Which protocol is connection-oriented and can carry messages or emails over the Internet?

• A. HTTP
• B. UDP
• C. TCP
• D. SMTP

Answer: (C)

Understanding connection-oriented transport is the key. A connection-oriented protocol sets up a session before any data moves and guarantees reliable, in-order delivery of that data. TCP does exactly that: it uses a three-way handshake to open a connection, numbers data, sends acknowledgments, and retransmits lost packets, ensuring the entire message arrives intact and in the correct order. Because of this reliability, TCP is the transport layer that can carry higher‑level data like HTTP messages or emails (SMTP) across the Internet.

In contrast, UDP is connectionless and doesn’t guarantee delivery, so it isn’t suited for reliable transfer. HTTP and SMTP are application-layer protocols; they depend on TCP for transport rather than providing the transport service themselves.