SIP 183 Session Progress vs 305 Use Proxy
SIP 183 (Session Progress) is a 1xx Provisional response, while 305 (Use Proxy) is a 3xx Redirection 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, 305 means that the requested resource must be accessed through the proxy given by the Contact header field.
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 requested resource must be accessed through the proxy given by the Contact header field.
Cuándo lo verás
When the request must be routed through a specific outbound proxy server.
Cómo solucionarlo
Resend the request through the proxy specified in the Contact header of this response.
Diferencias clave
183 is a 1xx Provisional response, while 305 is a 3xx Redirection 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 305: The requested resource must be accessed through the proxy given by the Contact header field.
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 305 when when the request must be routed through a specific outbound proxy server.
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 305 (Use Proxy): Resend the request through the proxy specified in the Contact header of this response.