Difficulty: Easy
Correct Answer: 1, 3 and 6
Explanation:
Introduction / Context:Different application protocols choose TCP or UDP based on their needs for reliability, ordering, and speed. Identifying which well-known services use UDP is a common exam and troubleshooting task in networking.
Given Data / Assumptions:
Concept / Approach:Recall common port/transport pairs: DHCP uses UDP (ports 67/68), SNMP uses UDP (161/162), and TFTP uses UDP (69). SMTP, FTP, and HTTP rely on TCP for reliability and ordered delivery.
Step-by-Step Solution:
DHCP → UDP (broadcast discovery and lightweight exchanges).SMTP → TCP (reliable email transfer on 25/587/465).SNMP → UDP (simple, low overhead management).FTP → TCP (control on 21, data on 20 or passive ports).HTTP → TCP (classic HTTP/1.1) though modern variants may use QUIC/UDP for HTTP/3, but the classic assumption is TCP.TFTP → UDP (simple, lock-step file transfer on 69).Verification / Alternative check:Remember mnemonic: “D, S, T” (DHCP, SNMP, TFTP) → UDP. Others (SMTP, FTP, HTTP) → TCP.
Why Other Options Are Wrong:2 and 4: Both SMTP and FTP are TCP-based. 1, 2 and 4: Incorrect because SMTP and FTP are not UDP. All of the above: Obviously wrong; not all listed use UDP.
Common Pitfalls:Confusing TFTP with FTP; the “T” stands for Trivial and uses UDP. Also, be cautious with modern HTTP/3 using QUIC over UDP; traditional exam contexts still map HTTP to TCP.
Final Answer:1, 3 and 6
Discussion & Comments