PK0-005 Practice Question: Basics of IT Infrastructure and IT Project Management
A company is deploying a new VoIP system. Which network infrastructure component is most critical for ensuring voice quality?
⚠ Common exam trap
Candidates often confuse bandwidth capacity (throughput, cable speed) with traffic prioritization, assuming that faster cables or higher firewall throughput alone guarantee voice quality, when in fact QoS is the only mechanism that prevents jitter and packet loss for real-time traffic.
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
✓
Switch QoS settings
Voice quality over VoIP is highly sensitive to latency, jitter, and packet loss. Switch QoS settings (e.g., 802.1p/DSCP marking, strict priority queuing) ensure that voice traffic is prioritized over data traffic, preventing delays and dropped packets that degrade call quality. Without proper QoS, even high-bandwidth links will suffer from poor Mean Opinion Scores (MOS).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Cable category
Why it's wrong here
Cable category sets the supported bandwidth and distance rating, but voice quality depends on latency, jitter and loss, which adequate category alone does not control. It is tempting because cabling underpins the network, and would be correct when specifying physical media for required throughput over a given run length.
- ✗
Switch port density
Why it's wrong here
Switch port density determines how many devices can connect, not latency, jitter or loss affecting voice quality. It is tempting because VoIP endpoints need switch ports, and would be correct when planning cabling and access-layer capacity for a large handset rollout rather than ensuring call quality.
- ✗
Firewall throughput
Why it's wrong here
Firewall throughput governs inspection capacity for permitted flows, not the latency, jitter and packet loss that determine voice quality. It is tempting because firewalls sit in the voice path, and would be correct when sizing inspection capacity for concurrent sessions rather than guaranteeing call quality.
- ✓
Switch QoS settings
Why this is correct
QoS settings on switches classify and prioritise voice traffic, giving latency-sensitive RTP packets precedence over bulk data. This queuing mechanism prevents jitter and packet loss that degrade call quality, which raw bandwidth alone cannot guarantee.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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