Locate the response family
- 1xx ProvisionalRequest is progressing
- 2xx SuccessRequest succeeded
- 3xx RedirectionAnother destination
- 4xx Request failureInterpret this request487 belongs here
- 5xx Server failureServer could not fulfil
- 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
The pending request was terminated, commonly after cancellation. In an INVITE flow this can be expected when the caller abandons the call before answer.
Read it in context
A caller hanging up while ringing or an intermediary cancelling another fork can lead to 487. The response often describes the consequence of a cancellation rather than the original reason a person did not answer.
Administrator checks
Find the preceding CANCEL or related termination event and identify its source. Correlate the INVITE transaction and the separate response to CANCEL. If cancellations are unexpected, inspect the upstream timeout or user action that triggered them.
Next action and common mistake
Do not count every 487 as a carrier outage. Separate caller abandonment from system-generated cancellation and inspect answer/cancel races. After a repair, verify normal unanswered, answered and abandoned call behavior rather than suppressing the response.
Sources & applicability
Primary references for the technical details above. Operational examples and planning checklists are VoIP.info editorial guidance.