SIP 183 Session Progress vs 415 Unsupported Media Type
SIP 183 (Session Progress) is a 1xx Provisional response, while 415 (Unsupported Media Type) is a 4xx Client 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, 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.
説明
Used to convey information about the progress of the call that is not otherwise classified. Often carries early media (ringback tones, announcements) via SDP.
このコードが表示される場合
During call setup, especially in PSTN interworking scenarios. The response may contain SDP for early media like custom ringback tones or IVR prompts.
解決方法
No fix needed — this is informational. If early media is not playing, check codec negotiation and SDP handling in your UA.
説明
The server is refusing the request because the message body is in a format not supported by the server for the requested method.
このコードが表示される場合
When the Content-Type of the request body is not supported. For INVITE, this often means an unsupported SDP format.
解決方法
Check the Accept header in the response to see supported media types. Use a compatible Content-Type in your request.
主な違い
183 is a 1xx Provisional response, while 415 is a 4xx Client 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 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 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 415 when when the Content-Type of the request body is not supported. For INVITE, this often means an unsupported SDP format.
どちらをいつ使うか
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 415 (Unsupported Media Type): Check the Accept header in the response to see supported media types. Use a compatible Content-Type in your request.