SIP 180 Ringing vs 181 Call Is Being Forwarded
Both SIP 180 (Ringing) and 181 (Call Is Being Forwarded) belong to the 1xx Provisional category. 180 indicates that the UA receiving the INVITE is trying to alert the user. This response is used to initiate local ringback tone at the caller's end. Meanwhile, 181 means that a proxy server may send this to indicate that the call is being forwarded to a different set of destinations.
説明
The UA receiving the INVITE is trying to alert the user. This response is used to initiate local ringback tone at the caller's end.
このコードが表示される場合
During call setup when the callee's phone is ringing. You should hear a ringback tone after receiving this response.
解決方法
No fix needed — the callee's device is ringing. If the call never connects after ringing, check the callee's device or call forwarding settings.
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.
主な違い
SIP 180: The UA receiving the INVITE is trying to alert the user. This response is used to initiate local ringback tone at the caller's end.
SIP 181: A proxy server may send this to indicate that the call is being forwarded to a different set of destinations.
You encounter 180 when during call setup when the callee's phone is ringing. You should hear a ringback tone after receiving this response.
You encounter 181 when when the callee has call forwarding enabled and the request is being redirected to another number or device.
どちらをいつ使うか
For 180 (Ringing): No fix needed — the callee's device is ringing. If the call never connects after ringing, check the callee's device or call forwarding settings. 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.