[OpenSIPS-Users] Prevent re-INVITE to T.38

[Ovidiu Sas]

Well, then your out of luck here.
Even if there's no SDP in ACK, should be fine.

On the other hand, if one end doesn't support T.38 and the other end
is insisting on it, the call will fail, so you can just drop the call
there.

-ovidiu

On Tue, Mar 11, 2014 at 3:14 PM, Jeff Pyle <jpyle at fidelityvoice.com> wrote:
> By removing the SDP, am I not causing a late-offer behavior?  The B-leg
> would expect an SDP on the ACK from the A-leg (which it's not going to get),
> and the A-leg is going to wonder why its T.38 SDP was answered with, say, a
> G.711 one.
>
> I've yelled at customers for pulling stuff like that.  :)
>
>
>
> - Jeff
>
>
>
> On Tue, Mar 11, 2014 at 2:00 PM, Ovidiu Sas <osas at voipembedded.com> wrote:
>>
>> Then remove completely the SDP.
>> The other endpoint should offer the previous codec.
>> The renegotiation should fail and hopefully the call will still stay on
>> ...
>>
>> Regards,
>> Ovidiu Sas
>>
>>
>> On Tue, Mar 11, 2014 at 1:56 PM, Jeff Pyle <jpyle at fidelityvoice.com>
>> wrote:
>>>
>>> Hi Ovidiu,
>>>
>>> In the case of a pure T.38 SDP offer like this:
>>>
>>> v=0
>>> o=- 1394560461 1394560461 IN IP4 192.168.58.4
>>> s=-
>>> c=IN IP4 192.168.58.4
>>> t=0 0
>>> m=image 16426 udptl t38
>>> a=T38FaxVersion:0
>>> a=T38FaxRateManagement:transferredTCF
>>> a=T38FaxFillBitRemoval:0
>>> a=T38FaxTranscodingMMR:0
>>> a=T38FaxTranscodingJBIG:0
>>> a=T38MaxBitRate:14400
>>> a=T38FaxUdpEC:t38UDPRedundancy
>>> a=T38FaxMaxBuffer:600
>>> a=T38FaxMaxDatagram:200
>>>
>>>
>>> Which codec would I remove?
>>>
>>>
>>> - Jeff
>>>
>>>
>>>
>>> On Tue, Mar 11, 2014 at 1:44 PM, Ovidiu Sas <osas at voipembedded.com>
>>> wrote:
>>>>
>>>> Remove the codec and let the re-INVITE go through.
>>>>
>>>> Regards,
>>>> Ovidiu Sas
>>>>
>>>>
>>>>
>>>> On Tue, Mar 11, 2014 at 1:42 PM, Jeff Pyle <jpyle at fidelityvoice.com>
>>>> wrote:
>>>>>
>>>>> Hi Alexander,
>>>>>
>>>>> To detect the "image" session in the SDP, you are thinking the same way
>>>>> that I am.  The problem I see is how to actually reject the re-INVITE.  If I
>>>>> were to do something like a sl_send_reply("488", "Not Acceptable Here"),
>>>>> that would work in the moment, but the CSeq values would be increased by one
>>>>> on side compared to the other.  That sounds to me like a recipe for problems
>>>>> in future in-dialog transactions (like BYE).
>>>>>
>>>>>
>>>>>
>>>>> - Jeff
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Tue, Mar 11, 2014 at 12:58 PM, Alexander Mustafin
>>>>> <mustafin.aleksandr at gmail.com> wrote:
>>>>>>
>>>>>> Hi, Jeff.
>>>>>>
>>>>>> Maybe stream_exists(regexp) in sipmsgops module will be useful for
>>>>>> you.
>>>>>>
>>>>>> Best regards,
>>>>>> Alexander Mustafin
>>>>>> mustafin.aleksandr at gmail.com
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> 11 марта 2014 г., в 20:07, Jeff Pyle <jpyle at fidelityvoice.com>
>>>>>> написал(а):
>>>>>>
>>>>>> Hello,
>>>>>>
>>>>>> Is there anything I can do at the proxy level to prevent a dialog from
>>>>>> reinviting to to T.38?  I think I could detect the T.38 attributes easily
>>>>>> enough and respond with a 488, although I'm concerned the CSeq values would
>>>>>> be out of sequence for the next transaction that did make it through the
>>>>>> proxy to the far end.  That could cause a problem, no?
>>>>>>
>>>>>> Is this something that requires a B2BUA?  Is it possible from within
>>>>>> the OpenSIPS B2B modules to do SDP inspection of any sort?
>>>>>>
>>>>>>
>>>>>> - Jeff
>>>>>>
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>>>>>
>>>>>
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>>>>
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