Chapter 7 Troubleshooting and Maintenance

Using Voice Quality Metrics

•G.728/iLBC: 3.9 MOS LQK

•G729A/AB: 3.7 MOS LQK

Note

 

• Cisco Voice Transmission Quality (CVTQ) does not support wideband (7 kHz) speech codecs,

 

 

because ITU has not defined the extension of the technique to wideband. Therefore, MOS LQK

 

 

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 or a low packet loss, and lower scores (approximately 3.5)

 

 

indicate low quality or a 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 7-3for general troubleshooting information.

Table 7-3 Changes to Voice Quality Metrics

Metric Change

Condition

 

 

Conceal Ratio and Conceal

Network impairment from packet loss or high jitter.

Seconds increase significantly

 

 

 

Conceal Ratio is near or at zero,

• Noise or distortion in the audio channel such as echo or

but the voice quality is poor.

audio levels.

 

• Tandem calls that undergo multiple encode/decode such as

 

calls to a cellular network or calling card network.

 

• Acoustic problems coming from a speakerphone,

 

handsfree cellular phone or wireless headset.

 

Check packet transmit (TxCnt) and packet receive (RxCnt)

 

counters to verify that voice packets are flowing.

 

 

MOS LQK scores decrease

Network impairment from packet loss or high jitter levels:

significantly

• Average MOS LQK decreases may indicate widespread

 

 

and uniform impairment.

 

• Individual MOS LQK decreases may indicate bursty

 

impairment.

 

Cross-check the conceal ratio and conceal seconds for evidence

 

of packet loss and jitter.

 

 

 

Cisco Unified IP Phone 6901 and 6911 Administration Guide for Cisco Unified Communications Manager 8.5 (SCCP and SIP)

7-12

OL-23874-01

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Cisco Systems 6901 manual Troubleshooting Tips, Metric Change Condition
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6901 specifications

Cisco Systems 6901 is a versatile, compact, and powerful router designed to meet the networking needs of small to medium-sized businesses, as well as enterprise branch offices. This model is part of Cisco's ISR (Integrated Services Router) portfolio, which is known for its capability to integrate multiple services into a single platform, ensuring high efficiency and cost-effectiveness.

One of the main features of the Cisco 6901 is its ability to support advanced routing protocols, including RIP, EIGRP, OSPF, and BGP. This versatility allows for seamless integration into various network architectures, facilitating efficient communication and data transfer across multiple locations. The device is also built to handle high-bandwidth applications, making it an ideal choice for businesses that rely on robust network performance.

In terms of connectivity, Cisco 6901 offers multiple Ethernet ports, supporting both 10/100/1000 Mbps speeds. This ensures that users can connect a variety of devices, ranging from office computers to network printers, all while maintaining optimal network performance. Additionally, the router supports both LAN and WAN interfaces, providing flexibility in deployment options.

Security is a crucial aspect of networking, and the Cisco 6901 does not disappoint in this regard. It comes equipped with advanced security features, including firewall capabilities, intrusion prevention, and VPN support. These features ensure that sensitive business data is protected from unauthorized access, while also providing secure remote access for employees.

Another essential characteristic of the Cisco 6901 is its support for various multimedia applications. The router comes with Quality of Service (QoS) features that prioritize voice, video, and data traffic, ensuring high-quality performance for applications such as VoIP and video conferencing. This is particularly valuable in today's business landscape, where effective communication is critical for success.

The Cisco 6901 is also designed for ease of management and configuration. It features a user-friendly interface that simplifies the setup process, along with comprehensive monitoring tools that enable administrators to keep an eye on network performance and address any issues proactively.

In summary, the Cisco Systems 6901 is a powerful, feature-rich router that combines advanced routing capabilities with robust security measures and multimedia support. Its flexibility, ease of management, and comprehensive service integration make it an excellent choice for businesses seeking to enhance their networking infrastructure. With the Cisco 6901, organizations can achieve efficient communication, secure data exchange, and high-performance network operations, positioning themselves well for future growth.
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