Troubleshooting Tips - Cisco 7975G Administration Manual

Chapter 9 Troubleshooting and Maintenance
A Conceal Ratio of zero indicates that the IP network is delivering frames and packets on time with no
loss.

Troubleshooting Tips

When you observe significant and persistent changes to metrics, use
troubleshooting information:
Table 9-5
Metric Change
MOS LQK scores
decrease significantly
MOS LQK scores
decrease significantly
Conceal Ratio and
Conceal Seconds
increase significantly
Conceal Ratio is near or
at zero, but the voice
quality is poor.
Voice quality metrics do not account for noise or distortion, only frame loss.
Note
OL-12642-01
Changes to Voice Quality Metrics
Condition
Network impairment from packet loss or high jitter:
Average MOS LQK decreases could indicate
•
widespread and uniform impairment.
Individual MOS LQK decreases indicate bursty
•
impairment.
Cross-check with 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.
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.
Cisco Unified IP Phone 7975G Administration Guide for Cisco Unified Communications Manager 6.0
Monitoring the Voice Quality of Calls
Table 9-5 for general
9-19