Ethereal-users: Re: [Ethereal-users] question regarding VoIP

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From: Scott Lowrey <slowrey@xxxxxxxxxxx>
Date: Fri, 08 Apr 2005 08:51:44 -0400
If you're sending actual RTP media streams, you can certainly capture the packets as they come in. Analysis of the interpacket timing and point-to-point delay could probably be done with some (very) careful set up.

But Ethereal is not designed for this. QoV involves some complex measurements that go beyond delay and inter-arrival jitter. Also, the endpoints you're using probably incorporate jitter buffers that compensate for some of the packet arrival variations (with latency being the trade-off). Ethereal will not be able to account for this.

Janice Lau wrote:

Another question regarding VoIP..

May i know what are the ways to send and capture the voice files so
that the capture's file can be used to evaluate the VoIP performance?

My supervisor wants me to try this:
Install Ethereal in both PC1 and PC2. Then i should send a fileA from
PC1 to PC2, while Ethereals are in the running mode at that time for
both machine, with filter function on...

From PC1's Ethereal, i then filter out unneccesary packets except the
sent packets ( which are packets of fileA). Same thing does on PC2,
whereby i filter everything but only keep the packets of fileA
received from PC1.
In this case,

a) how do i know that from PC2, the resultant file are purely the
packets of the fileA?
b) is it possible to calculate the delay & jitter by comparing the
packets in PC1 and PC2?

thank you


Janice.

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