SIP 180 Ringing vs 202 Accepted
SIP 180 (Ringing) is a 1xx Provisional response, while 202 (Accepted) is a 2xx Success response. 180 indicates that the UA receiving the INVITE is trying to alert the user. This response is used to initiate local ringback tone at the caller's end. In contrast, 202 means that the request has been accepted for processing but the processing has not been completed. Used primarily for REFER requests.
Description
The UA receiving the INVITE is trying to alert the user. This response is used to initiate local ringback tone at the caller's end.
When You See It
During call setup when the callee's phone is ringing. You should hear a ringback tone after receiving this response.
How to Fix
No fix needed — the callee's device is ringing. If the call never connects after ringing, check the callee's device or call forwarding settings.
Description
The request has been accepted for processing but the processing has not been completed. Used primarily for REFER requests.
When You See It
After sending a REFER request for call transfer. The transfer target acknowledges receipt but hasn't completed the transfer yet.
How to Fix
Wait for a NOTIFY to learn the outcome of the referred action. If no NOTIFY arrives, check subscription state and network connectivity.
Key Differences
180 is a 1xx Provisional response, while 202 is a 2xx Success response.
SIP 180: The UA receiving the INVITE is trying to alert the user. This response is used to initiate local ringback tone at the caller's end.
SIP 202: The request has been accepted for processing but the processing has not been completed. Used primarily for REFER requests.
You encounter 180 when during call setup when the callee's phone is ringing. You should hear a ringback tone after receiving this response.
You encounter 202 when after sending a REFER request for call transfer. The transfer target acknowledges receipt but hasn't completed the transfer yet.
When to Use Which
For 180 (Ringing): No fix needed — the callee's device is ringing. If the call never connects after ringing, check the callee's device or call forwarding settings. For 202 (Accepted): Wait for a NOTIFY to learn the outcome of the referred action. If no NOTIFY arrives, check subscription state and network connectivity.