Which of the following transport layer protocols is used to support electronic…
2012
Which of the following transport layer protocols is used to support electronic mail?
- A.
SMTP
- B.
IP
- C.
TCP
- D.
UDP
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Correct answer: C
Answer: TCP. Email protocols require reliable, ordered delivery, which TCP provides.
Why TCP: It is connection-oriented and provides reliability (error detection, retransmission, and ordered delivery), features needed for transferring email data.
How email uses it: Application-layer email protocols such as SMTP, POP3 and IMAP run over TCP (for example, SMTP commonly uses TCP port 25).
Why other protocols are not correct: IP is a network-layer protocol (not transport-layer), SMTP is an application-layer protocol (not a transport protocol), and UDP is a transport protocol but is connectionless and unreliable, so it is unsuitable for standard email delivery.
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