SIP 199 Early Dialog Terminated vs 416 Unsupported URI Scheme
SIP 199 (Early Dialog Terminated) is a 1xx Provisional response, while 416 (Unsupported URI Scheme) 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, 416 means that the server cannot process the request because the URI scheme in the Request-URI is unknown to the server.
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 server cannot process the request because the URI scheme in the Request-URI is unknown to the server.
When You See It
When using a URI scheme (e.g., tel:, im:, pres:) that the receiving server does not support.
How to Fix
Use a supported URI scheme. Most SIP servers support sip: and sips: schemes. Check server capabilities with OPTIONS.
Key Differences
199 is a 1xx Provisional response, while 416 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 416: The server cannot process the request because the URI scheme in the Request-URI is unknown to the server.
You encounter 199 when in forked call scenarios when one of the forked branches is cancelled because another branch was answered.
You encounter 416 when when using a URI scheme (e.g., tel:, im:, pres:) that the receiving server does not support.
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 416 (Unsupported URI Scheme): Use a supported URI scheme. Most SIP servers support sip: and sips: schemes. Check server capabilities with OPTIONS.