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352-001 · Question #428
352-001 Question #428: Real Exam Question with Answer & Explanation
The correct answer is A: buffering at endpoints. Jitter buffers at endpoints absorb variable packet arrival times, smoothing out the delay variation that disrupts VoIP audio quality.
Question
A multinational enterprise company has many branches in the Americas, Europe, and Asia Pacific with headquarters in London. Branch offices use Ethernet (bandwidth range from 1 Mb/s to 10 Mb/s) as access technology to connect to the headquarters and the regional hubs. The company is currently implementing VolP and QoS in all their locations, and they are worried about jitter between their branches and the headquarters. Which option reduces the effect of jitter?
Options
- Abuffering at endpoints
- BCall Admission Control
- Cincrease the bandwidth of the links
- DWRED
Explanation
Jitter buffers at endpoints absorb variable packet arrival times, smoothing out the delay variation that disrupts VoIP audio quality.
Common mistakes.
- B. Call Admission Control limits the number of active calls to protect bandwidth, but it does not smooth out packet arrival time variation for calls already in progress.
- C. Increasing link bandwidth reduces congestion and can lower average delay, but it does not eliminate jitter because variable queuing delays can still occur even on uncongested links.
- D. WRED is a congestion avoidance mechanism that proactively drops lower-priority packets to prevent queue buildup, but it does not buffer or reorder packets to compensate for jitter at the endpoint.
Concept tested. VoIP jitter buffer as QoS mitigation
Reference. https://www.cisco.com/c/en/us/support/docs/voice/voice-quality/26505-qos-voip.html
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