I begin by thanking all of you for the tremendous response to my previous video blog titled Hear Me Out. Based on your feedback I decided to follow up with a sequel picture blog which will introduce us to a variety of tools used to help identify and mitigate VoIP audio issues. As before, in keeping with the brief nature of this picture blog I will let the pictures do the talking and I will provide short explanations where necessary. Please note that the screen shots of the tools I have used are one of many ways to troubleshoot audio issues. There are multiple software/hardware products available today which can automatically provide diagnosis, root cause detection and mitigation to VoIP audio quality issues but we still need to understand some basics of VoIP troubleshooting.
Let us start by taking a look at a few mitigation methodologies that could be used to solve the audio issues I highlighted in my previous video blog. The following table will help us do that.
While troubleshooting IP telephony it is important to capture and analyze IP voice packets from both the sending side as well as the receiving side. This first picture depicts the sending side capture.
And this next picture shows the receiving side capture of the same packets shown in the picture above. Take a look at the highlighted extreme jitter experienced by some of these voice packets. Definitely indicates audio quality problems.
To simulate specific voice load on a network I like to use a SIP Bulk Call Generator to send, receive and record calls with a specific audio file across the network. This next picture shows the statistics of a SIP bulk call generator, namely the number of calls placed, answered, active etc.
Note: I highly recommend using a popular and continuous audio sample like the title theme to the movie Mission Impossible. A popular and continuous tune helps us quickly identify any audio distortions because of our familiarity with that tune.
This next picture shows how call recordings can then be scored for their voice quality. The most popular method is known as Mean Opinion Score (MOS)
In this next picture I have magnified a 20 second audio sample so you can see the co-relation between packet delay and audio distortion.
At the end of the day we are trying to make sure that we deploy best practices to ensure that all the variables which affect voice quality are under a specific threshold. These are listed in the picture below.
In summary there are multiple variables which can affect audio quality issues and educating our consumers to help identify symptoms will result in speedy resolution to their ‘ear’ritating issues.
What tools, software, hardware do you use to troubleshoot your IP network?