Re: RTPEngine and branch_route

Ihor,

Thanks for the reply,

I actually tried using via-branch=extra to resolve my issue, and I almost
had it fixed but couldn't figure out what the ;branch= would contain on the
outbound branch. If I hadn't gotten a solution from Richard, I was going to
write the via-branch=$T_Branch_idx  on the request and the last character
of the branch= of the top via header as the via-branch= on the reply.

However, I like Richard's solution better, it seems safer.

I do like the idea of using the branch id to track client type, though I
was using parameters on the Route headers.

Thanks.

David

On Thu, Aug 7, 2025 at 11:10 AM Ihor Olkhovskyi via sr-users <
[email protected]> wrote:

> David,
>
> I'm having exact the same setup with different type of clients behind
> Kamailio.
>
> I'm using approach like
>
> modparam("rtpengine", "extra_id_pv", "$avp(via_branch_extra_id)")
>
> ...
> $avp(via_branch_extra_id) = "srtp"; # For one type of clients
> ...
> $avp(via_branch_extra_id) = "dtls"; # For other type of clients
> ...
> rtpengine_manage("... via-branch=extra")
> ....
> So, basically relying not on Via branch, but client type.
>
> Maybe this will give a hint
>
> Le jeu. 7 août 2025 à 03:07, David Tek via sr-users <
> [email protected]> a écrit :
>
>> Hello,
>>
>> Using Kamailio 6.0.2.
>>
>> I'm running a registrar that can fork incoming calls to two or more
>> registered users. Some users are WebRTC and others are not, so RTPEngine
>> needs to handle them differently.
>>
>> In the branch route, I call:
>> rtpengine_manage("via-branch=auto replace-origin");
>>
>> However, the via-branch passed to RTPEngine doesn't match the branch ID
>> of the actual INVITEs sent out.
>>
>> When one branch answers, the others get a CANCEL, but the CANCEL/200 OK
>> sent to RTPEngine includes a different via-branch than the one used for
>> the original INVITE. This causes media handling issues.
>>
>> I saw that the docs suggest using $T_branch(name) or AVPs to set the
>> correct branch name, but $T_branch(name) seems deprecated or removed.
>>
>> In previous setups, branching was done on a separate instance, so
>> identifying the right branch was easier. Now that it's local, I’m unsure
>> how to arm rtpengine_manage() with the correct via-branch.
>>
>> *TL;DR:*
>> When doing local forking, how can I set the correct via-branch value for
>> each leg in rtpengine_manage()?
>>
>> Thanks,
>> David
>>
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>
>
> --
> Best regards,
> Ihor (Igor)
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