SIP 100 Trying vs 423 Interval Too Brief
SIP 100 (Trying) is a 1xx Provisional response, while 423 (Interval Too Brief) is a 4xx Client 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, 423 means that the expiration time in the request is too short. The response contains a Min-Expires header indicating the minimum allowed value.
Descripción
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.
Cuándo lo verás
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.
Cómo solucionarlo
No fix needed — this is normal call setup behavior. If stuck on 100 Trying for too long, check network connectivity and proxy configuration.
Descripción
The expiration time in the request is too short. The response contains a Min-Expires header indicating the minimum allowed value.
Cuándo lo verás
When a REGISTER or SUBSCRIBE request has an Expires value that is below the server's minimum. Common with aggressive keep-alive timers.
Cómo solucionarlo
Increase the Expires header value to at least the Min-Expires value from the response.
Diferencias clave
100 is a 1xx Provisional response, while 423 is a 4xx Client 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 423: The expiration time in the request is too short. The response contains a Min-Expires header indicating the minimum allowed value.
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 423 when when a REGISTER or SUBSCRIBE request has an Expires value that is below the server's minimum. Common with aggressive keep-alive timers.
Cuándo usar cada uno
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 423 (Interval Too Brief): Increase the Expires header value to at least the Min-Expires value from the response.