[SR-Users] How to handle BYE in case of serial fork

Björn Klasen bklasen at tng.de
Fri Sep 11 16:24:50 CEST 2020

Hi Henning,

i think I've got a solution for this. I just make a check 
is_known_dialog. If not i reply with 481

I'm just testing, but it seem to work. The carrier is not sending 
retransmission of the BYE and the call seems to be stable.

By the way, the carrier is Telekom so discussions about standard is 
worthless here ;)


Am 11.09.20 um 16:00 schrieb Henning Westerholt:
> Hello Björn,
> 1) about the signalisation
> The different 180 responses establishing different early dialogs, each with its own to-tag, as required from the standard. The 200 OK for the winning branch will then initialize the dialog. The BYE to this dialog should include the winning branch to-tag (in your case the TT2). Your carrier sends also a BYE to the early dialog, which is not recommend from the standard, but it is not forbidden.
> 2) about Kamailio routing
> I am not sure what you mean with "Kamailio cannot find the to-tag in memory". The method has_totag() is just checking for the existence of an to-tag in the message, without any memory storage involved.
> The warning about the tight dialog matching failed is just a warning, if you do not use the dialog module for routing decision it should not cause these problems.
> Your Kamailio should forward the BYE according to the Route header (if there is one) or the request-URI. In your example message below, this would be to the sems server.
> If you want to implement some other logic, you can use e.g. the htable module to store information about call branches for some time and then expire it later on.
> Cheers,
> Henning
Björn Klasen, Specialist
TNG Stadtnetz GmbH, Network Management (VoIP)
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