[OpenSIPS-Users] re : Question about B2BUA modules..

jignesh gandhi jhgandhi at yahoo.com
Thu Jul 8 22:30:10 CEST 2010


Hello Anca, 

I have read the b2bua tutorial and have opensips 1.62 installed. 
I am mainly interested in the REFER scenario..

Would the current implementation of the b2bua support the following scenario ?

UE-A calls UE-C and are in a call. UE-C puts UE-A on hold.
UE-C call UE-B and are in a call.  UE-C puts UE-B on hold.

OpenSIPs is not in the path of the original calls.

Before UE-C bridges UE-A and UE-B,  UE-C wishes to get out the middle of the 
call.
One way would be to send a REFER to UE-B .

What if the switch UE-B is connected to does not support REFER ? So I want to do 
the following..

UE-C sends a REFER to SIP-AS ( OPENSIPS ) and upon receipt of the REFER,
using the B2BUA , the SIP-AS would send an INVITE w/replaces and no SDP to UE-B
Upon receiving the 200 Ok w/SDP. the SIP-AS would send an INVITE to UE-A with 
the
SDP received from UE-B's 200 Ok. Upon receiving an ACK from UE-A , SIP-AS would
send an ACK back to UE-B and an INFO message to UE-C and appropriate BYEs.

Below is a simple flow chart... 


UE-C  REFER------------------> OPENSIPS B2BUA(SIP_AS)                         
 UE-B
 
                                            INVITE w/replaces no 
SDP----------------------> 
                                                                                 
      
                                           
 <------------------------------------------200 OK w/SDP(1) 
                                            
                                            INVITE w/ SDP (1)               UE-A
                                            ---------------------------------> 
                                            <----------------200 OK w/SDP 

                                             
ACK---------------------------------------------------> 

                                             ACK--------------------------->
      
         <-------------------------NOTIFY

thanks in advance for your help,
--Jignesh


      
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