210-065 · Question #387
An engineer is troubleshooting call quality issues between two sites. On an active voice call, the call statistics on the IP phone show that the max jitter is 100 ms. Which option is the maximum…
The correct answer is D. 50 ms. Cisco's QoS guidelines set 50 ms as the maximum acceptable one-way jitter for high-quality voice calls, as this is the upper limit that jitter buffers can compensate for without audible degradation.
Question
An engineer is troubleshooting call quality issues between two sites. On an active voice call, the call statistics on the IP phone show that the max jitter is 100 ms. Which option is the maximum amount of jitter that the engineer can allow and still expect to maintain a high-quality audio call?
Options
- A5 ms
- B10 ms
- C30 ms
- D50 ms
How the community answered
(15 responses)- A7% (1)
- B7% (1)
- D87% (13)
Why each option
Cisco's QoS guidelines set 50 ms as the maximum acceptable one-way jitter for high-quality voice calls, as this is the upper limit that jitter buffers can compensate for without audible degradation.
5 ms is an impractically tight threshold that no real-world WAN path reliably achieves and is not the Cisco-recommended maximum jitter value for voice.
10 ms is well below the Cisco-recommended 50 ms ceiling and would incorrectly classify calls with perfectly acceptable jitter levels as failing quality standards.
30 ms is the preferred target for optimal voice quality but is not the maximum acceptable threshold - calls with jitter between 30 ms and 50 ms can still deliver high-quality audio.
Cisco's QoS design guidance specifies that one-way jitter must not exceed 50 ms for acceptable voice quality, because IP phone and gateway jitter buffers are sized to absorb up to this amount of inter-packet delay variation - the 100 ms measured in this scenario exceeds that ceiling and directly explains the reported call quality issues.
Concept tested: VoIP jitter threshold and QoS voice quality requirements
Source: https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND/QoS-SRND-Book/QoSVoIP.html
Topics
Community Discussion
No community discussion yet for this question.