SIP 181 Call Is Being Forwarded vs 416 Unsupported URI Scheme
SIP 181 (Call Is Being Forwarded) is a 1xx Provisional response, while 416 (Unsupported URI Scheme) 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, 416 means that the server cannot process the request because the URI scheme in the Request-URI is unknown to the server.
Descripción
A proxy server may send this to indicate that the call is being forwarded to a different set of destinations.
Cuándo lo verás
When the callee has call forwarding enabled and the request is being redirected to another number or device.
Cómo solucionarlo
No action needed. The call is being redirected. If forwarding is unintended, the callee should update their forwarding settings.
Descripción
The server cannot process the request because the URI scheme in the Request-URI is unknown to the server.
Cuándo lo verás
When using a URI scheme (e.g., tel:, im:, pres:) that the receiving server does not support.
Cómo solucionarlo
Use a supported URI scheme. Most SIP servers support sip: and sips: schemes. Check server capabilities with OPTIONS.
Diferencias clave
181 is a 1xx Provisional response, while 416 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 416: The server cannot process the request because the URI scheme in the Request-URI is unknown to the server.
You encounter 181 when when the callee has call forwarding enabled and the request is being redirected to another number or device.
You encounter 416 when when using a URI scheme (e.g., tel:, im:, pres:) that the receiving server does not support.
Cuándo usar cada uno
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 416 (Unsupported URI Scheme): Use a supported URI scheme. Most SIP servers support sip: and sips: schemes. Check server capabilities with OPTIONS.