Wireshark-users: [Wireshark-users] Interpretting a VoIP call
Hello,
for my school project, I decided to analyze a VoIP call using wireshark but there are some things that are not clear to me.
below, I am always talking about RTP packets
first of all, in a conversation, I expect that the initiator and the receiver take turns talking. Therefore, I expected to see that when the initiator is sending packets (talking), the receiver is listening (not sending packets), but that is not the case in my Wireshark captures.
What I see is that the receiver generally sends packets continuously at a frequency of 1 packet every 20ms.
On the other hand, the receiver is simultaneously sending packets in a different pattern. The receiver sends 4 to 5 packets almost at instantly (
0.0x ms between each packet), then it waits 80 to 100ms during which it receives 4 to 5 packets from the initiator, then it sends another burst of 4-5 packets.
So my questions so far are
-Why do initiator and receiver send packets simultaneously?
-Why do initiator send packets in different patterns? (20ms vs a burst of packets followed by a wait)
The answer to my first question, I suspect, would be noise, or synhetic noise was introduced into the conversation on purpose (comfort noise) but I am not sure about this.
My final question is:
-If it is true that the reasons initiator and receiver send packets at the same time, why, then, are there times that they do not send packets at the same time? (in one conversation, the initiator is talking for an extensive period of time during which the receiver sends no packets)
