Locate the response family
- 1xx ProvisionalRequest is progressing
- 2xx SuccessRequest succeeded
- 3xx RedirectionAnother destination
- 4xx Request failureInterpret this request
- 5xx Server failureServer could not fulfil502 belongs here
- 6xx Global failureFailure across destinations
Read the status with its request method and call leg. For example, 200 after REGISTER confirms a binding; it does not prove an INVITE succeeded.
What this response means
A gateway or proxy received an invalid response from a downstream server while attempting to fulfill the request. The problematic interaction can be beyond your endpoint.
Read it in context
Interworking or downstream response handling may be involved. A local handset can receive 502 even when it sent a valid request and the failure occurred on a carrier-to-carrier leg.
Administrator checks
Identify the component producing the response and whether a downstream exchange is visible. Compare another destination or route under authorized test conditions. Keep timestamps and carrier identifiers so the service operating that boundary can investigate.
Next action and common mistake
Do not equate SIP 502 with a specific web-server failure or change phone credentials without evidence. Validate the repaired destination and any configured alternate route, checking caller identity and media independently.
Sources & applicability
Primary references for the technical details above. Operational examples and planning checklists are VoIP.info editorial guidance.