Source note · SIP 503 and trunk out-of-service failures
An SBC that has not sent OPTIONS on schedule is demoted rather than removed: it is not tried first, but it is tried again before the call fails if the other SBCs in the route cannot deliver it.
Checked 2026-09-25
- Vendor
- Microsoft
- Product
- Teams Phone Direct Routing
- Subsystem
- SBC health monitoring
- Deployment
- multi-tenant
- Region
- not restricted
- Release range
- current as of 2026-09-25
- Checked
- 2026-09-25
Sources
- Monitor Direct Routing — Microsoft · tier 2 current vendor documentation · Section 'Monitoring availability of Session Border Controllers using Session Initiation Protocol (SIP) options messages', demotion paragraphs
Cite this note
APA
WarmTransfer. (2026, September 25). SIP 503 and trunk out-of-service failures: source note sip-503-trunk-failures-dr-demotion. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-503-trunk-failures-dr-demotion
BibTeX
@misc{warmtransfer-claim-sip-503-trunk-failures-dr-demotion,
title = {SIP 503 and trunk out-of-service failures: source note sip-503-trunk-failures-dr-demotion},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-503-trunk-failures-dr-demotion},
note = {Source note sip-503-trunk-failures-dr-demotion, checked 2026-09-25}
}