SIP 180 Ringing vs 415 Unsupported Media Type
SIP 180 (Ringing) is a 1xx Provisional response, while 415 (Unsupported Media Type) 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, 415 means that the server is refusing the request because the message body is in a format not supported by the server for the requested method.
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 server is refusing the request because the message body is in a format not supported by the server for the requested method.
When You See It
When the Content-Type of the request body is not supported. For INVITE, this often means an unsupported SDP format.
How to Fix
Check the Accept header in the response to see supported media types. Use a compatible Content-Type in your request.
Key Differences
180 is a 1xx Provisional response, while 415 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 415: The server is refusing the request because the message body is in a format not supported by the server for the requested method.
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 415 when when the Content-Type of the request body is not supported. For INVITE, this often means an unsupported SDP format.
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 415 (Unsupported Media Type): Check the Accept header in the response to see supported media types. Use a compatible Content-Type in your request.