200-901 Network Fundamentals Practice Question
A developer is building a real-time video streaming application that must minimize delay, even if some packets are lost. Which transport protocol is most appropriate, and why?
⚠ Common exam trap
200-901 often tests the misconception that 'UDP guarantees delivery' or that 'TCP is always better because it's reliable' — candidates must recognize that reliability is the wrong optimization for real-time media.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
UDP, because it has lower overhead and no retransmission delay.
UDP is the correct choice because it has minimal overhead (8-byte header vs TCP's 20+ bytes), no handshake, and no retransmission logic, so lost packets do not stall the stream. For real-time video, a late packet is worse than a lost one, so UDP's fire-and-forget model minimizes delay. Application-layer protocols like RTP/WebRTC build on UDP to handle ordering and loss recovery selectively.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
TCP, because it provides flow control to avoid congestion.
Why it's wrong here
TCP's flow control and congestion window throttle transmission when acknowledgements slow, introducing the buffering delay the application must avoid. It is tempting because congestion avoidance protects bulk transfers and downloads, but real-time video prefers UDP, which sends datagrams without waiting for acknowledgements or shrinking its rate.
- ✗
UDP, because it guarantees packet delivery.
Why it's wrong here
UDP provides no delivery guarantee, no acknowledgements and no retransmission; packets may be lost, duplicated or reordered. It is tempting because UDP is genuinely the right transport for real-time video, but the stated justification is false. The correct reasoning is that UDP's lack of guarantees avoids retransmission delay, tolerating loss.
- ✗
TCP, because it ensures all packets arrive in order.
Why it's wrong here
TCP's retransmission and in-order delivery stall the stream whenever packets drop, adding delay precisely when the application tolerates loss instead. It is tempting because ordered delivery suits file transfer and web traffic, where completeness matters, but real-time video needs UDP's fire-and-forget datagrams that let late packets be discarded.
- ✓
UDP, because it has lower overhead and no retransmission delay.
Why this is correct
UDP omits handshaking, acknowledgements and retransmission, so lost packets are not resent and latency stays low. That satisfies the streaming constraint of minimising delay at the cost of occasional loss, which TCP's reliability mechanisms would worsen.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
This 200-901 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-901 exam.