Chapter 8 Troubleshooting and Maintenance

Monitoring the Voice Quality of Calls

To use the metrics for monitoring voice quality, note the typical scores under normal conditions of zero packet loss, and use the metrics as a baseline for comparison.

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

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 Table 8-5for general troubleshooting information:

Table 8-5

Changes to Voice Quality Metrics

 

 

 

Metric Change

 

Condition

 

 

MOS LQK scores

Network impairment from packet loss or high jitter:

decrease 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

•

Check to see if the phone is using a different codec than expected (RxType and TxType).

decrease significantly

•

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

 

 

 

 

 

Conceal Ratio and

•

Network impairment from packet loss or high jitter.

Conceal Seconds

 

 

increase significantly

 

 

 

 

 

Conceal Ratio is near or

•

Noise or distortion in the audio channel such as echo or audio levels.

at zero, but the voice

•

Tandem calls that undergo multiple encode/decode such as calls to a mobile network or

quality is poor

 

 

 

calling card network.

 

 

 

 

 

• Acoustic problems coming from a speakerphone, handsfree mobile phone or wireless headset.

 

 

Check packet transmit (TxCnt) and packet receive (RxCnt) counters to verify that voice packets

 

 

are flowing.

 

 

 

 

Voice quality metrics do not account for noise or distortion, only frame loss.

 

Cisco Unified IP Phone 7960G/7940G Administration Guide for Cisco Unified Communications Manager 7.0 (SCCP)

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Cisco Systems 7960G, 7940G manual Metric Change Condition
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7960G, 7940G specifications

Cisco Systems has long been a leader in creating innovative networking and communication solutions. Among their range of Voice over IP (VoIP) phones, the Cisco 7960G and 7940G stand out as robust, versatile devices that cater to the needs of modern businesses. Released in the early 2000s, these models respectively combine functionality, ease of use, and key features tailored for effective communication.

The Cisco 7960G is a high-end model designed for users who demand advanced features and functionalities. It comes with a large backlit LCD display that not only enhances visibility but also provides easy navigation through various options. The phone supports up to six lines, allowing users to manage multiple calls effortlessly. Its user-friendly interface includes programmable feature buttons and a 10/100 Ethernet switch, enabling seamless integration into existing networks.

On the other hand, the Cisco 7940G is a more basic model designed for users who require essential features for their business communications. It includes a monochrome LCD screen and supports a maximum of two lines. Despite its simplicity, the 7940G is equipped with several key features such as integrated speakerphone and mute options, making it ideal for day-to-day communication needs. Both models support Power over Ethernet (PoE), eliminating the need for separate power adapters and ensuring a cleaner, more organized workspace.

In terms of technologies, both the 7960G and 7940G leverage the Session Initiation Protocol (SIP) for signaling and media exchange. They also support secure communication through protocols like Secure Real-time Transport Protocol (SRTP) and Transport Layer Security (TLS). This ensures that businesses can engage in confidential conversations without the risk of interception.

The characteristics that make these models appealing include durability, ease of configuration, and reliability. Organizations can benefit from Cisco’s reliable support and regular updates, ensuring that their communication infrastructure remains robust and secure. With features designed for scalability, both phones can easily integrate into larger systems while maintaining high call quality.

In summary, Cisco’s 7960G and 7940G VoIP phones are exemplary devices that cater to a variety of business communication scenarios. With their blend of functionality, support for essential technologies, and reliable performance, they continue to serve organizations effectively in an increasingly interconnected world. Whether used in a bustling office or as part of a dynamic telecommunications strategy, these models offer excellent value and performance.
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