What it means
The call is progressing and early media may be flowing before the call is answered. Carriers use it to play ringback, announcements, or failure messages down the audio path before a 200 OK.
SIP/2.0 183 Session Progress
Common causes
- The carrier is sending early media such as ringback or an announcement
- A gateway wants you to hear a tone or message before answer
How to fix it
- Usually normal. If you hear a carrier announcement then the call fails, the real reason is in the message the carrier plays or the final response that follows
- If early media is silent, check that your SDP in the 183 is honored and the RTP path is open
See it in your own trace
Paste a full SIP or Asterisk log into the decoder and ladder tools to see exactly where this response appears in the call and what led to it. Everything runs in your browser, so your logs never leave your device.
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See how a SIP call flows