[OpenSIPS-Users] Transfer issue

[Iñaki Baz Castillo]

El Viernes, 23 de Octubre de 2009, Peter den Hartog escribió:
> yeah i understand that, but why is it sending this refer to the sip trunk?
>  i mean..
> 
> it's an outside call going to a local extention, i want to transfer from 1
> local extention to another, so why isn't my opensips doing this refer?

Sorry but you don't seem to understand how a REFER transfer works:

1) Your PSTN provider sends an INVITE to your proxy (opensips).
2) OpenSIPS routes the call to user1.
3) User1 answers the call and so.
4) User1 wants to transfer the call to user2.
5) User1 sends a REFER to *the PSTN provider* (through OpenSIPS as any in-
dialog request).
6) The PSTN provider accepts the refer so *initiates* a new call to user2.

Of course point 5 will NEVER work with a PSTN provider (and shouldn't work at 
all!). This is why PBX/B2BUA do exist: to enable PBX features.

If you just have a proxy and receive calls from a PSTN you could NEVER 
transfer that call to other user.

Having a PBX/B2BUA the sceario changes and allows transference. An example 
scenario:

1) Your PSTN provider sends an INVITE to your PBX (B2BUA).
2) The PBX generates a *new* INVITE (a different dialog) to OpenSIPS.
3) OpenSIPS routes the call to user1.
4) User1 answers the call.
5) User1 wants to transfer the call to user2.
6) User1 sends a REFER to *the PBX* (through OpenSIPS as any in-dialog 
request).
7) The PBX  provider accepts the refer so *initiates* a new call to user2.
8) The PSTN provider didn't realize, at all, about the transference.




-- 
Iñaki Baz Castillo <ibc at aliax.net>