200-901 Network Fundamentals Practice Question
Which TWO of the following are benefits of using UDP over TCP for real-time applications?
⚠ Common exam trap
Cisco often tests the misconception that 'reliable' means 'better' for all applications, but candidates must recognize that real-time apps prioritize low latency over reliability, making UDP's lack of guarantees a feature, not a flaw.
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
✓
Lower latency due to no connection setup
Option A is correct because UDP is connectionless: it performs no three-way handshake (SYN/SYN-ACK/ACK) before sending data, so there is no round-trip setup delay, which directly reduces latency for real-time traffic such as VoIP or live video. Option C is correct because the UDP header is only 8 bytes (source port, destination port, length, checksum) versus TCP's minimum 20-byte header, so UDP imposes less per-packet overhead and leaves more bandwidth for payload. Option B is incorrect because guaranteed delivery is a TCP feature provided by sequence numbers and acknowledgments with retransmission; UDP offers best-effort delivery with no retransmission. Option D is incorrect because in-order delivery is also a TCP function achieved via sequence numbers and reassembly, whereas UDP datagrams may arrive out of order. Option E is incorrect because congestion control (slow start, congestion avoidance, etc.) is implemented by TCP, while UDP has no built-in congestion control and relies on the application or protocols like RTP/QUIC to manage it.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Lower latency due to no connection setup
Why this is correct
UDP is connectionless, so it skips the TCP three-way handshake before transmitting. Real-time applications such as voice and video avoid that setup delay, reducing latency and satisfying the stem's requirement for timely delivery over reliability.
- ✗
Guaranteed delivery of all packets
Why it's wrong here
UDP has no acknowledgements or retransmission, so lost datagrams are simply dropped; guaranteed delivery is a TCP function. It is tempting because reliability sounds universally desirable, yet real-time media often prefers dropping stale packets over retransmitting them.
- ✓
Reduced overhead from smaller header size
Why this is correct
UDP's eight-byte header, versus TCP's minimum twenty bytes, cuts per-packet overhead, satisfying the low-latency constraint real-time traffic demands. This smaller header reduces bandwidth consumption and processing delay, letting time-sensitive streams such as voice or video transmit promptly without TCP's connection setup and acknowledgement fields.
- ✗
In-order packet delivery
Why it's wrong here
UDP provides no sequencing or reordering mechanism; datagrams arrive in whatever order the network delivers them, so in-order delivery is a TCP guarantee. It is tempting because applications can reorder packets themselves, but that is application logic, not a UDP benefit.
- ✗
Congestion control to avoid network overload
Why it's wrong here
UDP has no congestion window or slow-start; senders transmit regardless of network state, leaving congestion control to TCP or to the application. It is tempting because avoiding overload sounds beneficial, but that mechanism is precisely what adds TCP latency.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.