Hello!

An extension registered at asterisk 13.23 initiates an external call (pjsip). After the Invite, the callee (-> ISP) sends a

100 Trying
183 Session Progress (*without* SDP)

Asterisk now sends to the extension:

183 Session Progress (*with* SDP)
183 Session Progress (*with* SDP) (really two times)

The callee meanwhile sends

180 Ringing (*without* SDP)

which is “forwarded” by Asterisk to the extension with

180 Ringing (*with* SDP)

The problem: The extension doesn’t create a ringback locally, because it most probably expects it to be sent by the callee – but the callee doesn’t send anything (not surprising, because there has been no SDP).

Or should Asterisk create the ringback (Asterisk doesn’t send any RTP package)? Or should the phone create the ringback itself because there is a 180 Ringing (even if it contains SDP)?

I’m wondering: Why does Asterisk create a 183 to the extension containing SDP if the callee didn’t provide any SDP?

So many questions … . Could somebody please shine some light on it? What’s going wrong here?

Thanks, Michael

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