SIP 100 Trying vs 505 Version Not Supported
SIP 100 (Trying) is a 1xx Provisional response, while 505 (Version Not Supported) 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, 505 means that the server does not support the SIP protocol version that was used in the request. Currently only SIP/2.0 is standardized.
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 SIP protocol version that was used in the request. Currently only SIP/2.0 is standardized.
Quand vous le voyez
Extremely rare. Would occur if a client sends a request with a SIP version other than 2.0.
Comment résoudre
Ensure your UA uses SIP/2.0 in the request line. This is the only standardized version.
Différences clés
100 is a 1xx Provisional response, while 505 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 505: The server does not support the SIP protocol version that was used in the request. Currently only SIP/2.0 is standardized.
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 505 when extremely rare. Would occur if a client sends a request with a SIP version other than 2.0.
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 505 (Version Not Supported): Ensure your UA uses SIP/2.0 in the request line. This is the only standardized version.