SIP 183 Session Progress vs 482 Loop Detected
SIP 183 (Session Progress) is a 1xx Provisional response, while 482 (Loop Detected) is a 4xx Client 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, 482 means that the server has detected a loop. The request was received with its own address in the Via header, indicating it has been forwarded back to itself.
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 has detected a loop. The request was received with its own address in the Via header, indicating it has been forwarded back to itself.
Cuándo lo verás
When routing configuration causes a request to cycle between two or more proxies without reaching the callee.
Cómo solucionarlo
Review proxy routing tables and DNS records. Check for circular references in SIP routing. Fix the routing configuration to break the loop.
Diferencias clave
183 is a 1xx Provisional response, while 482 is a 4xx Client 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 482: The server has detected a loop. The request was received with its own address in the Via header, indicating it has been forwarded back to itself.
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 482 when when routing configuration causes a request to cycle between two or more proxies without reaching the callee.
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 482 (Loop Detected): Review proxy routing tables and DNS records. Check for circular references in SIP routing. Fix the routing configuration to break the loop.