[Kamailio-Devel] [Kamailio-Users] dialog enhancements #1

Daniel-Constantin Mierla miconda at gmail.com
Wed Feb 4 18:22:39 CET 2009


Hi Inaki,

On 02/04/2009 06:18 PM, Iñaki Baz Castillo wrote:
> 2009/2/4 Daniel-Constantin Mierla <miconda at gmail.com>:
>
>   
>> There is now a new function called dlg_bridge(From, To, outbound_proxy).
>> It can be used to connect From and To users. The mechanism is a simple
>> call transfer scenario.
>>
>> kamailio => INVITE (hold) =>From
>> kamailio <= 200ok <= From
>> kamailio => REFER (To) =>From
>> kamailio <= 200ok <= From
>> ...
>>  From => INVITE ... =>To
>> ...
>> kamailio => BYE =>From
>> kamailio <= 200ok <= From
>>     
>
>
> Hi Daniel, this seems to imitate the mechanism in RFC 3725 (Third
> Party Call Control).
>   
right. There is a script in examples directory, that could be used to 
initiate via MI, however, that is heavy. This new option is one step 
command. Moreover you can do it from config file, e.g., you can get a 
sip options with some special headers and kamailio/openser will connect 
the users.

> Have you considered using initial REFER? It's widely *not* supported
> by common phones, but it would be a first step to improve SIP world :)
>   

You can do initial refer with uac_req_send(). Do you see a potential 
issue doing so?
http://kamailio.org/docs/modules/1.5.x/uac.html#id2467913

> Please read the thread I opened some days ago about "Initial REFER vs
> RFC 3725 (Third Party Call Control)" in SIP-Implementors:
>   https://lists.cs.columbia.edu/pipermail/sip-implementors/2009-January/021485.html
>
> Of course, initial REFER wouldn't work in most of the cases, but I
> have a "custom" solution:
>
> REFER initial-dialog is much cleaner than INVITE of 3PCC, but it's
> usually not allowed by common phones. So a PBX or
> SIP server implementing click2dial could try first a REFER
> initial-request, and in case it receives a negative response (i.e.
> "403 Forbidden" or "501 Not Implemented") the the server could use the
> 3PCC INVITE.
>   
You can do it with kamailio/openser - uac module first, then dialog module.

The admin can even build a list of devices supporting first or second 
option.

> BTW I'm trying to convince some vendors (softphones basically) to
> allow initial REFER (asking permission for the phone user, of course).
>  :)
>   
good luck!

Cheers,
Daniel

-- 
Daniel-Constantin Mierla
http://www.asipto.com




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