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How to extract a single voip call from a pcap with many using the display filter.

asked 05 Mar '15, 03:47

tarmongaidon's gravatar image

accept rate: 0%

edited 18 Mar '15, 07:33

What's wrong with clicking 'Prepare filter' in the first dialog?

(05 Mar '15, 08:15) Jaap ♦

Absolutely nothing Jaap, that's a better way of getting the call ID. Is there an easier way of getting the ssrc value?

(06 Mar '15, 02:40) tarmongaidon

Could you please the text of your question as an answer to the question, and then edit the text of the question as "How do I display one VoIP call in a capture with multiple calls?" or something such as that, so that the actual answer shows up as an answer and this shows up as an answered question; that better fits the way Q&A sites are intended to be used, and would allow alternative answers (e.g., if MATE could be somehow used for this).

(06 Mar '15, 18:12) Guy Harris ♦♦

Hi All,

Being a VoIP support tech there have been numerous occasions where I've had to extract just one call from a pcap with 100's of calls.

This is not any easy task. After a lot of googling around I haven't found this process documented yet.

Having spent a couple of hours on it I've found a way of using the display filter to filter for the ssrc and Call-ID values and thought I'd share this with you guys:

1 - Open wireshark and find the desired call by navigating to Telephony -> VoIP Calls. Then click the Flow button to get the call flow.

alt text

2 - Click on the Invite (or any other SIP message) and drill down to the message header and copy the call-ID value. Alternatively you could click 'prepare filter' in the above dialog to automagically prepare a filter with the Call-ID.

alt text

3 - Select an RTP packet on each stream and note down the Synchronization Source identifier (ssrc) value for all streams.

alt text

4 - Use the following display filter and enter the values copied from the previous steps (or modify the existing filter if you clicked 'prepare filter' above:

rtcp.senderssrc==[ssrcvalue1] or rtcp.senderssrc==[ssrcvalue2] or rtp.ssrc==[ssrcvalue1] or rtp.ssrc==[ssrcvalue2] or sip.Call-ID==[Call ID]

5 - Navigate to File -> Export Specified Packets and make sure that the 'Displayed' radio button is highlighted, give it a file name and save the file.

Note that you might need to decode the UDP packets as RTP when you open the file on another workstation.

I hope this saves you guys some time, I've been trying to figure this out on and off for a while now. Any suggestions on making the process less of a PITA or better are welcome.

Peace out :)

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answered 18 Mar '15, 07:32

tarmongaidon's gravatar image

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question asked: 05 Mar '15, 03:47

question was seen: 40,918 times

last updated: 18 Mar '15, 07:33

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