SIP 183 Session Progress vs 606 Not Acceptable
SIP 183 (Session Progress) is a 1xx Provisional response, while 606 (Not Acceptable) is a 6xx Global 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, 606 means that the user's agent was contacted successfully but some aspects of the session description (SDP) are not acceptable. Unlike 488, this is a global failure — no other server can satisfy this request.
Описание
Used to convey information about the progress of the call that is not otherwise classified. Often carries early media (ringback tones, announcements) via SDP.
Когда вы это видите
During call setup, especially in PSTN interworking scenarios. The response may contain SDP for early media like custom ringback tones or IVR prompts.
Как исправить
No fix needed — this is informational. If early media is not playing, check codec negotiation and SDP handling in your UA.
Описание
The user's agent was contacted successfully but some aspects of the session description (SDP) are not acceptable. Unlike 488, this is a global failure — no other server can satisfy this request.
Когда вы это видите
When the callee definitively cannot accept any of the offered media types or codecs. Different from 488 which is location-specific.
Как исправить
Check the Warning header or response body for which session parameters are unacceptable. Modify the SDP offer to use compatible codecs and media types.
Ключевые различия
183 is a 1xx Provisional response, while 606 is a 6xx Global 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 606: The user's agent was contacted successfully but some aspects of the session description (SDP) are not acceptable. Unlike 488, this is a global failure — no other server can satisfy this 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 606 when when the callee definitively cannot accept any of the offered media types or codecs. Different from 488 which is location-specific.
Когда что использовать
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 606 (Not Acceptable): Check the Warning header or response body for which session parameters are unacceptable. Modify the SDP offer to use compatible codecs and media types.