[SR-Users] Send UPDATE to inform changes in SDP

Abdul Basit basit.engg at gmail.com
Mon Apr 30 17:57:40 CEST 2018


Well, we faced the same issue of call drop when we play announcement over
183 and then handover call to B party when it come online on voip push
notification.

Telcos have more rigid systems.
Resolution was introducing B2BUA for topo-hiding in the path IMS (A party)
and VoIP service (B & C party).
Check tags of to and from headers of your call traces. That will give you
clue.



--
regards,

abdul basit | p: +92 32 1416 4196 | o: +92 30 0841 1445

On 30 April 2018 at 14:59, Alfonso Pinto <alfonso.pinto at gmail.com> wrote:

> Hi Carsten,
>
> I was thinking about the same, but I need to convince people to add
> another component in the media path, they may be bit reluctant, but the
> idea is great.
> In the meantime, I was able to trick the phones to react how I want
> playing with precondition and 100rel, for now it's acceptable in our
> environment.
>
> Thanks for your answer.
> Regards,
> Alfonso.
>
> On Fri, Apr 27, 2018 at 9:39 AM, Carsten Bock <carsten at ng-voice.com>
> wrote:
>
>> Hi,
>>
>> likely, the best solution is here to use RTPEngine, so the IP/Port
>> stays identical for each request... i've tested it with various VoLTE
>> phones and various PCRF's.
>>
>> Thanks,
>> Carsten
>> --
>>
>> Carsten Bock
>> CEO (Geschäftsführer)
>>
>> ng-voice GmbH
>> Millerntorplatz 1
>> 20359 Hamburg / Germany
>>
>> http://www.ng-voice.com
>> mailto:carsten at ng-voice.com
>>
>> Office +49 40 5247593-40
>> Fax +49 40 5247593-99
>>
>> Sitz der Gesellschaft: Hamburg
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>> Geschäftsführer: Carsten Bock
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>>
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>> http://www.ng-voice.com/imprint/
>>
>>
>> 2018-04-26 15:59 GMT+02:00 Alfonso Pinto <alfonso.pinto at gmail.com>:
>> > Hi Alex,
>> >
>> > Thanks for your answer. I was thinking more or less the same, but it
>> seems I
>> > oversimplified the example and was missing an important point.
>> > This is IMS, so in the middle there are a lot more in the middle. It
>> seems
>> > that this behaviour is normal when precondition is set and the only way
>> to
>> > avoid the network to release the call on A side is to send the update.
>> > I've seen that in Kamailio 5 a new function was included in TM:
>> > https://www.kamailio.org/docs/modules/5.1.x/modules/tm.html#
>> tm.f.t_uac_send
>> > In the code it looks like it's trying to use the current dialog, but
>> that
>> > gives me doubts about CSEQ handling on the other side.
>> >
>> > Anyway, I will try unless someone is faster replying saying it doesn't
>> work
>> > :)
>> >
>> > Thanks,
>> > Alfonso.
>> >
>> > On Thu, Apr 26, 2018 at 2:37 PM, Alex Balashov <
>> abalashov at evaristesys.com>
>> > wrote:
>> >>
>> >> I would instead redirect my focus to why A is dropping the call in this
>> >> situation. It shouldn't be doing that.
>> >>
>> >> Per the standards, the first SDP answer must be the final SDP answer
>> >> (absent an update or reinvite) *of that endpoint*. There's no rule
>> saying
>> >> that must be true of the dialog as a whole.
>> >>
>> >> -- Alex
>> >>
>> >> --
>> >> Sent via mobile, please forgive typos and brevity.
>> >>
>> >> _______________________________________________
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>> >
>> >
>> >
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