[Spce-user] Call forward hangup when having early ACM

[David Pareja | Ingeniero de Red - Telmi Telecom]

Hello,

I am using SPCE mr4.5.4 and I have the following problem: When receiving 
a call from the PSTN and then performing a call forward to the PSTN 
again, if there is Early ACM involved (RFC 3398 Sec. 7.2.5) in the call 
(and therefore the SPCE reveives an 183 Session Progress from the peer 
before the 200 OK to the INVITE), the SPCE responds with a PRACK and 
after that it doesn't respond to the 200 OK corresponding to the INVITE. 
The call is stablished and RTP starts flowing, but the peer keeps 
sending the 200 OK since we didn't respond with the corresponding ACK, 
and after a while (about 20 seconds) it does timeout and the call drops.

When the the call is originated from a subscriber (instead of the PSTN) 
the call forward is performed correctly. Looking at the traces it's like 
the SPCE ignores the 183 and just waits until it receives the 200 OK 
corresponding to the INVITE. In this case, it does respond with the 
usual ACK and the call doesn't drop.

I don't know if there's a known issue regarding this specific aspect of 
the Early ACM with call forwards from and to the PSTN. I already deeply 
searched in the documentation, the internet and the files within the 
SPCE, so I ran out of options. I would greatly appreciate any feedback 
regarding this topic.

Thank you very much.

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