Source note · SIP 503 and trunk out-of-service failures
Direct Routing requires a successful OPTIONS exchange (200 OK) between the SBC and the Microsoft SIP proxy before calls can be set up.
Checked 2026-09-25
- Vendor
- Microsoft
- Product
- Teams Phone Direct Routing
- Subsystem
- OPTIONS
- 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 · Section 'Processing the incoming request: finding the tenant and user'
Cite this note
APA
WarmTransfer. (2026, September 25). SIP 503 and trunk out-of-service failures: source note sip-503-trunk-failures-dr-options-200-needed. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-503-trunk-failures-dr-options-200-needed
BibTeX
@misc{warmtransfer-claim-sip-503-trunk-failures-dr-options-200-needed,
title = {SIP 503 and trunk out-of-service failures: source note sip-503-trunk-failures-dr-options-200-needed},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-503-trunk-failures-dr-options-200-needed},
note = {Source note sip-503-trunk-failures-dr-options-200-needed, checked 2026-09-25}
}