recovery. Presentation Layer: This layer is responsible for the conversion of data into a format that can be understood by the application. It provides services such as encryption, compression, and translation. Application Layer: This layer is responsible for providing services to the end-user applications. It provides services such as email, file transfer, and remote login.
The OSI model also defines various protocols that are used at each layer of the model. These protocols include: Physical Layer protocols such as Ethernet, USB, and Bluetooth Data Link Layer protocols such as Wi-Fi, Ethernet, and PPP Network Layer protocols such as IP, ARP, and ICMP Transport Layer protocols such as TCP and UDP Session Layer protocols such as NetBIOS and RPC Presentation Layer protocols such as SSL and TLS Application Layer protocols such as HTTP, FTP, and SMTP The use of the OSI model and its associated protocols allows for standardization of communication between different systems, ensuring that data can be transmitted and received correctly. Understanding the OSI topology is essential for network administrators and IT professionals, as it provides a framework for troubleshooting and configuring network devices.