SIP 183 Session Progress vs 204 No Notification
SIP 183 (Session Progress) is a 1xx Provisional response, while 204 (No Notification) is a 2xx Success response. 183 indicates that used to convey information about the progress of the call that is not otherwise classified. Often carries early media (ringback tones, announcements) via SDP. In contrast, 204 means that the request was successful but the server has decided not to send a NOTIFY for this SUBSCRIBE request.
Descripción
Used to convey information about the progress of the call that is not otherwise classified. Often carries early media (ringback tones, announcements) via SDP.
Cuándo lo verás
During call setup, especially in PSTN interworking scenarios. The response may contain SDP for early media like custom ringback tones or IVR prompts.
Cómo solucionarlo
No fix needed — this is informational. If early media is not playing, check codec negotiation and SDP handling in your UA.
Descripción
The request was successful but the server has decided not to send a NOTIFY for this SUBSCRIBE request.
Cuándo lo verás
When subscribing to event packages that may not generate immediate notifications, such as dialog or presence packages.
Cómo solucionarlo
No fix needed. The subscription was accepted but there is no state change to notify about yet.
Diferencias clave
183 is a 1xx Provisional response, while 204 is a 2xx Success response.
SIP 183: Used to convey information about the progress of the call that is not otherwise classified. Often carries early media (ringback tones, announcements) via SDP.
SIP 204: The request was successful but the server has decided not to send a NOTIFY for this SUBSCRIBE request.
You encounter 183 when during call setup, especially in PSTN interworking scenarios. The response may contain SDP for early media like custom ringback tones or IVR prompts.
You encounter 204 when when subscribing to event packages that may not generate immediate notifications, such as dialog or presence packages.
Cuándo usar cada uno
For 183 (Session Progress): No fix needed — this is informational. If early media is not playing, check codec negotiation and SDP handling in your UA. For 204 (No Notification): No fix needed. The subscription was accepted but there is no state change to notify about yet.