Cisco 8800 Series Maintenance Manual - Page 5

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Maintenance

Voice Quality Troubleshooting Tips

When you observe significant and persistent changes to metrics, use the following table for general

troubleshooting information.

Table 2: Changes to Voice Quality Metrics

Metric Change

Conceal Ratio and Conceal Seconds increase

significantly

Conceal Ratio is near or at zero, but the voice quality

is poor.

MOS LQK scores decrease significantly

MOS LQK scores increase significantly

Note

Voice quality metrics do not account for noise or distortion, only frame loss.

Cisco IP Phone Cleaning

To clean your Cisco IP Phone, use only a dry soft cloth to gently wipe the phone and the phone screen. Do

not apply liquids or powders directly to the phone. As with all non-weatherproof electronics, liquids and

powders can damage the components and cause failures.

Voice Quality Troubleshooting Tips

Condition

Network impairment from packet loss or high jitter.

• Noise or distortion in the audio channel such as

echo or audio levels.

• Tandem calls that undergo multiple

encode/decode such as calls to a cellular network

or calling card network.

• Acoustic problems coming from a speakerphone,

handsfree cellular phone or wireless headset.

Check packet transmit (TxCnt) and packet receive

(RxCnt) counters to verify that voice packets are

flowing.

Network impairment from packet loss or high jitter

levels:

• Average MOS LQK decreases may indicate

widespread and uniform impairment.

• Individual MOS LQK decreases may indicate

bursty impairment.

Cross-check the conceal ratio and conceal seconds

for evidence of packet loss and jitter.

• Check to see if the phone is using a different

codec than expected (RxType and TxType).

• Check to see if the MOS LQK version changed

after a firmware upgrade.

Maintenance