Ok, welcome back. In our next segment
we will talk about analyzing poor voice quality.
So what consitutes poor quality?
Very simply, if you pick up the phone and you hear
be very teeny or hollow or you hear static,
or you hear anything other than a clear, crisp
quality phone call, then that would constitute poor quality.
As we've mentioned earlier, your data network needs to be pristine.
And quite frankly, when you have issues with voice,
a lot of times, the knee jerk reaction is
to start looking into possible issues with the voice configurations in the voice system.
But in reality, the data network also plays very closely.
So, I can give you an example with a port mismatch
from a phone hanging off a PC, a PC hanging off a phone,
an incorrect speed and duplex settings.
Something as simple as that is going to cause you a tremendous issue with quality
and you would have to correct that network data link layer issue
instead of going and starting to mess with QoS and all that other stuff
where really the underlying problem causing the poor quality was in fact the data network.
So just remember that when you're troubleshooting this stuff
that you're going to be looking not only at the voice but also at the data network.
And how can Wireshark help? Well, it can analyze the flow of calls
which we will look at specifically. We can look at the voice calls.
We can reconstruct them in the player and we can take a look and see what's going on.
So, that being said, you will also be able to analyze the response time
in the packets list or the flow graph and use the Expert to really
get an understanding of what could be happening here.
An example, or another example is you may have hair-pinning on a network device.
This may cause voice to only work in a, in a certain direction correctly.
Incorrectly configured QoS causing queuing issues,
that can also play a large role into quality.
Not giving yourself enough of a buffer for voice or prioritizing it incorrectly.
You can experience jitter which comes down to, you can have latency in your network.
That will cause extreme poor quality and you can also see issues with packets being dropped.
And if packets are being dropped or re-transmitted, that can also cause poor quality.
And what's really good is that Wireshark once you place correctly and capture the data
will start to give you some insight into what you can see.
So up on the screen we have the call and to get to that we go to the
telephony menu and we pull voice calls or I should say, VOIP calls.
And if we want to take a look, we can pull up the player
and decode it and then we can see specifically
what exactly was taking place during this call.
Now, why is this helpful?
For those of you that are familiar with audio concepts, this looks very much like as if
you were recording something in pro-tools or a tool of that nature.
It's essentially the same thing and when you look at it, it will tell you over time
exactly what was taking place and, and the quality of the calls.
So obviously, if it's a smaller wave, it's more quiet or less,
and if it's a bigger wave, it's louder or more.
And then you could also suffer from similar things
like if you are clipping or you have distortion, you have enough space or head room.
But a lot of these things come into play
when you pull up the RTP player and you can view these problems.
So, that being said,
just be aware if you're using this player, it's also a security concern.
You can, yes, replay calls that you've captured
which is probably a concern of those who were using the network.
So just be aware that you have to consider security here as well,
because this will be a violation of security if you open up someone's call and listen to it.
So Wireshark, once you captured the data
and then you start putting it into the tools in the telephony menu, such as VOIP calls
will allow you to see the quality of the call.
You'll be able to see some issues with it. You can open up the flow graph.
And you could see if packets are being re-transmitted
or if your underlying protocols are having an issue.
And also with RTP, you can check for,
you could do stream analysis and you could check for out-of-order packets,
or any other issues that are happening with RTP while you're doing your analysis.
And you could look at the RTP stream analysis,
both in forward and reversed direction
and see specifically how many packets,
what the delta is in between the packets,
if you're experiencing jitter, and so on and so forth.
So this could be really helpful and it also provides the summary
for you to give you the max amount of jitter experienced during the call as an example,
and the duration of the call, as well as the max delta.