Which layer of the OSI model is responsible for data transmission reliability?

The Transport Layer is crucial for ensuring data transmission reliability within the OSI model. This layer is responsible for providing end-to-end communication services for applications. It primarily deals with the segmentation of data, ensuring that data packets are sent and received in the correct order, and it implements error detection and correction mechanisms.

Protocols like TCP (Transmission Control Protocol), which operates at the Transport Layer, are designed to establish a reliable connection between sender and receiver. TCP ensures that all data is transmitted accurately and in sequence, retransmitting any lost packets as needed. This reliability is particularly important for applications that require data integrity, such as file transfers and web browsing.

While other layers like the Data Link Layer provide error detection and correction for frames at the link level and the Network Layer manages data routing between devices, the Transport Layer's functionalities specifically encompass mechanisms to ensure data is not only delivered but also delivered correctly, making it the layer focused on reliability in data transmission.