Which protocol operates at the Transport layer of the OSI model?

The User Datagram Protocol (UDP) operates at the Transport layer of the OSI model, which is responsible for end-to-end communication and data transfer between systems. The Transport layer provides services such as segmentation, flow control, error detection, and reliability, although UDP is considered a connectionless protocol; it does not provide the same level of reliability as other protocols like TCP (Transmission Control Protocol).

UDP is primarily used for applications where speed is critical, and occasional data loss is acceptable, such as video streaming, online gaming, or VoIP (Voice over Internet Protocol) services. Its lightweight nature allows it to send messages (datagrams) with minimal overhead, making it efficient for transmitting data where timing is more important than guaranteed delivery.

In contrast, HTTP, IP, and FTP operate at different layers of the OSI model. HTTP (Hypertext Transfer Protocol) is an application-layer protocol used for transmitting web pages, IP (Internet Protocol) functions at the Network layer for routing packets across networks, and FTP (File Transfer Protocol) operates at the Application layer for transferring files over a network. These distinctions illustrate why UDP is the correct answer in this context.