SIP 181 Call Is Being Forwarded vs 488 Not Acceptable Here
SIP 181 (Call Is Being Forwarded) is a 1xx Provisional response, while 488 (Not Acceptable Here) 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, 488 means that the request was understood but the session description (SDP) is not acceptable. The response may contain a list of acceptable media parameters.
描述
A proxy server may send this to indicate that the call is being forwarded to a different set of destinations.
何时出现
When the callee has call forwarding enabled and the request is being redirected to another number or device.
如何修复
No action needed. The call is being redirected. If forwarding is unintended, the callee should update their forwarding settings.
描述
The request was understood but the session description (SDP) is not acceptable. The response may contain a list of acceptable media parameters.
何时出现
When codec negotiation fails — the callee cannot handle any of the codecs offered in the SDP. Common in interop scenarios.
如何修复
Check the Warning header or SDP in the response for acceptable parameters. Add compatible codecs (e.g., G.711 as a fallback) to your offer.
主要区别
181 is a 1xx Provisional response, while 488 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 488: The request was understood but the session description (SDP) is not acceptable. The response may contain a list of acceptable media parameters.
You encounter 181 when when the callee has call forwarding enabled and the request is being redirected to another number or device.
You encounter 488 when when codec negotiation fails — the callee cannot handle any of the codecs offered in the SDP. Common in interop scenarios.
何时使用哪个
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 488 (Not Acceptable Here): Check the Warning header or SDP in the response for acceptable parameters. Add compatible codecs (e.g., G.711 as a fallback) to your offer.