SIP 199 Early Dialog Terminated vs 421 Extension Required
SIP 199 (Early Dialog Terminated) is a 1xx Provisional response, while 421 (Extension Required) is a 4xx Client Failure response. 199 indicates that a UAS can send this to indicate that an early dialog has been terminated. Used when forking results in multiple early dialogs. 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.
Description
A UAS can send this to indicate that an early dialog has been terminated. Used when forking results in multiple early dialogs.
Quand vous le voyez
In forked call scenarios when one of the forked branches is cancelled because another branch was answered.
Comment résoudre
No action needed. This is normal behavior in forked call setups. Ensure your UA handles early dialog termination gracefully.
Description
The UAS needs a particular extension to process the request but the extension is not listed in the Supported header.
Quand vous le voyez
When the server requires a specific SIP extension that the client did not indicate support for.
Comment résoudre
Add the required extension to the Supported header and ensure your UA implements it. Check the response for which extension is needed.
Différences clés
199 is a 1xx Provisional response, while 421 is a 4xx Client Failure response.
SIP 199: A UAS can send this to indicate that an early dialog has been terminated. Used when forking results in multiple early dialogs.
SIP 421: The UAS needs a particular extension to process the request but the extension is not listed in the Supported header.
You encounter 199 when in forked call scenarios when one of the forked branches is cancelled because another branch was answered.
You encounter 421 when when the server requires a specific SIP extension that the client did not indicate support for.
Quand utiliser lequel
For 199 (Early Dialog Terminated): No action needed. This is normal behavior in forked call setups. Ensure your UA handles early dialog termination gracefully. 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.