SIP 183 Session Progress vs 480 Temporarily Unavailable
SIP 183 (Session Progress) is a 1xx Provisional response, while 480 (Temporarily Unavailable) 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, 480 means that the callee's end system was contacted successfully but the callee is currently unavailable. The client may retry after some time.
描述
Used to convey information about the progress of the call that is not otherwise classified. Often carries early media (ringback tones, announcements) via SDP.
何时出现
During call setup, especially in PSTN interworking scenarios. The response may contain SDP for early media like custom ringback tones or IVR prompts.
如何修复
No fix needed — this is informational. If early media is not playing, check codec negotiation and SDP handling in your UA.
描述
The callee's end system was contacted successfully but the callee is currently unavailable. The client may retry after some time.
何时出现
When the user exists but is not currently reachable — phone is off, DND mode enabled, or all lines are busy.
如何修复
Try calling again later. Check if the callee has DND enabled or if their device is powered off. Configure voicemail for unavailable scenarios.
主要区别
183 is a 1xx Provisional response, while 480 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 480: The callee's end system was contacted successfully but the callee is currently unavailable. The client may retry after some time.
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 480 when when the user exists but is not currently reachable — phone is off, DND mode enabled, or all lines are busy.
何时使用哪个
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 480 (Temporarily Unavailable): Try calling again later. Check if the callee has DND enabled or if their device is powered off. Configure voicemail for unavailable scenarios.