[VoiceOps] Ringing problems

Lonny Clark lclarkpdx+voiceops at gmail.com
Thu Sep 5 15:47:57 EDT 2019

Microsoft Lync and Skype for Business platforms do the '183 w/SDP-then-180
response to INVITE' all the time.

When I worked with AcmePacket SBCs, and connecting to MSFT platforms to
PSTN/carrier, for inbound calls we had the SBC change any 183 response to
180 and delete the SDP before sending the response to a PSTN connection.
That way the PSTN only sees 180, and ringback generation from the
originating side continues.

On Tue, Aug 20, 2019 at 9:37 AM Pete Eisengrein <peeip989 at gmail.com> wrote:

> We have recently gotten several complaints about not getting, or severely
> abbreviated ringback. The first few examples we were able to trace back to
> a carrier and believe it is because the call sets up with 183 Session
> Progress w/SDP and <1 second later get a 180 Ringing and the audible
> ringing stops.
> We heard a similar complaint in Europe last with an EU carrier. And again
> today with yet another US (global) provider.
> So, my questions are:
> 1- Anyone else seeing this? If so, what's your workaround/fix?
> 2- Since this is not contained to a single carrier, anyone aware of an SBC
> or softswitch maker recently released code that might be causing?
> Thanks,
> Pete
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