Cisco Systems 7970G manual Troubleshooting Tips

Chapter 9 Troubleshooting and Maintenance

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:
	• G.711 codec gives 4.5 score
	• G.719A/ AB gives 3.7 score
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 9-4for general troubleshooting information.

	Cisco Unified IP Phone Administration Guide for Cisco Unified CallManager 5.1 (SIP), Cisco Unified IP Phones
9-22	OL-11524-01