SIP 100 Trying vs 501 Not Implemented
SIP 100 (Trying) is a 1xx Provisional response, while 501 (Not Implemented) is a 5xx Server Failure response. 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. In contrast, 501 means that the server does not support the functionality required to fulfill the request. The method is recognized but not implemented.
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
The server does not support the functionality required to fulfill the request. The method is recognized but not implemented.
Quand vous le voyez
When the SIP method is valid but the server has not implemented it (e.g., INFO, UPDATE, PRACK on a basic server).
Comment résoudre
Use a different method that the server supports. Check the Allow header in responses to see supported methods.
Différences clés
100 is a 1xx Provisional response, while 501 is a 5xx Server Failure response.
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 501: The server does not support the functionality required to fulfill the request. The method is recognized but not implemented.
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 501 when when the SIP method is valid but the server has not implemented it (e.g., INFO, UPDATE, PRACK on a basic server).
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 501 (Not Implemented): Use a different method that the server supports. Check the Allow header in responses to see supported methods.