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Transcript for this video

Lets test the voice quality of a new Voice over IP telephone when conditions are less than perfect.

Our overall strategy will be to take the incoming voice traffic, classify it into its own stream and then apply various impairments to the voice traffic.

All other traffic will be unaffected.

Let's start with the filter map.

On the “Filter Map” screen, we will select the second item from the bottom.

We know that most VoIP packets are less than 256 bytes long, and we will ignore the quality of surface bits.

We recognize that there are other types of traffic that fit this description, such as Domain Name System traffic (DNS).

For the purposes of this exercise, we will allow other types of traffic to be impaired along with the voice traffic.

We select “voip_256_qos_ignore” and we are going to put all the traffic through band 2 in both directions.

By the way, you can create your own custom filter for your own VoIP traffic by going to the filter inventory and selecting “new.”

Click on the submit button at the bottom of the page.

The Mini Maxwell configuration updated successfully.

Now we will click on the “Bands/Impairments” button in order to apply impairments to our voice traffic.

Pick the “band 2” tab.

We will start with a simple example.

The first impairment is the “delay & jitter” impairment.

We will add a constant delay of 100ms in each direction.

This is a typical delay for an internal VoIP phonecall.

Now click on the submit button.

Now you can hear how voice quality is affected when network traffic is delayed.

Another common occurrence on networks is jitter.

We will change our “fixed delay” impairment to a “jitter” impairment. Jitter is a variation in delay.

We add 50ms of variation. We will also use the “Normal” distribution.

This means that each packet will be randomly delayed between 50ms and 150ms.

Click on the “Submit” button.

You can now listen to how your VoIP phone handles jitter, a very common occurrence on networks.

We will discuss more complex jitter scenarios on another video.


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