Cisco Certified Network Associate (CCNA) Practice Exam

Which of the following is NOT a function of the transport layer?

1. Segmentation of data

2. Flow control

3. Error detection

4. Physical addressing

The correct answer is: Physical addressing

The transport layer of the OSI model is primarily responsible for providing reliable or unreliable delivery of data, ensuring flow control, error detection, and segmentation of data. These functionalities help in managing the communications between different processes running on the source and destination systems. In contrast, physical addressing falls under the purview of the data link layer, which deals with the frame formatting, addressing of devices at a hardware level, and the physical transmission of data over the network medium. It is concerned with how data is physically sent over the network, including details like MAC addresses, rather than managing how segments of data are transmitted reliably across the network. Therefore, the function of physical addressing does not belong to the transport layer, making it the correct identification for the option that does not represent a transport layer function.