Cisco Cisco MGX-FRSM-HS2 B Serial Frame Service Module Libro blanco

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By navigating to the Interface statistics screen that provides details about packet-related statistics, we find that

Gi1/22, the interface that connects to the core of the campus network, is experiencing serious packet loss.

Figure 5. MOS Quality Chart

As this interface serves all traffic going from and to Building 3 and the rest of the campus including voice traffic, this

is most likely the root cause for packet drops on the RTP stream. The problem in this case was found to be a

hardware defect on the line card that affected the interface. Replacing the card fixed the issue.

This troubleshooting workflow highlights some of the VoIP quality monitoring capabilities and also shows how VoIP

features can be used in combination with other traffic monitoring features on the NAM. In this particular case, we

used interface statistics monitoring in the NAM in Building 3 to isolate the root cause of the problem.

Use Case: Linking Voice Quality to Quality of Service Issues

The NAM GUI offers multiple reports, and depending on the use case, users have the option of using one report or

the other to start their workflow. This use case approaches a problem that is a slight variation of the problem

highlighted in the previous use case. While the previous use case describes a proactive response, this one shows

how to respond rapidly to a problem.

The situation is that the administrator has received a series of complaints in the last few minutes. He realizes that

there is a quality problem but is unsure where in the network it is. In this case, it is useful to narrow down the

problem to a set of calls. Consider the MOS quality pie chart in Figure 5. This chart allows you to vary the time period

being monitored so that you can narrow your analysis into a 5-minute or a 15-minute period. Figure 5 shows that the

overall call quality is less than desirable. There are very few calls that were excellent. This points to a widespread

problem related to voice traffic.

Figure 6. Worst N Calls