This could also be due to serial forking by a proxy upstream, leading to a conflicting blizzard of different progress indications from various gateways. If you can get a capture of such a scenario and indeed find a 183 -> 180 dynamic, I'd be curious to take a look at it. Of course, there's no reason a lightweight pass-thru B2BUA in an SBC couldn't behave in a way that leads to the same result. -- Alex On Tue, Aug 20, 2019 at 12:37:19PM -0400, Pete Eisengrein 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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-- Alex Balashov | Principal | Evariste Systems LLC Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free) Web: http://www.evaristesys.com/, http://www.csrpswitch.com/