SIP 183 Session Progress vs 604 Does Not Exist Anywhere
SIP 183 (Session Progress) is a 1xx Provisional response, while 604 (Does Not Exist Anywhere) is a 6xx Global 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, 604 means that the server has authoritative information that the user indicated in the Request-URI does not exist anywhere. Unlike 404, this is a definitive, global statement.
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 has authoritative information that the user indicated in the Request-URI does not exist anywhere. Unlike 404, this is a definitive, global statement.
このコードが表示される場合
When the user definitively does not exist on any server in the network. The server has authoritative knowledge, not just local.
解決方法
The user does not exist. Verify the SIP URI or phone number. Unlike 404, retrying on other servers will not help.
主な違い
183 is a 1xx Provisional response, while 604 is a 6xx Global 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 604: The server has authoritative information that the user indicated in the Request-URI does not exist anywhere. Unlike 404, this is a definitive, global statement.
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 604 when when the user definitively does not exist on any server in the network. The server has authoritative knowledge, not just local.
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 604 (Does Not Exist Anywhere): The user does not exist. Verify the SIP URI or phone number. Unlike 404, retrying on other servers will not help.