SIP 202 Accepted vs 480 Temporarily Unavailable
SIP 202 (Accepted) is a 2xx Success response, while 480 (Temporarily Unavailable) is a 4xx Client Failure response. 202 indicates that the request has been accepted for processing but the processing has not been completed. Used primarily for REFER requests. 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
The request has been accepted for processing but the processing has not been completed. Used primarily for REFER requests.
何时出现
After sending a REFER request for call transfer. The transfer target acknowledges receipt but hasn't completed the transfer yet.
如何修复
Wait for a NOTIFY to learn the outcome of the referred action. If no NOTIFY arrives, check subscription state and network connectivity.
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
202 is a 2xx Success response, while 480 is a 4xx Client Failure response.
SIP 202: The request has been accepted for processing but the processing has not been completed. Used primarily for REFER requests.
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 202 when after sending a REFER request for call transfer. The transfer target acknowledges receipt but hasn't completed the transfer yet.
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 202 (Accepted): Wait for a NOTIFY to learn the outcome of the referred action. If no NOTIFY arrives, check subscription state and network connectivity. 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.