Cisco 7906G Administration Manual page 228

Monitoring the Voice Quality of Calls
It is important to distinguish significant changes from random changes in metrics.
Significant changes are scores that change about 0.2 MOS or greater and persist
in calls that last longer than 30 seconds. Conceal Ratio changes should indicate
greater than 3 percent frame loss.
MOS LQK scores can vary based on the codec that the Cisco Unified IP Phone
uses. The following codecs provide these maximum MOS LQK scores under
normal conditions with zero frame loss:
•
•
A Conceal Ratio of zero indicates that the IP network is delivering frames and
packets on time with no loss.
When you observe significant and persistent changes to metrics, use
general troubleshooting information:
Table 9-4
Metric Change
MOS LQK scores decrease
significantly
MOS LQK scores decrease
significantly
Cisco Unified IP Phone 7906G and 7911G Administration Guide for Cisco Unified CallManager 5.1
9-22
G.711 codec gives 4.5 score
G.719A/ AB gives 3.7 score
Changes to Voice Quality Metrics
Chapter 9 Troubleshooting and Maintenance
Condition
Network impairment from packet loss or
high jitter:
Average MOS LQK decreases could
•
indicate widespread and uniform
impairment.
Individual MOS LQK decreases
•
indicate burst 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.
Table 9-4 for
OL-11515-01