[Asterisk-Users] IAX blind transfers

[Michael Puchol]

steve at daviesfam.org wrote:
> 
> On Thu, 14 Apr 2005, Paul Seymour wrote:
> 
> 
>>Just a quick question to ask if blind transfers (via #) are possible?  I
>>have an IAX2 connection to my VOIP provider. In my dial plan I sometimes
>>forward an incoming call back out on IAX, but when this happens I seem
>>to lose the ability to transfer the call.  If the incoming call uses
>>SIP, or the destination uses SIP, transfer works.  I've noticed that in
>>the Asterisk CLI I get message saying "Attempting Native Bridge", but
>>nothing more to indicate whether this failed or succeeded.  I have tried
>>notransfers=yes and notransfers=no in my iax.conf, but this doesn't seem
>>to make a difference, as best I can tell asterisk is staying in the call
>>though, so I'm guessing blind transfers aren't possible?
> 
> 
> If the Asterisk box IS doing IAX native bridging, then the # won't be seen 
> on that box.
> 
> Native bridging is a different thing than transfering.  When an Asterisk 
> box "transfers" the call it actual gets the two remote IAX peers to rather 
> talk directly and sees nothing more of the call (in an IAX trace you'll 
> see TXREQ (transfer request) frames and similar).
> 
> "notransfer" is about enabling and disabling this feature.
> 
> Native bridging is just where chan_iax2.c uses an optimised "quick copy" 
> function to pass frames between the input and output iax connections.
> 
> Native bridging will be done whenever two IAX channels are bridged 
> together and both use the same codec etc.
> 
> There's no config file option to enable or disable it.
> 
> If you don't want native bridging, you need to disable it in chan_iax2.c 
> by undefining BRIDGE_OPTIMIZATION.  If you do that, then your box will 
> probably hear and act on the # transfer request.
> 
> Regards,
> Steve
> 

Hi Steve,

Thanks for that explanation, it's very useful, I'm also having transfer 
problems on IAX2 bridges. In my case, I have a remote * with a couple of 
PSTN lines that are bridged over IAX2 to a local * which in turn handles 
a bunch of SIP phones. When a PSTN call is bridged, the SIP phones 
cannot transfer the call between them, seeing the behaviour explained in 
the first post.

The IAX2 bridge is configured to use gsm, and no trunking. Could you 
confirm if this native bridge disabling could cure this problem too?

Best regards,

Mike