Which OSI model layer is primarily responsible for end-to-end communications?

The Transport layer is primarily responsible for end-to-end communications in the OSI model. This layer ensures that data is transferred reliably and in the correct sequence from the sender to the receiver. It provides mechanisms for error detection and correction, flow control, and segmentation of data into smaller packets that can be efficiently transmitted over the network.

By managing the reliability of the connection, the Transport layer allows for the establishment of virtual circuits, which means that it can provide either connection-oriented communication (like TCP) or connectionless communication (like UDP). The Transport layer plays a crucial role in ensuring that data intended for one end device can be accurately delivered and reassembled once it reaches the other end, which is critical for applications that rely on full and accurate data delivery, such as file transfers or video streaming.

Other layers, such as the Physical layer, Data link layer, and Session layer, address different aspects of networking and do not focus specifically on the end-to-end communication reliability that the Transport layer provides.