Question
Which of the following transport layer protocols is used to support electronic mail?
Official answer and solution
- Official answer
- C
- From
- Official GATE 2012 answer key
Solution
Identify the transport layer protocol underlying electronic mail services.
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Electronic mail transfer is handled by application-layer protocols such as SMTP (Simple Mail Transfer Protocol) for outbound delivery and relaying, and POP3 / IMAP for mailbox retrieval.
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Electronic mail requires reliable, connection-oriented, and ordered byte stream delivery with zero loss of messages.
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TCP (Transmission Control Protocol) is the transport layer protocol that provides guaranteed reliable end-to-end delivery through sequence numbers, acknowledgements, and retransmissions. SMTP runs on top of TCP using well-known port 25 (or port 587).
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UDP is unreliable and connectionless, IP is a network layer protocol, and SMTP is an application layer protocol. Therefore, the transport layer protocol supporting email is TCP.
C
The answer is the one in the official GATE answer key. The solution is this site's own explanation.
Source
- Paper
- GATE 2012 Computer Science and Information Technology (CS)
- Question
- 22 of 65, printed as CS Q.22
- Section
- Computer Science and Information Technology
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