A few doubts w.r.t RTCP packets...

Archived from groups: comp.dcom.voice-over-ip (More info?)

Stephen Regan wrote:
> Hi,
>
> Let me give a brief description of my project before I put forth my
> doubts. I am developing a project to develop a VoIP quality monitoring
> software that resides in a dedicated machine and captures the RTCP
> packets for voice quality measurement. The initial version will not
> involve in voice recording and other stuffs. Just plain RTCP packet
> capture and decoding... Ok. Now, to my queries..
>
> Is'nt it mandatory for all VoIP endpoints to send RTCP packets when
> they are engaged in a call? Looks like SJPhone does not send them. Is
> this quite natural or is it a limitation in SjPhone. What are the
> consequences of this.
>

I don't think it is mandatory. I may be wrong.

> Next, I tried with Window Messenger. Messenger does send RTCP packets
> at regular intervals and I am able to recieve them properly. But, I am
> able to receive the packet only from the machines that are involved in
> the conversation. How can I get them from a separate machine that is
> not actively involved in the call? I think RTP/RTCP spec does allow
> such third party devices/applications to decode rtcp information. How
> do I enable this??
>

How so you capture the packets on the same machine and how are you
attempting to capture them on a third machine? How is that third machine
connected to the network ?

> Any pointers are greatly appreciated.
>
> With Regards,
> Stephen Regan.
>

Archived from groups: comp.dcom.voice-over-ip (More info?)

I am not able to see my reply. Hence reposting it :-(. Plz ignore this
if its duplicated.

I used Ethereal to capture the packets. In the first case, Ethereal was
running in one of the endpoint machine. In the second case, I tried
running ethereal in the machine in which SIP Server was running, as
well as a machine that is not involved in the VoIP call, except being
in the same network as that of the other machines.

BTW, all machine are in the same network and are connected to the same
switch.

Archived from groups: comp.dcom.voice-over-ip (More info?)

Yaser,

Do you mean to say all the RTCP packets will be broadcasted to all the
machines in the network. Any way, I will check its getting dropped in
the switch.

Stephen Regan.

Archived from groups: comp.dcom.voice-over-ip (More info?)

SteveRegan wrote:
> Yaser,
>
> Do you mean to say all the RTCP packets will be broadcasted to all the
> machines in the network. Any way, I will check its getting dropped in
> the switch.
>
> Stephen Regan.
>

No, In the old days when Ethernet used a coax cable or used hubs, any
packet on the LAN was available for any machine to pickup. Hence you
could use sniffers to listen to communications between 2 machines using
a 3rd one. These days Ethernet switches ensure that packets only travel
between 2 ports and do not send a packet on a port unless it need to. So
a third machine will not be able to pick up packets not addressed to it.
I am talking about all ethernet packets (at the physical layer.

Yaser