SIP 183 Session Progress vs 505 Version Not Supported
SIP 183 (Session Progress) is a 1xx Provisional response, while 505 (Version Not Supported) is a 5xx Server Failure 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, 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.
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 server does not support the SIP protocol version that was used in the request. Currently only SIP/2.0 is standardized.
Cuándo lo verás
Extremely rare. Would occur if a client sends a request with a SIP version other than 2.0.
Cómo solucionarlo
Ensure your UA uses SIP/2.0 in the request line. This is the only standardized version.
Diferencias clave
183 is a 1xx Provisional response, while 505 is a 5xx Server Failure 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 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 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 505 when extremely rare. Would occur if a client sends a request with a SIP version other than 2.0.
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 505 (Version Not Supported): Ensure your UA uses SIP/2.0 in the request line. This is the only standardized version.