SIP 183 Session Progress vs 486 Busy Here
SIP 183 (Session Progress) is a 1xx Provisional response, while 486 (Busy Here) 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, 486 means that the callee's end system was contacted successfully but the callee is currently not willing or able to take additional calls at this end system.
Описание
Used to convey information about the progress of the call that is not otherwise classified. Often carries early media (ringback tones, announcements) via SDP.
Когда вы это видите
During call setup, especially in PSTN interworking scenarios. The response may contain SDP for early media like custom ringback tones or IVR prompts.
Как исправить
No fix needed — this is informational. If early media is not playing, check codec negotiation and SDP handling in your UA.
Описание
The callee's end system was contacted successfully but the callee is currently not willing or able to take additional calls at this end system.
Когда вы это видите
When the callee is already on a call and does not have call waiting. The user explicitly rejected the call, or all lines are in use.
Как исправить
Wait and try again later. The callee may become available when their current call ends. Consider leaving a voicemail if available.
Ключевые различия
183 is a 1xx Provisional response, while 486 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 486: The callee's end system was contacted successfully but the callee is currently not willing or able to take additional calls at this end system.
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 486 when when the callee is already on a call and does not have call waiting. The user explicitly rejected the call, or all lines are in use.
Когда что использовать
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 486 (Busy Here): Wait and try again later. The callee may become available when their current call ends. Consider leaving a voicemail if available.