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.
Description
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.
Quand vous le voyez
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.
Comment résoudre
No fix needed — this is normal call setup behavior. If stuck on 100 Trying for too long, check network connectivity and proxy configuration.
Description
A proxy server may send this to indicate that the call is being forwarded to a different set of destinations.
Quand vous le voyez
When the callee has call forwarding enabled and the request is being redirected to another number or device.
Comment résoudre
No action needed. The call is being redirected. If forwarding is unintended, the callee should update their forwarding settings.
Différences clés
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.
Quand utiliser lequel
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.