Final answer:
TCP should be used instead of UDP when an application requires reliable data transfer, due to its error checking, guaranteed delivery, and packet order features critical for applications like web browsing, email, and file transfers.
Step-by-step explanation:
TCP (Transmission Control Protocol) should be used instead of UDP (User Datagram Protocol) transport when an application requires reliable data transfer. This is because TCP provides features such as error checking, guaranteed delivery, and order of packets, which are critical for applications where data must arrive intact and in the right sequence. Examples include web browsing, email, and file transfers. On the other hand, UDP is better suited for applications that can tolerate some degree of loss, such as streaming video or VoIP, where the occasional loss of packets does not severely affect the user experience.
TCP establishes a connection between sender and receiver before transmitting data and ensures that all data sent is received correctly at the other end. If any packet is lost during transmission, TCP retransmits that packet until it is successfully received. It also controls data flow to prevent network congestion. Conversely, UDP sends packets without establishing a connection, which could lead to faster dissemination but with the risk of packets getting lost or arriving out of order.
Therefore, you would prefer TCP over UDP for any application where the integrity and reliability of the data transfer are more critical than the raw speed of transmission.