Text2pcap LAPD for Q931 Call Flow

edit

Hi,

After solving this https://ask.wireshark.org/question/33... ,

I need to figure out how to get a nice voice call flow.

Q931 has "Call reference flag":

 - Message sent from originating side
 - Message sent to originating side

But voice call flow doesn't use it. And we get only PSTN =========> nowhere/infinite line :) loosing the exchange between Alice and Bob (network and user)

The direction of the frame (inbound / outbound) does nothing.

So I try to add dummy/custom LAPD header

The are 2 types of LAPD (https://www.tcpdump.org/linktypes.html)

 - 203 DLT_LAPD
 - 177 DLT_LINUX_LAPD

203 DLT_LAPD combining to inboud/outbound direction give Network/user direction. And the voice call flow looks like

   Network ====>  PSTN
                  PSTN  <===== User
   Network ====>  PSTN

177 DLT_LINUX_LAPD give only the same direction no matter what.

I took a look to https://www.tcpdump.org/linktypes/LIN... The "Packet type" seems to be the key. But I failed trying to setup this.

At the end, It would be great to get a call flow with direct echange between User and Network.

Regards Gates