SIP 100 Trying vs 181 Call Is Being Forwarded
Both SIP 100 (Trying) and 181 (Call Is Being Forwarded) belong to the 1xx Provisional category. 100 indicates that the request has been received by the next-hop server and an unspecified action is being taken to process it. The UAC should expect additional responses. Meanwhile, 181 means that a proxy server may send this to indicate that the call is being forwarded to a different set of destinations.
描述
The request has been received by the next-hop server and an unspecified action is being taken to process it. The UAC should expect additional responses.
何时出现
Immediately after sending an INVITE. The proxy has received the call and is searching for the callee. This is the SIP equivalent of a dial tone.
如何修复
No fix needed — this is normal call setup behavior. If stuck on 100 Trying for too long, check network connectivity and proxy configuration.
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.
主要区别
SIP 100: The request has been received by the next-hop server and an unspecified action is being taken to process it. The UAC should expect additional responses.
SIP 181: A proxy server may send this to indicate that the call is being forwarded to a different set of destinations.
You encounter 100 when immediately after sending an INVITE. The proxy has received the call and is searching for the callee. This is the SIP equivalent of a dial tone.
You encounter 181 when when the callee has call forwarding enabled and the request is being redirected to another number or device.
何时使用哪个
For 100 (Trying): No fix needed — this is normal call setup behavior. If stuck on 100 Trying for too long, check network connectivity and proxy configuration. 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.