SIP 180 Ringing vs 485 Ambiguous
SIP 180 (Ringing) is a 1xx Provisional response, while 485 (Ambiguous) is a 4xx Client Failure 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, 485 means that the Request-URI was ambiguous. The response body may contain a list of possible unambiguous addresses.
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-URI was ambiguous. The response body may contain a list of possible unambiguous addresses.
When You See It
When the destination address matches multiple users and the server cannot determine which one is intended.
How to Fix
Use a more specific SIP URI. Check the response body for a list of possible matches and select the correct one.
Key Differences
180 is a 1xx Provisional response, while 485 is a 4xx Client Failure 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 485: The Request-URI was ambiguous. The response body may contain a list of possible unambiguous addresses.
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 485 when when the destination address matches multiple users and the server cannot determine which one is intended.
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 485 (Ambiguous): Use a more specific SIP URI. Check the response body for a list of possible matches and select the correct one.