Which of the protocols below use TCP at the transport layer?

A. TFTP
B. SMTP
C. SNMP
D. FTP
E. HTTP
F. HTTPS


Answer: B, D, E, F

Explanation:

SMTP (Simple Mail Transfer Profile for email), FTP (File Transfer Protocol), and
HTTP/HTTPS (Hyper Text Transfer Protocol for internet) all use TCP because of the
reliable delivery mechanism. SMTP uses TCP port 25, FTP uses TCP ports 20 and 21,
HTTP uses TCP port 80, and HTTPS uses TCP port 443.

Incorrect Answers:

A, C: SNMP and TFTP use UDP as the transport mechanism. Generally speaking,
protocols that use the keywords "trivial" or "simple" uses UDP, since connectionless, best
effort delivery mechanism usually suffice.

Reference: CCNA Self-Study CCNA INTRO exam certification Guide (Cisco Press,
ISBN 1-58720-094-5) Page 163.