Apparently for Deutsche Telekom - Company Flex / 1TR119 you need to send only one specific codec in your 183 SDP answer. But there is no way to state that in the trunk. You need to add something like this in
This works then as expected. The reason why we did that is, we had incoming calls from mobile phones from the vodafone network (@ims.mnc002.mcc262.3gppnetwork.org or @ims.vodafone.de) which terminated after n-seconds. And provider Deutsche Telekom says, 1TR119 must have only one codec in the 183 answer (and we sent g722/alaw). Now we have our list of allowed codecs but in that answer now there is only one of those.
So, is there a way to have that setting in the GUI somewhere in the future?
Oh this is a new one for me. To be fair there are some more settings missing in the GUI to make a SIP-Trunk work with Deutsche Telekom.
For example there is no predefined context to use the P-Called-Party-ID header for DID routing. Also there is missing an option to send the P-Preferred-Identity header on outgoing calls. There is an option to send the P-Asserted-Identity header which is also accepted by Deutsche Telekom, but you cannot predefine a number here and FreePBX always sets the number from the FROM header as the value. This will break external call forwarding when you use CLIP no screening.
We are still using the older product DeutschlandLAND SIP-Trunk from Deutsche Telekom but I think Company Flex requires the same settings.
I’m pretty sure PAI is the caller ID. I think FreePBX allows you to force the From header to something else. Asterisk set PAI to caller ID, so FreePBX would have to explicitly add the header, and I don’t think it dos, to set it to anything else.
Okay maybe my description was a little bit misleading. What I meant is that if you enable PAI in the trunk settings, FreePBX will always set the original caller id as the PAI. So when an external user A calls an extension B and the extension forwards the call to another external destination C it will set the caller id of A in the PAI. But Deutsche Telekom does not allow that. The PAI have to be valid number from the trunk. In this case the PAI should be the number of B or the base number of the trunk.