SIP 199 Early Dialog Terminated vs 406 Not Acceptable
SIP 199 (Early Dialog Terminated) is a 1xx Provisional response, while 406 (Not Acceptable) 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, 406 means that the resource identified by the request is only capable of generating responses with content characteristics not acceptable according to the Accept header.
Description
A UAS can send this to indicate that an early dialog has been terminated. Used when forking results in multiple early dialogs.
When You See It
In forked call scenarios when one of the forked branches is cancelled because another branch was answered.
How to Fix
No action needed. This is normal behavior in forked call setups. Ensure your UA handles early dialog termination gracefully.
Description
The resource identified by the request is only capable of generating responses with content characteristics not acceptable according to the Accept header.
When You See It
When content negotiation fails — the server cannot produce a response matching the Accept header fields in the request.
How to Fix
Review the Accept headers in your request and broaden the acceptable content types.
Key Differences
199 is a 1xx Provisional response, while 406 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 406: The resource identified by the request is only capable of generating responses with content characteristics not acceptable according to the Accept header.
You encounter 199 when in forked call scenarios when one of the forked branches is cancelled because another branch was answered.
You encounter 406 when when content negotiation fails — the server cannot produce a response matching the Accept header fields in the request.
When to Use Which
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 406 (Not Acceptable): Review the Accept headers in your request and broaden the acceptable content types.