[OpenSIPS-Devel] Limitations of dialog module

[Bogdan-Andrei Iancu]

Iñaki Baz Castillo wrote:
> 2009/9/10 Bogdan-Andrei Iancu <bogdan at voice-system.ro>:
>   
>>> I agree. The proxy should not discard anything. From UAC2's
>>> perspective the call is there, it only misses an ACK. It will keep
>>> retransmitting the 200 OK, until it decides to give up, unless is an
>>> UAC that was configured to ignore the missing ACK in which case it
>>> will consider that it has the call anyway and will act accordingly.
>>>
>>>
>>>       
>>>> At a moment I had in mind the option for the dialog module to ACK and
>>>> BYE all the sequential 200 OK replies without sending anything to UAC
>>>>
>>>>         
>>> Is this easier to do than to simply forward and make clones of the
>>> dialog?
>>>       
>
> At this point, I would really like to know a *real* case of usage in
> which the UAC receives two (or more) 200 OK and it's useful for it.
> This is:
>
> a) When the second 200 arrives to the proxy, the proxy sends ACK and BYE.
> b) The proxy relays the second 200 to UAC.
>
> I would like to know why b) could be useful for a UAC.
>   
Hmm....practically, I do not know a device making use of multi 200 OK 
replies, but theoretically speaking, I can imagine a media server 
dialling out and being able to keep both 200 OK (and clone the UAC part) 
and handle both calls (as separate calls).

Aside the fact that maybe the UAC has the ability to accept both 200 OK 
and clone the dialog, another aspect is that a proxy is not intelligent  
enough do decide which 200 OK to select and only the UAC is the best 
entity to select which branch to keep.

Of course, all these are theoretical aspects, as personally I never 
found any implementation taking usage of these.

Regards,
Bogdan