SIP 202 Accepted vs 421 Extension Required
SIP 202 (Accepted) is a 2xx Success response, while 421 (Extension Required) is a 4xx Client Failure response. 202 indicates that the request has been accepted for processing but the processing has not been completed. Used primarily for REFER requests. 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.
Описание
The request has been accepted for processing but the processing has not been completed. Used primarily for REFER requests.
Когда вы это видите
After sending a REFER request for call transfer. The transfer target acknowledges receipt but hasn't completed the transfer yet.
Как исправить
Wait for a NOTIFY to learn the outcome of the referred action. If no NOTIFY arrives, check subscription state and network connectivity.
Описание
The UAS needs a particular extension to process the request but the extension is not listed in the Supported header.
Когда вы это видите
When the server requires a specific SIP extension that the client did not indicate support for.
Как исправить
Add the required extension to the Supported header and ensure your UA implements it. Check the response for which extension is needed.
Ключевые различия
202 is a 2xx Success response, while 421 is a 4xx Client Failure response.
SIP 202: The request has been accepted for processing but the processing has not been completed. Used primarily for REFER requests.
SIP 421: The UAS needs a particular extension to process the request but the extension is not listed in the Supported header.
You encounter 202 when after sending a REFER request for call transfer. The transfer target acknowledges receipt but hasn't completed the transfer yet.
You encounter 421 when when the server requires a specific SIP extension that the client did not indicate support for.
Когда что использовать
For 202 (Accepted): Wait for a NOTIFY to learn the outcome of the referred action. If no NOTIFY arrives, check subscription state and network connectivity. 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.