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.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 9-5for general troubleshooting information:

Table 9-5 Changes to Voice Quality Metrics

Metric Change

Condition

 

 

MOS LQK scores decrease

Network impairment from packet loss or high jitter:

significantly

• 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.

 

 

MOS LQK scores decrease

• Check to see if the phone is using a different codec than

significantly

expected (RxType and TxType).

 

• Check to see if the MOS LQK version changed after a firmware

 

upgrade.

 

 

 

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Cisco Systems 7970G, 7971G-GE manual Troubleshooting Tips, Metric Change Condition
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7970G, 7971G-GE specifications

The Cisco Systems 7971G-GE is a sophisticated IP phone designed for enterprise communication, offering a range of features that enhance productivity and collaboration. As part of the Cisco Unified Communications portfolio, this phone is known for its impressive technology and reliable performance.

One of the main features of the 7971G-GE is its high-resolution color display. The 5-inch LCD screen provides users with a visually appealing and intuitive interface, allowing for easy navigation through menus and contacts. The phone supports up to six lines, making it ideal for users who require multiple lines for simultaneous calls. Users can effortlessly manage calls with the ability to switch between lines and access important call features like hold, transfer, and conference calling.

In terms of audio quality, the Cisco 7971G-GE is equipped with high-definition voice technology. This feature ensures crystal-clear sound during calls, reducing background noise and enhancing the clarity of conversations. The phone also supports wideband audio codecs, enabling a richer voice experience that is particularly valuable in business environments.

The phone is designed with user convenience in mind. It offers programmable buttons that can be customized to suit individual needs, allowing easy access to frequently used functions or contact lists. Additionally, the presence indicator feature lets users see the availability of their colleagues in real-time, promoting more effective communication and collaboration.

Networking capabilities are another strong point of the Cisco 7971G-GE. The phone supports both Power over Ethernet (PoE) and standard Ethernet connectivity. This enables easy deployment without the need for additional power outlets. Moreover, the device is compatible with various Cisco communication platforms, integrating seamlessly with existing Cisco infrastructure, which is essential for businesses looking to upgrade their communications systems.

Security is a crucial consideration for modern enterprises, and Cisco addresses this with robust encryption features that protect voice and video calls. The phone supports secure signaling and media encryption, ensuring that sensitive conversations remain confidential.

Overall, the Cisco Systems 7971G-GE is a feature-rich IP phone that combines advanced technology with user-friendly design. Its high-definition audio, customizable features, and seamless integration with Cisco networks make it a popular choice for businesses seeking to improve their communication systems. With its reliability and performance, the Cisco 7971G-GE continues to support effective collaboration in an increasingly connected world.
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