SIP 181 Call Is Being Forwarded vs 305 Use Proxy
SIP 181 (Call Is Being Forwarded) is a 1xx Provisional response, while 305 (Use Proxy) is a 3xx Redirection 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, 305 means that the requested resource must be accessed through the proxy given by the Contact header field.
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 requested resource must be accessed through the proxy given by the Contact header field.
When You See It
When the request must be routed through a specific outbound proxy server.
How to Fix
Resend the request through the proxy specified in the Contact header of this response.
Key Differences
181 is a 1xx Provisional response, while 305 is a 3xx Redirection response.
SIP 181: A proxy server may send this to indicate that the call is being forwarded to a different set of destinations.
SIP 305: The requested resource must be accessed through the proxy given by the Contact header field.
You encounter 181 when when the callee has call forwarding enabled and the request is being redirected to another number or device.
You encounter 305 when when the request must be routed through a specific outbound proxy server.
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 305 (Use Proxy): Resend the request through the proxy specified in the Contact header of this response.