[OpenSIPS-Users] B2BUA REFER scenario

[Tony Ward]

Hello, 
I currently have this configuration:
PSTN <====> SIP/ALG Router <====> OpenSips 1.10 <====> IVR 
OpenSips has a single IP on the private network.

I have configured opensips using top hiding in the dialog module and it
works fine for calls to ptsn  and calls from pstn.
I have also configured opensips using B2BUA top hiding and it also works
fine for calls to ptsn  and calls from pstn.

Now I want to test B2BUA REFER scenario (where calls from PSTN are
answered by IVR, then IVR does a REFER to another PSTN number).

When the IVR sends REFER the call is dropped after .6 seconds.  The flow
that I've seen in the trace is below:
PSTN			     opensips			IVR	
	invite+SDP (Call1) ---->  |	
	<----- Trying (Call1)	|
			    	|	invite+SDP (Call2)-----> 
			    	|	<----- OK+SDP (Call2)
	<----- OK+SDP (Call1)   	|
	Ack (Call1) ---->    	|
			    	| 	ACK (Call2) 	----->

		<Ivr dialog take place here>

				|	<----- REFER (Call2)
	<----- Invite (Call1)	|
			    	|	Accepted (Call2) -----> 
			    	|	BYE (Call2) 	-----> 
	Trying (Call1) ---->           |
	OK+SDP (Call1) ---->       |
	<----- Invite+SDP(Call3)|
			    	|	<----- OK (Call2)
	Trying (Call3) ----->  	|
	OK+SDP (Call1) ----->  	|
	OK+SDP (Call1) ----->  	|

		<0.6 seconds elapse here>

	Bye (Call1) ----->	|
	<----- OK (Call1)   	|
	<----- Cancel (Call3)   	|
	OK (Call3) ----->	|
	Req Termd (Call3) ----->|
	<----- Ack (Call3)   	|

It looks as though the PSTN times out waiting for an ACK after sending
OK+SDP(Call1) a couple times and then waiting .6 seconds.
The question is - what should the flow look like?  According to this
post:  http://lists.opensips.org/pipermail/users/2012-April/021352.html,

things appear to be working as expected up to the point where we receive
Trying (Call3).  Should I be seeing the OK+SDP from call 3 next?
I'd like to troubleshoot further but I'm not sure where to look.

Thanks!
Tony