Source note · SIP call forwarding and routing loops
Microsoft says that several missed calls for one declined call mean the SBC or PSTN trunk provider's retry mechanism is misconfigured, and the SBC must be reconfigured to stop retrying on a 603 response.
Checked 2026-09-25
- Vendor
- Microsoft
- Product
- Teams Phone Direct Routing
- Subsystem
- SBC retry behaviour
- Deployment
- multi-tenant
- Region
- not restricted
- Release range
- current as of 2026-09-25
- Checked
- 2026-09-25
Sources
- Teams Phone System Direct Routing: SIP protocol — Microsoft · tier 2 current vendor documentation · Handling retries (603 response)
Cite this note
APA
WarmTransfer. (2026, September 25). SIP call forwarding and routing loops: source note sip-forwarding-loops-teams-dr-603-retry. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-forwarding-loops-teams-dr-603-retry
BibTeX
@misc{warmtransfer-claim-sip-forwarding-loops-teams-dr-603-retry,
title = {SIP call forwarding and routing loops: source note sip-forwarding-loops-teams-dr-603-retry},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-forwarding-loops-teams-dr-603-retry},
note = {Source note sip-forwarding-loops-teams-dr-603-retry, checked 2026-09-25}
}