SIP 503 and Microsoft response codes - Microsoft Teams

Publisher

Microsoft

URL

https://learn.microsoft.com/en-us/troubleshoot/microsoftteams/phone-system/direct-routing/microsoft-sip-response-codes-503

Published

2024-11-22

Updated

unknown

Accessed

2026-09-25

HTTP status

200

License

Microsoft Learn terms of use; no-redistribution; short excerpts and locators only

Source notes citing this source

• Direct Routing Microsoft response code 10320 with SIP 503 means a bot (for example built-in call recording) was unreachable or did not answer before the timeout. in context
• Microsoft's SIP 503 response-code guidance applies to Direct Routing PSTN calls and not to Calling Plan or Operator Connect deployments. in context
• Direct Routing Microsoft response code 540998 with SIP 503 (Service state Inactive/DrainingTransactions) is expected while Microsoft SIP endpoints are down for maintenance and normally needs no action. in context
• Direct Routing Microsoft response code 560503 with SIP 503 means the 503 came from the SBC (maintenance or temporary overload); Microsoft says to check SBC logs, confirm the SBC is licensed for the concurrent sessions, and see whether the failures are tied to one destination country, region or corridor. in context
• If 540998/503 occurs often, Microsoft says to check that the SBC re-resolves the Direct Routing FQDNs frequently, ideally every 15 minutes or more often. in context
• Microsoft response code 540998 with SIP 503 ('Service state: Inactive/DrainingTransactions') is expected while Microsoft SIP endpoints are down for maintenance, and normally needs no action. If it happens often, check that the SBC re-resolves DNS frequently, ideally every 15 minutes or more often. in context
• Microsoft response code 560503 with SIP 503 means the SBC itself returned 503 (maintenance or overload). Microsoft says to check the SBC logs, check that the SBC is licensed for the concurrent session count, and see whether the failures cluster on a particular destination country or calling corridor. in context

Cite this source record

APA

WarmTransfer. (2024, November 22). SIP 503 and Microsoft response codes - Microsoft Teams. WarmTransfer. https://warmtransfer.net/knowledge/sources/ms-learn-troubleshoot-dr-sip-503

BibTeX

@misc{warmtransfer-ms-learn-troubleshoot-dr-sip-503,
  title  = {SIP 503 and Microsoft response codes - Microsoft Teams},
  author = {{WarmTransfer}},
  year   = {2024},
  url    = {https://warmtransfer.net/knowledge/sources/ms-learn-troubleshoot-dr-sip-503},
  note   = {Microsoft, accessed 2026-09-25}
}