What is the primary function of the transport layer in the OSI model?

The primary function of the transport layer in the OSI model is to ensure the error-free delivery of data segments between devices on a network. This layer is responsible for providing reliable data transfer services, which includes the segmentation of data into smaller packets, ensuring that these packets arrive intact, and managing the flow of data to prevent congestion in the network.

To achieve this, the transport layer uses various protocols that implement error detection and correction mechanisms, such as TCP (Transmission Control Protocol). TCP establishes a connection between the sender and receiver, ensuring that all segments are delivered successfully and in the correct order. If any segment is lost or corrupted during transmission, TCP can detect this and request retransmission, thus providing a reliable communication service.

While other options like routing of packets, encryption and decryption of data, and addressing and framing are important networking functions, they are assigned to different layers within the OSI model. Routing occurs at the network layer, encryption and decryption typically occur at the presentation layer or through application-layer protocols, and addressing and framing are responsibilities of the data link layer. Therefore, the focus of the transport layer on reliability and error management distinguishes it as the correct answer.