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FreeSWITCH Version: 1.10.3

I was hoping that someone maybe able to help me.

Intermittently on inbound calls from the our sip provider we are sending a empty RTP packet back to the provider. After doing some investigation, it happens when FreeSWITCH receives RTCP from another FreeSWITCH instance.

<SIP Provider> <----> <FreeSWITCH 1> <----> <FreeSWITCH 2>

FreeSWITCH 1 receives an inbound call from an external caller and is acting as a B2BUA in front of FreeSWITCH 2. Once the call is answered by FreeSWITCH 2 the RTP streams are setup and work in both directions.

FreeSWITCH 2 sends all the RTP packets to FreeSWITCH 1 but FreeSWITCH 1 is sending a RTP packet with an empty payload to the SIP provider, on either side of this empty RTP packet there is RTP with the MARKER bit set.

Adjusting the below RTCP timers on FreeSWITCH 2 affects the frequency of the problem on FreeSWITCH 1.

<!-- enable rtcp on every channel also can be done per leg basis 
     with rtcp_audio_interval_msec variable set to passthru to pass 
     it across a call -->
<param name="rtcp-audio-interval-msec" value="5000"/>
<param name="rtcp-video-interval-msec" value="5000"/>

Honestly, I am having a real hard time wrapping my head around why this is happening and only for incoming calls, I am not sure if this is bug or if haven't set something correctly.

If anyone is able to help or point me in the right direction that would be amazing?

aturner
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  • Interesting behavior, is it breaking anything? Why do you care, basically? – os11k Jul 21 '20 at 11:56
  • @os11k - On most calls its barely audible but it is still there. If we are interacting with a particular provider the problem gets amplified which then leads to not being able to bad call quality. – aturner Jul 21 '20 at 13:15
  • Ok, I think I got a point, have you tried to switch off RTCP at all? – os11k Jul 21 '20 at 14:30
  • @os11k How? I have search for this and it looks like the only 2 parameters you can control I have listed. FreeSWITCH is not documented very well, so if you have some insight that would be great. – aturner Jul 21 '20 at 17:03
  • Hi, if you just remove those parameters, what happens, will it disable RTCP? – os11k Jul 21 '20 at 17:17
  • @os11k interesting, I tried this on `FreeSWITCH 2` in my scenerio but it was still sending RTCP, but I never thought about making sure it was switched off on `FreeSWITCH 1`. I will give it a go and let you know the results. – aturner Jul 21 '20 at 21:46
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    @os11k disabling it on FreeSWITCH 1 seems to work not sure why this was enabled! – aturner Jul 22 '20 at 15:58
  • I think I am going to raise it as a bug anyway, because having this switched on surely shouldn’t cause a problem like this. – aturner Jul 22 '20 at 15:58
  • Great, I'm happy that you got this fixed! – os11k Jul 22 '20 at 16:51

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