"SDP 200 OK" with Cseq "INVITE"

Asterisk Asterisk SIP
1

Hey guys!

Recently my sip trunk provider (Net2Phone) signaled a “conflicting” behavior where Asterisk would be responding to your INVITE with another INVITE.
At the time I explained that it is a standard Asterisk behavior and highlighted that the response is a valid “200 OK” and not a Request INVITE and that only “Cseq” presents the INVITE information.

I would like to know if it is possible to change this information in the SDP “200 OK” in order to avoid early and mistaken reports from operators.

Below is a print of the sip flow:

image
image1893×582 43.5 KB

2

Change the CSeq in that scenario? No. That would violate the SIP specification, and could potentially (likely) cause failure.

3

Indeed, as I imagined!

I brought this case just for better understanding and as an example for the community.

Thank you very much @jcolp for your collaboration!
Know that I greatly admire your knowledge of Asterisk and follow your work.

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4

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