Cisco 7970G Administration Guide - Page 258

Monitoring the Voice Quality of Calls Chapter 9 Troubleshooting and Maintenance 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: • G.711 codec gives 4.5 score • G.729A/ AB gives 3.7 Note • CVTQ does not support wideband (7 kHz) speech codecs, as ITU has not defined the extension of the technique to wideband. Therefore, MOS scores that correspond to G.711 performance are reported for G.722 calls to allow basic quality monitoring, rather than not reporting an MOS score. • Reporting G.711-scale MOS scores for wideband calls through the use of CVTQ allows basic quality classifications to be indicated as good/normal or bad/abnormal. Calls with high scores (approximately 4.5) indicate high quality/low packet loss, and lower scores (approximately 3.5) indicate low quality/high packet loss. • Unlike MOS, the Conceal Ratio and Concealed Seconds metrics remain valid and useful for both wideband and narrowband calls. 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 Table 9-5 for general troubleshooting information: 9-24 Cisco Unified IP Phone 7970G/7971G-GE Administration Guide for Cisco Unified Communications Manager 6.1 OL-14626-01