[OpenSIPS-Users] PRACK interworking requirements

[Vlad Paiu]

note that we currently have 
https://opensips.org/html/docs/modules/3.6.x/dialog.html#func_dlg_send_sequential 
, it can be used to generate a PRACK ( you'll have to manually add the 
Rseq header), but it's not working properly if the upstream has multiple 
TO-TAGS that are ringing ( it will always generate to the newest learnt 
to-tag, and there's also some quirks with CSEQ mapping ), so perhaps the 
'manual' approach would be getting dlg_send_sequential to work properly 
for generating early requests ( with PRACK being a rather specific 
use-case due to it's cseq/rseq stuff )

On 11/25/25 13:14, Giovanni Maruzzelli wrote:
>
> On Tue, Nov 25, 2025, 11:57 Bogdan-Andrei Iancu <bogdan at opensips.org> 
> wrote:
>
>
>     The result here should be a dlg dedicated function to generate a
>     PRACK from the onreply_route, like "dlg_answer_with_prack()" kind
>     of function? or should we look into a more automatic approach,
>     like flagging the dialog at creation to automatically generate the
>     PRACK upon replies flagged with so?
>
>
> personally I'm a control freak and would like better an explicit 
> function, maybe even with parameters to modify things if needed :))
>
> -giovanni
>
>
>
>
>
>
>     Regards,
>
>     Bogdan-Andrei Iancu
>
>     OpenSIPS Founder and Developer
>        https://www.opensips-solutions.com
>        https://www.siphub.com
>
>     On 25.11.2025 11:46, Giovanni Maruzzelli wrote:
>>     hello OpenSIPSers,
>>
>>     in previous mails has been noticed that various ITSPs are
>>     starting to require PRACK support.
>>
>>     We know that PRACK belongs to endpoints, specifically phones and
>>     B2BUAs.
>>
>>     But...
>>
>>     There can be a use case where OpenSIPS will work as SBC (not
>>     necessarily using the b2b module)
>>
>>     So, we can have a case where we would like to support that the
>>     dialogue module insert the 100rel in the Supported: INVITE's
>>     header, and manage to send a PRACK method to acknowledge
>>     provisional responses
>>
>>     If and when 100rel/PRACK are "generated" by OpenSIPS, they will
>>     be filtered out (not propagated) to/from the endpoints, even if
>>     the endpoint would like to support it
>>
>>     Reference RFC: https://www.ietf.org/rfc/rfc3262.txt
>>
>>     I believe this will be enough to make ITSPs happy.
>>
>>     Further developments can be moved to future.
>>
>>     Would be very very nice to have this feature backported to
>>     OpenSIPS 3.6, being it the last of the 3.X series, and an LTS
>>
>>     Please let's gather here your thoughts , requests, corrections
>>     and observations on this issue.
>>
>>     Have a nice Monday you all!
>>
>>     -giovanni
>>
>>     -- 
>>     Sincerely,
>>
>>     Giovanni Maruzzelli
>>     OpenTelecom.IT
>>     cell: +39 347 266 56 18
>>
>>
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>
>
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