[Freeswitch-users] One Way RTP (no NAT) - Freeswitch sends RTP to the remote source port instead of SDP negotiated destination port (with disable_rtp_auto_adjust=true)

[Adelia C.]

We're testing a feature that requires an extra Application Server (B2BUA) on our call path, on the egress side of the call from FreeSwitch. 
With the extra AS, we have only one-way RTP (Caller -> Callee). Without, RTP is fine. 
We narrowed it down to FS enforcing symmetric RTP while AS only works with asymmetric RTP. We cannot change the behavior of the AS at this time.

Call:   

Caller - >NTW -> SBC -> FS -> AS -> SBC -> NTW -> Callee.


RTP streams, as negotiated (SDP):



Caller - > SBCOut:50460
->FSIn:29526 -> FSOut:17818 -> ASIn:8080 -> ASOutB:19040 -> SBCOut:49162  -> Callee (can't hear a thing)


Callee  -> SBCOut:49162
->ASIn:8082 -> ASOut:19000 -> FSIn:17818 -> FSOut:29526 -> SBCIn:50460 -> Caller (good RTP)


 RTP streams, as sent/receiced:

FS negotiates 8080 as the RTP destination to AS in the "caller - > callee" direction. For about .5s, that's how the RTP flows : FSOut:17818 -> ASIn:8080
FS negotiates 19000 as the RTP source from AS in the "callee -> caller" direction. This is how the RTP flows for the duration of the call.: ASOut:19000 -> FSIn:17818
FS switches its RTP stream in the "caller - > callee" direction ~.5s into the call : FSOut:17818 -> ASIn:19000. [ASIn listens on 8080, the caller - > called RTP is dead.]

All this from Wireshark trace.

I tried the following, with no success:

1. Added to MyFSApp.xml and dialplan\public.xml:
    <action application="set" data="disable_rtp_auto_adjust=true"/>
    <action application="set" data="rtp_manual_rtp_bugs=accept_any_packets"/> 
Restarted, FS, same result.

2. Commented out 
<param name="ext-rtp-ip" value="auto-nat"/>
<param name="ext-sip-ip" value="auto-nat"/>
<param name="use-rtp-timer" value="true"/>
Restarted, FS, same result.

3. Started FS with -nonat, then nonatmap
Same result.

Other info : 
- Our App on FS runs in B2BUA mode, doesn't proxy the call. We answers the incoming leg before initiating the outgoing leg. I can attach the Wireshark is I didn't provide enough info - I have both FS and AS pcaps.
- Our FS code about 2 weeks old.

What else can I try? Any other settings I can enable/disable? Can I enable extra RTP logs on FreeSwitch for debug? 

Thanks,
A.C.
  		 	   		  
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