What does the Transport Layer of the TCP/IP Model handle?

The Transport Layer of the TCP/IP Model is responsible for providing end-to-end communication services for applications. Its main function is to manage the process of sending and receiving data between applications, predominantly utilizing protocols such as TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).

TCP is a reliable, connection-oriented protocol that ensures data is delivered in the correct order and without errors, handling error correction and flow control. UDP, on the other hand, is a connectionless protocol that provides a faster, but less reliable service, suitable for applications where speed is critical and some data loss is acceptable. The distinction between these two protocols is crucial as they cater to different types of applications and their specific needs in terms of data transmission.

The other choices refer to different layers or functions within the networking model. For instance, routing packets across networks is a function of the Network Layer, while the physical transmission of data pertains to the Physical Layer. High-level functions like email generally fall under the Application Layer, which is responsible for providing specific services to end-user applications. Thus, the primary focus of the Transport Layer is on the method of transporting data packets through these protocols, which is why the correct answer emphasizes sending packets through TCP or UDP.