Forum Discussion
AudioCodes, Avaya, Media Bypass, and BackToBackBypass offer was declined by Peer
jangliss I don't have a solution, but I'm here to report the similar problem. I don't know if there is Avaya at the other end of this, because that particular call is connected to PSTN network, but the extra INVITE coming the other direction and BackToBackBypass error message are the same symptoms in my case, too. So if anybody else experienced that or found a solution to that, it would be nice to know. Thanks.
I have been scratching my head trying to remember how I resolved this issue and I think it popped up again last week with a different customer and saw the cause. The cause of the problem in both cases was the SBC was sending the private IP address of the SBC to MS Teams.
Take a look at the INVITE and any SDP messages to see what is in the connect body. For example:
INVITE sip:+19725555555@sbc.mydomain.com SIP/2.0
Via: SIP/2.0/TLS sbc.mydomain.com:5061;alias;branch=z9hG4bKac1645244142
Max-Forwards: 67
From: "ALICE RECEPTIONIST" <sip:9725551234@1.2.3.4;user=phone>;tag=1c213210496
To: "User 9725555555" <sip:+19725555555@sbc.mydomain.com>
Call-ID: 123456789@sbc.mydomain.com
CSeq: 1 INVITE
Contact: <sip:1.2.3.4:5060;transport=udp>
Content-Type: application/sdp
Content-Length: 853
v=0
o=BroadWorks 1996477202 1494450535 IN IP4 10.1.2.3
s=-
c=IN IP4 10.1.2.3
t=0 0
a=ice-lite
m=audio 50490 RTP/SAVP 0 100
Notice the "c=IN IP4 10.1.2.3" has the SBC private IP address. This causes Microsoft to reject the call. It must be the SBCs public IP address for Media Bypass.
There has been the introduction of Media Bypass and Local Media Optimizations which allow you to route traffic to internal SBCs and use the private IP addresses of the SBC as well, but the initial invite should still be announcing the public IP (from my testing). More details on that setup here https://docs.microsoft.com/en-us/MicrosoftTeams/direct-routing-media-optimization