Forum Discussion
MS Teams Direct Routing - Internal call transfer failure
Hi Sim,
We've got exactly the same behaviour when trying to transfer calls that came from PSTN network and got answered by one of our Teams users and when they try to transfer to another Teams user. REFER-TO doesn't contain any LineURI or telephone number to complete the transfer. Did you have any luck fixing this issue? Also, I'm not sure if this was working before or not. But you seem to be correct in regards to Teams treating internal transfer as external one and sending SIP REFER back to SBC without providing any additional details in regards where the call should be actually connected or transferred to. When transferring to external number this works perfectly fine, REFER-TO contains an external number and can be processed by our SBC. BTW, can you tell what SBC are you using? Is it AudioCodes or Ribbon one? Or something not currently certified by Microsoft? Thanks!
Lt_Flash We're using AudioCodes, and config wise its fine. It handles REFERs just fine. The issue here is that MS Teams should never had sent this REFER out the SBC, it should have handled it within the Teams environment as its a transfer from one Teams user to another. This only thing I suspect config wise is voice route regex I'm using, as its pretty much a catch all e.g. ".*"
I've now made it more strict to capture digit patterns rather than all chars to see if the issue persists.
It makes no sense as I can call users internally, it only happens when PSTN call comes in from the direct Routing SBC, so Teams appears to be applying a different call routing logic when applying the transfer.
Out of curiosity can you let me know what your voice route pattern looks like? Was it a catch all like mine or is it more strict?
Thanks,
Sim
Yes, I'm using the same voice pattern, ".*" to send all digits without any normalization to our SIP trunk. You're right, maybe the issue is because of that, I will update voice rules tomorrow to make it strictly country-based, like '^+44.*' to see if that helps! Good point, mate!
Also, yes, SIP REFER shouldn't be coming back to PBX when we're doing an internal transfer from one Teams User to another one, but it does for some reason, that's the problem.
I'll let you know here how it goes and thanks for your reply!Hi Sims,
I've removed the ".*" rule from my installation and created all specific rules for DIDs and still no luck, I can see SIP REFER coming back to PBX when I'm trying to transfer call that came from PSTN to Teams user. No luck here, unfortunately. Did you have any luck with this? Thanks.
Lt_Flash I had no luck with changing the voice route, so ended up raising it with MS support.
Apparently if you disable REFER as an allowed method within your SBC's signalling messages, then MS Teams does not use REFER for transfers and just re-INVITEs to the SBC. That way the internal transfers work perfectly fine.