In this blog, I will discuss about our NetFlow and VOIP add-ons for OpManager and how they help in isolating VOIP degradation due to bandwidth consumption and QoS configuration issues. If you are new to OpManager, please visit this link for more information. VOIP add-on relies on Cisco IPSLA to collect QoS metrics. The Cisco IOS IP Service Level Agreements(SLAs) is a Cisco technology use active monitoring to generate traffic in a continuous, reliable, and predictable manner, thus enabling the measurement of network performance and health. Please visit this link to know more on Cisco IP SLA.
As discussed in previous blog, we rely extensively on performance data like packet loss, delay, jitter and the Mean Opinion Score (MOS) to define QoS policies. Now OpManager with Netflow and VOIP add-on gives you a single comprehensive console to correlate all these parameters and helps reduce voice quality issues instantaneously.
VOIP and NetFlow dashboard
OpManager add-on family includes NetFlow and VOIP add-ons for increased visibility into network performance data. VOIP dashboard displays all performance centric information like packet loss, delay, jitter and the Mean Opinion Score (MOS). Network administrators identifies the problematic sites based on the MOS. MOS is a function of codec used for voice communication, jitter, packet loss and delay. Sites having the poorest MOS scores are hit with high jitter and packet loss. The following is the general MOS rating scheme for voice traffic.
|
Mean Opinion Score |
Quality |
Impairment |
|
5 |
Excellent |
Imperceptible |
|
4 |
Good |
Perceptible but not annoying |
|
3 |
Fair |
Slightly annoying |
|
2 |
Poor |
Annoying |
|
1 |
Bad |
Very annoying |
The following use cases helps us to understand the functionality of both the add-ons.
1. Poor voice quality due to incorrect configuration of backup process:
Following is a screenshot of a VOIP dashboard on OpManager. Here we can see a bad call with high jitter and latency.
MOS for a voice call with Jitter, Packet Loss, and delay.
Now the administrator can see into the bandwidth usage pattern of the particular link which connects to the remote site in the same page. Using the detailed bandwidth reports like top applications and conversations, generated using NetFlow add-on, network administrator can quickly identify the root cause of the VOIP degradation. In the screenshot, we can see there is a backup process occupying most of the bandwidth during the period when performance degradation happened.
Voice degradation due to backup process
Based on the observations the backup process is rescheduled for non-business hours and this helps increase the voice quality during business hours.
2. Using NetFlow add-on – CBQoS reports to identify traffic drops:
Another angle to investigate this VOIP degradation is examining the QoS policies defined at the router level. Here we can use the CBQoS reporting ability in NetFlow add-on, to find drops in voice traffic due to insufficient bandwidth allocation or lack of priority routing to the voice class.
In the following screenshot, CBQoS graph gives you the pre and post policy metrics including the drop percentage for each class. Using this information, the administrator finds traffic drop in VOIP class and so can raise the VOIP priority to route the voice traffic in best effort.
Drop in voice traffic – CBQoS report
Hope this helps you understand the functional advantages in using VOIP and NetFlow add-ons with OpManager. Please write to us if you have any questions. Our support email id is netflowanalyzer-support@manageengine.com
Thanks
Raj
cool… I never knew NetFlow Analyzer could help me do this. Good to see the pieces coming together
Tim