SIP 181 Call Is Being Forwarded vs 481 Call/Transaction Does Not Exist
SIP 181 (Call Is Being Forwarded) is a 1xx Provisional response, while 481 (Call/Transaction Does Not Exist) 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, 481 means that the UAS received a request that does not match any existing dialog or transaction. The call state may have been lost.
説明
A proxy server may send this to indicate that the call is being forwarded to a different set of destinations.
このコードが表示される場合
When the callee has call forwarding enabled and the request is being redirected to another number or device.
解決方法
No action needed. The call is being redirected. If forwarding is unintended, the callee should update their forwarding settings.
説明
The UAS received a request that does not match any existing dialog or transaction. The call state may have been lost.
このコードが表示される場合
When sending a BYE, re-INVITE, or UPDATE for a call that the server has no record of. Common after server restarts.
解決方法
The dialog has been lost. Terminate the local call state. For re-INVITE failures, re-establish the call from scratch.
主な違い
181 is a 1xx Provisional response, while 481 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 481: The UAS received a request that does not match any existing dialog or transaction. The call state may have been lost.
You encounter 181 when when the callee has call forwarding enabled and the request is being redirected to another number or device.
You encounter 481 when when sending a BYE, re-INVITE, or UPDATE for a call that the server has no record of. Common after server restarts.
どちらをいつ使うか
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 481 (Call/Transaction Does Not Exist): The dialog has been lost. Terminate the local call state. For re-INVITE failures, re-establish the call from scratch.