SIP 181 Call Is Being Forwarded vs 439 First Hop Lacks Outbound Support
SIP 181 (Call Is Being Forwarded) is a 1xx Provisional response, while 439 (First Hop Lacks Outbound Support) 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, 439 means that the first outbound proxy does not support the SIP outbound mechanism (RFC 5626) that the UA is trying to use.
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 first outbound proxy does not support the SIP outbound mechanism (RFC 5626) that the UA is trying to use.
Cuándo lo verás
When a UA configured for SIP outbound connects to a proxy that doesn't support the outbound option-tag.
Cómo solucionarlo
Upgrade the outbound proxy to support RFC 5626, or configure the UA to not require outbound support.
Diferencias clave
181 is a 1xx Provisional response, while 439 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 439: The first outbound proxy does not support the SIP outbound mechanism (RFC 5626) that the UA is trying to use.
You encounter 181 when when the callee has call forwarding enabled and the request is being redirected to another number or device.
You encounter 439 when when a UA configured for SIP outbound connects to a proxy that doesn't support the outbound option-tag.
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 439 (First Hop Lacks Outbound Support): Upgrade the outbound proxy to support RFC 5626, or configure the UA to not require outbound support.