Setting up Freeswitch to connect to Microsoft Teams' "Direct Routing" (https://docs.microsoft.com/en-us/microsoftteams/direct-routing-plan). General call setup-teardown is successful, but I'm encountering a problem with call transfers if the transfer target is another Microsoft Teams user. The most immediate obvious difference between the transfer to an external party and the transfer to another Teams user is in the Refer-To header of the Refer message on the transfer event. In the case of transfer to an external party, the Refer-To is (phone number redacted to 555-555-1000):
REFER-TO: <sip:+15555551000@sip.pstnhub.microsoft.com:5061;user=phone;transport=tls>
In the case of transfer to another Teams user, the transfer Refer-To: header looks like this:
REFER-TO: <sip:sip.pstnhub.microsoft.com:5061;transport=tls;x-m=8:orgid:13bc82d9-003a-43b8-aad2-8f2f561a9b8d>
When this occurs, the last line in the Freeswitch log for the call is:
[DEBUG] sofia.c:8544 Process REFER to [(null)@sip.pstnhub.microsoft.com]
There is nothing else in the log until this times out, no indication it has entered any dialplan, etc. Even on timeout, it is just the teams client saying that the call has failed, and unless one end hangs up, or reconnects to the failed transfer, there is no action in freeswitch. I believe this to be a bug, but wanted to get an opinion before opening a formal bug report. Regards, Ben Kaufman AltiGen Communications, Inc. STATEMENT OF CONFIDENTIALITY: The information contained in this electronic message and any attachments to this message are intended for the exclusive use of the addressee(s) and may contain confidential or privileged information. If you are not the intended recipient, or the person responsible for delivering the e-mail to the intended recipient, be advised you have received this message in error and that any use, dissemination, forwarding, printing, or copying is strictly prohibited. Please notify AltiGen Communications immediately at either (888)258-4436 or via email to administrator@altigen.com, and destroy all copies of this message and any attachments.