SIP 181 Call Is Being Forwarded vs 421 Extension Required
SIP 181 (Call Is Being Forwarded) is a 1xx Provisional response, while 421 (Extension Required) is a 4xx Client Failure response. 181 indicates that a proxy server may send this to indicate that the call is being forwarded to a different set of destinations. In contrast, 421 means that the UAS needs a particular extension to process the request but the extension is not listed in the Supported header.
설명
A proxy server may send this to indicate that the call is being forwarded to a different set of destinations.
이 코드를 보게 되는 경우
When the callee has call forwarding enabled and the request is being redirected to another number or device.
해결 방법
No action needed. The call is being redirected. If forwarding is unintended, the callee should update their forwarding settings.
설명
The UAS needs a particular extension to process the request but the extension is not listed in the Supported header.
이 코드를 보게 되는 경우
When the server requires a specific SIP extension that the client did not indicate support for.
해결 방법
Add the required extension to the Supported header and ensure your UA implements it. Check the response for which extension is needed.
주요 차이점
181 is a 1xx Provisional response, while 421 is a 4xx Client Failure response.
SIP 181: A proxy server may send this to indicate that the call is being forwarded to a different set of destinations.
SIP 421: The UAS needs a particular extension to process the request but the extension is not listed in the Supported header.
You encounter 181 when when the callee has call forwarding enabled and the request is being redirected to another number or device.
You encounter 421 when when the server requires a specific SIP extension that the client did not indicate support for.
언제 어떤 것을 사용할지
For 181 (Call Is Being Forwarded): No action needed. The call is being redirected. If forwarding is unintended, the callee should update their forwarding settings. For 421 (Extension Required): Add the required extension to the Supported header and ensure your UA implements it. Check the response for which extension is needed.