Source note · Troubleshooting calls that drop on hold or transfer
Having the SBC handle REFER is Microsoft's preferred transfer method, is mandatory for media bypass certification, and transfer without SBC REFER handling is not supported in media bypass mode.
Checked 2026-09-30
Call Transfer without the SBC being able to handle Refer isn't supported in media bypass mode.
- 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 > SIP proxy send the Refer to the SBC and acts as a Transferor
Cite this note
APA
WarmTransfer. (2026, September 30). Troubleshooting calls that drop on hold or transfer: source note sip-reinvite-call-drops-dr-refer-required-for-bypass. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-reinvite-call-drops-dr-refer-required-for-bypass
BibTeX
@misc{warmtransfer-claim-sip-reinvite-call-drops-dr-refer-required-for-bypass,
title = {Troubleshooting calls that drop on hold or transfer: source note sip-reinvite-call-drops-dr-refer-required-for-bypass},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-reinvite-call-drops-dr-refer-required-for-bypass},
note = {Source note sip-reinvite-call-drops-dr-refer-required-for-bypass, checked 2026-09-30}
}