SIP 180 Ringing vs 503 Service Unavailable
SIP 180 (Ringing) is a 1xx Provisional response, while 503 (Service Unavailable) is a 5xx Server Failure response. 180 indicates that the UA receiving the INVITE is trying to alert the user. This response is used to initiate local ringback tone at the caller's end. In contrast, 503 means that the server is temporarily unable to process the request due to overloading or maintenance. The client should retry after the time indicated in the Retry-After header.
描述
The UA receiving the INVITE is trying to alert the user. This response is used to initiate local ringback tone at the caller's end.
何时出现
During call setup when the callee's phone is ringing. You should hear a ringback tone after receiving this response.
如何修复
No fix needed — the callee's device is ringing. If the call never connects after ringing, check the callee's device or call forwarding settings.
描述
The server is temporarily unable to process the request due to overloading or maintenance. The client should retry after the time indicated in the Retry-After header.
何时出现
During server overload, maintenance windows, or when the server is rate-limiting requests. Common during traffic spikes.
如何修复
Wait for the time specified in the Retry-After header. If persistent, check server capacity and consider load balancing across multiple SIP proxies.
主要区别
180 is a 1xx Provisional response, while 503 is a 5xx Server Failure response.
SIP 180: The UA receiving the INVITE is trying to alert the user. This response is used to initiate local ringback tone at the caller's end.
SIP 503: The server is temporarily unable to process the request due to overloading or maintenance. The client should retry after the time indicated in the Retry-After header.
You encounter 180 when during call setup when the callee's phone is ringing. You should hear a ringback tone after receiving this response.
You encounter 503 when during server overload, maintenance windows, or when the server is rate-limiting requests. Common during traffic spikes.
何时使用哪个
For 180 (Ringing): No fix needed — the callee's device is ringing. If the call never connects after ringing, check the callee's device or call forwarding settings. For 503 (Service Unavailable): Wait for the time specified in the Retry-After header. If persistent, check server capacity and consider load balancing across multiple SIP proxies.