The OSI model

Physical Layer: This is the lowest layer, dealing with the physical transmission of data bits over a communication channel. It defines electrical, mechanical, and procedural aspects of connections. Data Link Layer: This layer manages the reliable transmission of data frames between two directly connected nodes. It handles error detection and correction, as well as controlling the flow of data. Network Layer: The network layer is responsible for routing packets across different networks. It determines the optimal path for data transmission from the source to the destination based on network conditions, addressing, and routing protocols. Transport Layer: This layer ensures reliable data transfer between devices. It segments and reassembles data into packets, provides error checking and recovery, and manages end-to-end communication sessions. Session Layer: The session layer establishes, manages, and terminates sessions between applications. It synchronizes data exchange, handles dialogue control, and supports full-duplex or half-duplex communication. Presentation Layer: This layer ensures that data is in a readable format for the application layer. It handles data encryption, compression, and formatting conversions. Application Layer: The topmost layer interacts directly with applications and end-users. It provides network services directly to user applications, such as email, web browsing, and file transfers.