Source note · Troubleshooting calls that drop on hold or transfer
Teams Direct Routing chooses its transfer method from the capabilities the SBC advertises: if the SBC's Allow header includes REFER, the SIP proxy sends REFER to the SBC and acts as Transferor; otherwise the proxy handles the transfer itself as Referee.
Checked 2026-09-30
If the SBC indicates that it supports the method “Refer”, the SIP proxy uses Option 2 for call transfers.
- Vendor
- Microsoft
- Product
- Teams Phone Direct Routing
- Subsystem
- call-transfer
- Deployment
- multi-tenant
- Region
- not restricted
- Release range
- current as of 2026-09-30
- Checked
- 2026-09-30
Sources
- Teams Phone System Direct Routing: SIP protocol — Microsoft · tier 2 current vendor documentation · Call transfer
Cite this note
APA
WarmTransfer. (2026, September 30). Troubleshooting calls that drop on hold or transfer: source note sip-reinvite-call-drops-dr-transfer-method-by-allow. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-reinvite-call-drops-dr-transfer-method-by-allow
BibTeX
@misc{warmtransfer-claim-sip-reinvite-call-drops-dr-transfer-method-by-allow,
title = {Troubleshooting calls that drop on hold or transfer: source note sip-reinvite-call-drops-dr-transfer-method-by-allow},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-reinvite-call-drops-dr-transfer-method-by-allow},
note = {Source note sip-reinvite-call-drops-dr-transfer-method-by-allow, checked 2026-09-30}
}