220-1101 Question 72
Single answerTCP vs. UDPA technician is troubleshooting poor call quality in a small office that uses a cloud-based VoIP phone system. Users report brief audio dropouts during busy periods, but file downloads and web browsing continue to work normally. The technician confirms the phones are reachable and wants to explain why the voice application behaves differently from typical web traffic. Which protocol choice best explains this behavior?
- A
VoIP commonly uses UDP because it prioritizes low latency over retransmitting lost packets.
- B
VoIP commonly uses TCP because its acknowledgments guarantee smooth real-time audio delivery.
- C
Web browsing commonly uses UDP because browser traffic must avoid connection setup delays.
- D
File downloads commonly use UDP because missing packets are acceptable for transferred files.
Show answer and explanation
Correct answer: A
Explanation
This question tests practical understanding of TCP vs. UDP in a real support scenario. UDP is commonly used for time-sensitive traffic such as VoIP and streaming because it minimizes overhead and avoids retransmission delays. TCP is used when reliable, ordered delivery matters, such as web browsing, email retrieval, and file transfers. In CompTIA A+ Core 1, candidates should recognize that UDP's lack of connection establishment and retransmission can improve responsiveness for live communications, while TCP's acknowledgments and error recovery make it better for applications where data accuracy is critical. This aligns with standard networking behavior described in common protocol documentation and vendor best practices for real-time media.
- A. Correct.
Correct. Real-time applications such as VoIP commonly use UDP because it is connectionless and does not wait for acknowledgments or retransmissions before sending additional data. That reduces delay, which is critical for live audio. A small amount of packet loss may cause brief audio dropouts, but retransmission delays would often make calls sound worse. This matches the scenario, where voice quality suffers during congestion while other traffic still functions.
- B. Incorrect.
Incorrect. TCP provides reliable delivery through acknowledgments, sequencing, and retransmissions, but those features can increase latency and jitter. That reliability is valuable for applications like web traffic and file transfers, not typically for real-time voice streams where delayed packets are often less useful than simply moving on to the next audio sample. A common misconception is that guaranteed delivery automatically improves all application performance.
- C. Incorrect.
Incorrect. Standard web browsing uses TCP, most commonly with HTTP or HTTPS over TCP ports 80 and 443. Although reducing delay matters for user experience, browsers depend on reliable, ordered delivery of page content. Choosing UDP for ordinary web traffic would not fit the typical A+ networking model being tested here.
- D. Incorrect.
Incorrect. File downloads generally rely on TCP because the data must arrive completely and in the correct order. Missing packets are not usually acceptable for file integrity. Someone might choose this option by confusing faster delivery with better delivery, but for downloads, correctness and completeness are more important than minimal latency.