SIP 480 Temporarily Unavailable vs 486 Busy Here
SIP 480 and 486 both mean the callee cannot take the call right now, but for different reasons. A 480 means the callee is unreachable (phone off, not registered, DND mode), while a 486 means the callee's device is actively busy on another call.
説明
The callee's end system was contacted successfully but the callee is currently unavailable. The client may retry after some time.
このコードが表示される場合
When the user exists but is not currently reachable — phone is off, DND mode enabled, or all lines are busy.
修正方法
Try calling again later. Check if the callee has DND enabled or if their device is powered off. Configure voicemail for unavailable scenarios.
説明
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.
このコードが表示される場合
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.
修正方法
Wait and try again later. The callee may become available when their current call ends. Consider leaving a voicemail if available.
主な違い
480 means the callee is not reachable at all — the device may be off, unregistered, or in DND mode.
486 means the callee's line is busy — they are actively on another call at this specific endpoint.
480 may trigger voicemail or call forwarding; 486 may trigger call waiting if enabled.
486 is specific to one endpoint; if the user has multiple devices, the call may succeed on another (use 600 for all busy).
Retry behavior differs: 480 may resolve after the user comes back online; 486 resolves when the current call ends.
使い分け方
Return 480 when the callee cannot be reached — their device is offline, not registered with the registrar, or they have enabled Do Not Disturb. Return 486 when the callee's endpoint is actively engaged in another call. Call routing logic should handle both: 480 may route to voicemail, while 486 may trigger call waiting.