Which statement best describes TCP and UDP?

• A. UDP is connection-oriented and reliable with sequencing.
• B. TCP is connectionless and best-effort delivery.
• C. UDP provides flow control and congestion handling.
• D. TCP is connection-oriented and reliable with sequencing; UDP is connectionless and best-effort.

Answer: (D)

Differentiating TCP and UDP comes down to how they handle connections and reliability. TCP is connection-oriented, meaning a session is established before data moves. It uses sequencing to keep segments in the correct order and guarantees delivery through acknowledgments and retransmission when something is lost. It also includes mechanisms for flow control, to prevent overwhelming the receiver, and congestion control, to adjust sending rate based on network conditions. UDP, in contrast, is connectionless and does not guarantee delivery, ordering, or protection against duplicates; it sends datagrams with no built-in retransmission or sequencing. So the statement that TCP is connection-oriented and reliable with sequencing, while UDP is connectionless and best-effort, accurately describes their fundamental behavior. This explains why TCP is chosen for reliable tasks like web pages and file transfers, while UDP is preferred for low-latency applications where some data loss is acceptable.