SIP 181 Call Is Being Forwarded vs 430 Flow Failed
SIP 181 (Call Is Being Forwarded) is a 1xx Provisional response, while 430 (Flow Failed) 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, 430 means that the specific flow to a user agent has failed but other flows may succeed. Used with SIP outbound (RFC 5626).
Description
A proxy server may send this to indicate that the call is being forwarded to a different set of destinations.
When You See It
When the callee has call forwarding enabled and the request is being redirected to another number or device.
How to Fix
No action needed. The call is being redirected. If forwarding is unintended, the callee should update their forwarding settings.
Description
The specific flow to a user agent has failed but other flows may succeed. Used with SIP outbound (RFC 5626).
When You See It
When using SIP outbound connections and the specific TCP/TLS connection (flow) to the UA has been lost.
How to Fix
The proxy should attempt delivery via other registered flows. The UA should re-register to establish a new flow.
Key Differences
181 is a 1xx Provisional response, while 430 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 430: The specific flow to a user agent has failed but other flows may succeed. Used with SIP outbound (RFC 5626).
You encounter 181 when when the callee has call forwarding enabled and the request is being redirected to another number or device.
You encounter 430 when when using SIP outbound connections and the specific TCP/TLS connection (flow) to the UA has been lost.
When to Use Which
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 430 (Flow Failed): The proxy should attempt delivery via other registered flows. The UA should re-register to establish a new flow.