[OpenSIPS-Users] Fwd: pre-alerting announcement by modifying the prepaid B2B UA scenario

[Ano Nemo]

Hi all,

I am trying to implement pre-alerting announcement by modifying the prepaid
B2B UA scenario.

If I am not mistaken the default prepaid B2B UA scenario looks as below:


   A Party                    OpenSIPS                          MS       B
Party
1. ----Dialog1:INV+SDP(offer)--->
2.                                ----Dialog2:INV+SDP(offer)---->
3.                                <----Dialog2:200+SDP(answer)---
------------------------------- Bridging
-------------------------------------
4. <----Dialog1:200+SDP(answer)---
5. ----Dialog1:ACK--------------->
6.                                 ----Dialog1:ACK-------------->
------------------------------- Announcement
---------------------------------
7.                                <----Dialog2:BYE---------------
8.
-------------------Dialog3:INV+SDP(offer)-->
9.                                <------------------Dialog3:180
-------------
10                                <------------------Dialog3:200
-------------
11
 -------------------ACK-------------------->
------------------------------- Bridging
-------------------------------------


I am having problems with this behavior because in the prepaid scenario,
the opensips B2B UA will create a leg to B party only after it has received
a BYE from the MS. This means that there has to be a 200 OK before that
which needs to reach the A party and establish media.
The behavior I am aiming for is for the MS to deliver an provisional
response with SDP (183) to A Party and play the announcement. However,
after an 183, I cannot terminate the call from the MS with a BYE and also,
I do not want to generate a 200 OK. But I could generate an error on the MS
(say an 4xx error).
So, the question is, can the scenario xml rules be formulated to make the
B2B UA act on negative response? Is the below possible?

<rules>

  <reply>
    <negative> or <410>

      <rule id= ”1”>
        ...
      </rule>

    </negative> or </410>

  </reply>
</rules>


If not, is there any other way to do this?

Regards,
Ano
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