Which layer of the OSI model is responsible for ensuring reliable data transfer?

The layer of the OSI model that is responsible for ensuring reliable data transfer is the Transport layer. This layer's primary function is to provide end-to-end communication services for applications. It establishes a connection between the sender and receiver, ensuring that data packets are delivered accurately and in the correct sequence.

The Transport layer implements error detection and correction mechanisms, acknowledging received packets and retransmitting lost or corrupted packets. It is also responsible for flow control, ensuring that the sender does not overwhelm the receiver with too much data too quickly. By handling these tasks, the Transport layer plays a crucial role in maintaining the integrity and reliability of the communication process.

In contrast, the other layers focus on different aspects of data transmission. The Network layer is primarily concerned with routing packets through the network, while the Session layer manages sessions between applications. The Application layer provides network services directly to user applications, but it does not handle data transfer reliability like the Transport layer does.