SIP REFER on externally forwarded call

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smeyer

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Feb 18, 2021
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I am making a new post as I realize I did not fully understand the issue previously (sorry).
Due to STIR/SHAKN and Twilio rules, external transfers like in a call forward scenario, must be initiated in the original inbound SIP dialog. When looking up the proper application, it seems that using "Deflect" SHOULD do that. Now, when I change "call_forward_all" dialplan to deflect instead of transfer, nothing happens. I have attached what my log shows for this action. There is nothing sent in the SIP flow and the call just terminates.
Twilio has a good diagram if someone needs a visual of the proper flow. https://www.twilio.com/docs/sip-trunking/call-transfer
 

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DigitalDaz

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Sep 29, 2016
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Freeswitch is a B2BUA, you shouldn't be needing to use refer at carrier level. The call forwarding is done within the PBX so the forward is just like a regular external call.
 

smeyer

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Feb 18, 2021
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Freeswitch is a B2BUA, you shouldn't be needing to use refer at carrier level. The call forwarding is done within the PBX so the forward is just like a regular external call.
New regulations as well as a few carriers do not let you send an outbound call w/o the CID being verified. So if you want to forward externally and maintain the callee CID, you must use a refer. There are several other companies including bandwidth that have not moved but will be enacting this.
 

Adrian Fretwell

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Aug 13, 2017
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Many carriers will not accept REFER. We always respond to a REFER method with 405 "Method Not Allowed". The B2BUA is the way to go.
 
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