Hi colleagues, 

It’s worth mentioning that PRACK (and 200 OK for PRACK) often participates in 
SDP offer/answer negotiation (RFC 3262, RFC 6337). I’m wondering how this can 
be implemented solely on the SIP proxy side?
—
Alexey Vasilyev

> 14 нояб. 2025 г., в 10:39, Johan De Clercq <[email protected]> написал(а):
> 
> pfff, indeed. 
> you save a tiny little bit of networking traffic, that's the only thing that 
> I see. 
> 
> okay, 
> so the module should contain 
> - 200 OK'ing prack. 
> - (be able to send prack (?, if there is a use case)). 
> - handle update (via rtpprxoy and rtpengine). 
> 
> 
> Op vr 14 nov 2025 om 10:33 schreef Giovanni Maruzzelli <[email protected] 
> <mailto:[email protected]>>:
>> > It really is a mess, to me it seems that IMS guys are scared of rtp
>> +1 it is an endpoint thing, trunk providers are wrong to ask for it (what do 
>> they get from it?)
>> 
>> when you (trunk provider) know that the phone is actually ringing, what do 
>> you gain? It has meaning when you control the whole chain, end-to-end 
>> (carriers, IMS) not at all for 
>> deskphone->itsp->trunk->whatever->carrier->endphone
>> 
>> But I know they (trunk providers) start to *REQUIRE* PRACK
>> 
>> So, probably a module, or an extension of an existing module, can be 
>> warranted and welcome
>> 
>> Possibly on 3.6.X (that's the last LTS of the 3.0.0 series)
>> 
>> Let's open a thread on what functionalities can be useful in it?
>> 
>> -giovanni
>> 
>> 
>> On Fri, Nov 14, 2025 at 10:21 AM Johan De Clercq <[email protected] 
>> <mailto:[email protected]>> wrote:
>>> +1.  I totally agree with you. 
>>> It really is a mess, to me it seems that IMS guys are scared of rtp. 
>>> 
>>> Op vr 14 nov 2025 om 10:03 schreef Walter Schober <[email protected] 
>>> <mailto:[email protected]>>:
>>>> Hi!
>>>> 
>>>>  
>>>> 
>>>> I also want to point out that its not done with PRACK handling alone. 
>>>> Followup (multiple) UPDATE with codec changes must be handled, too. 
>>>> Sometimes that lead into AMR(WB)/PCMA/G722/OPUS transcoding in early 
>>>> state. Including all the DTMF PT issues.
>>>> 
>>>> It is definitely a endpoint / softswitch feature.
>>>> 
>>>>  
>>>> 
>>>> I know those ignorant IMS guys pushing out their internal mess to plain 
>>>> RFC3261 interconnects and forcing tasks previously done by an MSC to the 
>>>> rest of the world.
>>>> 
>>>>  
>>>> 
>>>> Br
>>>> 
>>>> Walter  
>>>> 
>>>>  
>>>> 
>>>> Von: Users <[email protected] 
>>>> <mailto:[email protected]>> Im Auftrag von Johan De Clercq
>>>> Gesendet: Donnerstag, 13. November 2025 16:29
>>>> An: [email protected] <mailto:[email protected]>; OpenSIPS users 
>>>> mailling list <[email protected] <mailto:[email protected]>>
>>>> Betreff: Re: [OpenSIPS-Users] 100rel / PRACK Interworking
>>>> 
>>>>  
>>>> 
>>>> Giovanni on a side note, what to do with update ? do you handle it locally 
>>>> or do you forward it to your endpoint ? 
>>>> 
>>>>  
>>>> 
>>>> BR, Johan. 
>>>> 
>>>>  
>>>> 
>>>> Op do 13 nov 2025 om 15:54 schreef Giovanni Maruzzelli <[email protected] 
>>>> <mailto:[email protected]>>:
>>>> 
>>>> Antonio, you may want to update this feature request from Johan: 
>>>> https://github.com/OpenSIPS/opensips/issues/2076
>>>> 
>>>>  
>>>> 
>>>> On Thu, Nov 13, 2025 at 3:48 PM Antonios Psaras <[email protected] 
>>>> <mailto:[email protected]>> wrote:
>>>> 
>>>> Hello Giovanni
>>>> 
>>>>  
>>>> 
>>>> I totally agree with you. PRACK is an endpoint feature. But as you know, 
>>>> working with IMS, and having all kind or end point implementations of sip 
>>>> stack you need to do the dirty job in the middle for interoperability 
>>>> reasons. Commercial SBC have that feature called 100rel Interworking which 
>>>> can be enabled per Trunk. Hence, if a carrier requires 100rel/PRACK 
>>>> enforcement and the end point does not supporting it, the function is 
>>>> engaged and handles the PRACK locally.
>>>> 
>>>>  
>>>> 
>>>> I will check Bogdan suggestion but in the first read looks like a tmp work 
>>>> around which I am not sure if that can be scaled to few hundreds of CPS 
>>>> that we work with.
>>>> 
>>>>  
>>>> 
>>>> As this is a feature that will be needed for VoLTE/5G/IMS networks my 
>>>> suggestion is to create a module for that.
>>>> 
>>>>  
>>>> 
>>>> Regards
>>>> 
>>>>  
>>>> 
>>>>  
>>>> 
>>>> From: Giovanni Maruzzelli <[email protected] <mailto:[email protected]>> 
>>>> Sent: Πέμπτη, 13 Νοεμβρίου 2025 16:37
>>>> To: [email protected] <mailto:[email protected]>; OpenSIPS users 
>>>> mailling list <[email protected] <mailto:[email protected]>>
>>>> Subject: Re: [OpenSIPS-Users] 100rel / PRACK Interworking
>>>> 
>>>>  
>>>> 
>>>>  
>>>>  
>>>> El 26/02/2024 a las 7:43 a. m., Bogdan-Andrei Iancu escribió:
>>>> > yes, you can use the b2b_logic (together with b2b_entities) for that, 
>>>> > but it may be a too heavy tool for the purpose. Maybe you can try to 
>>>> > generate the PRACK from OpenSIPS level by using the t_uac_dlg MI 
>>>> > function [1] via the mi_script module [2] - basically to trigger that 
>>>> > MI cmd from the onreply_route, when receiving the 180 reply.
>>>> > 
>>>> > [1] https://opensips.org/html/docs/modules/3.4.x/tm.html#mi_t_uac_dlg
>>>> > [2] https://opensips.org/html/docs/modules/3.4.x/mi_script.html#afunc_mi 
>>>>  
>>>>  
>>>>  
>>>> 
>>>> On Thu, Nov 13, 2025 at 3:34 PM Giovanni Maruzzelli <[email protected] 
>>>> <mailto:[email protected]>> wrote:
>>>> 
>>>>  
>>>> 
>>>>  
>>>> 
>>>> eg: https://lists.opensips.org/pipermail/users/2024-March/047880.html
>>>> 
>>>>  
>>>> 
>>>>  
>>>> 
>>>>  
>>>> 
>>>> On Thu, Nov 13, 2025 at 3:27 PM Giovanni Maruzzelli <[email protected] 
>>>> <mailto:[email protected]>> wrote:
>>>> 
>>>> Hello Antonio,
>>>> 
>>>>  
>>>> 
>>>> PRACK is actually an endpoint feature, at the proxy level you can only 
>>>> fake it...
>>>> 
>>>>  
>>>> 
>>>> -giovanni
>>>> 
>>>>  
>>>> 
>>>> On Thu, Nov 13, 2025 at 3:14 PM Antonios Psaras <[email protected] 
>>>> <mailto:[email protected]>> wrote:
>>>> 
>>>> Dear Team
>>>> 
>>>>  
>>>> 
>>>> As many carriers requires 100rel for interoperability reason with IMS, the 
>>>> need for 100rel interworking is mandatory. Is there any solution available 
>>>> to implement that on OpenSIPs Proxy level?
>>>> 
>>>>  
>>>> 
>>>> Regards
>>>> 
>>>>  
>>>> 
>>>> Antonis Psaras
>>>> 
>>>>  
>>>> 
>>>>  
>>>> 
>>>> _______________________________________________
>>>> Users mailing list
>>>> [email protected] <mailto:[email protected]>
>>>> http://lists.opensips.org/cgi-bin/mailman/listinfo/users
>>>> 
>>>> 
>>>> 
>>>>  
>>>> 
>>>> --
>>>> 
>>>> Sincerely,
>>>> 
>>>> Giovanni Maruzzelli
>>>> OpenTelecom.IT
>>>> cell: +39 347 266 56 18
>>>> 
>>>> 
>>>> 
>>>>  
>>>> 
>>>> --
>>>> 
>>>> Sincerely,
>>>> 
>>>> Giovanni Maruzzelli
>>>> OpenTelecom.IT
>>>> cell: +39 347 266 56 18
>>>> 
>>>> 
>>>> 
>>>>  
>>>> 
>>>> --
>>>> 
>>>> Sincerely,
>>>> 
>>>> Giovanni Maruzzelli
>>>> OpenTelecom.IT
>>>> cell: +39 347 266 56 18
>>>> 
>>>> 
>>>> 
>>>>  
>>>> 
>>>> --
>>>> 
>>>> Sincerely,
>>>> 
>>>> Giovanni Maruzzelli
>>>> OpenTelecom.IT
>>>> cell: +39 347 266 56 18
>>>> 
>>>> _______________________________________________
>>>> Users mailing list
>>>> [email protected] <mailto:[email protected]>
>>>> http://lists.opensips.org/cgi-bin/mailman/listinfo/users
>>>> 
>>>> _______________________________________________
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>>> _______________________________________________
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>> 
>> 
>> 
>> --
>> Sincerely,
>> 
>> Giovanni Maruzzelli
>> OpenTelecom.IT
>> cell: +39 347 266 56 18
>> 
>> _______________________________________________
>> Users mailing list
>> [email protected] <mailto:[email protected]>
>> http://lists.opensips.org/cgi-bin/mailman/listinfo/users
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