[SR-Users] Manage multiple RTP streams with different TO-tags (forking)

[Patrick Wakano]

I did have a very similar problem and it got solved by using the
via-branch=auto in the rtpengine offer....
Check the comments here:
https://github.com/sipwise/rtpengine/commit/23977237c0753c9877b082d71d45348387ad1606

On Fri, 27 Aug 2021 at 21:40, Julien Klingenmeyer <
julien.klingenmeyer at ovhcloud.com> wrote:

> Hi,
>
>
>
> I faced a quite same situation recently and I have asked on RTPEngine
> Github: https://github.com/sipwise/rtpengine/issues/1330
>
> Your scenario is a bit different but with the workaround described in the
> issue (overriding to-tag flag in rtpengine request), maybe you can fix your
> issue.
>
>
>
> Just also be careful when either Alice or Bob sends ReInvites within the
> call, to-tag (or from-tag depending on who sent the request) will need to
> be overridden too.
>
>
>
> Julien
>
>
>
> *De : *sr-users <sr-users-bounces at lists.kamailio.org> au nom de Arsen
> Semenov <arsperger at gmail.com>
> *Répondre à : *"Kamailio (SER) - Users Mailing List" <
> sr-users at lists.kamailio.org>
> *Date : *vendredi 27 août 2021 à 07:28
> *À : *"Kamailio (SER) - Users Mailing List" <sr-users at lists.kamailio.org>
> *Objet : *Re: [SR-Users] Manage multiple RTP streams with different
> TO-tags (forking)
>
>
>
> it's legal to get responses with different to-tags, since the request is
> forked. this is what's happening in this scenario.
> I think this is an issue of UAC/rtpengin how it is reacting to the second
> SDP in 183
>
>
>
> are the SDPs in 183 responses carried reliably?
>
>
>
> On Fri, Aug 27, 2021 at 2:51 PM Yuriy Gorlichenko <ovoshlook at gmail.com>
> wrote:
>
> Hello.
>
> The first thing: to tag can't be changed due session once it passed.
>
>
>
> If provider uses forking mechanism the it has to be hidden from your
> system.
>
>
>
> Regarding SDP according
>
> https://datatracker.ietf.org/doc/html/rfc3261#section-13.2.1
>
> They can't change SDP answer description on the fly. Only first SDP answer
> used as proper, all othe answers will be ignored.
>
>
>
> On Fri, 27 Aug 2021, 11:27 B. Tietz, <benjamin.tietz at berlin.de> wrote:
>
> Hello,
>
>
>
> following situation.
>
> I have a Kamailio (5.4) using rtpengine to loadbalance calls.
>
>
>
> If a call from Alice comes in, Kamailio decides to send the call to
> Carrier B from Bob.
>
> Bobs Phone is ringing and the carrier B send a 183 Session Progress with
> SDP and To-tag=abcd. The SDP has G722 as codec and port 1234.
>
> A few moments later carrier B send a second 183 Session Progress with SDP
> and TO-tag=fghi. The SDP has G711 as codec and port 5678. This is done, to
> play some funky music as ringtone -.-
>
> If Bob answers the call, carrier B sends a 200 OK WITHOUT SDP and
> TO-tag=abcd. So this should instruct our Kamailio to switch to the first
> G722 and port 1234.
>
>
>
> But sadly, this is just not working as expected.
>
>
>
> We tried to set the flags media-handover and port-latching for the
> rtpengine options and additionally set a to-tag when using rtpenging_manage.
>
> But this doesn't solve the codec change, so we have only audio when Bob
> answers the call, but no ringtone-music. If we allow G711 only in the
> outgoing INVITE to Bob, we have also tha ringtone-muisic, because there is
> no codec-change.
>
>
>
> Carrier B tells us, they are using a fork-mechanism.
>
>
>
> Is there something we can do, to support the codec change in 183? Or
> enforce carrier B to send SDP in 200 OK? Or anything else?
>
>
>
> Carrier B can not change anything in the ringtone-music-backend. They are
> stuck on G711.
>
>
>
> Thanks!
>
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>
>
>
> --
>
> Arsen Semenov
>
>
> __________________________________________________________
> Kamailio - Users Mailing List - Non Commercial Discussions
>   * sr-users at lists.kamailio.org
> Important: keep the mailing list in the recipients, do not reply only to
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