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

[Jeff Pyle]

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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>>>
>>>
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>>> http://www.voipembedded.com
>>>
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>>
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>
>
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> http://www.voipembedded.com
>
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