SIP 180 Ringing vs 502 Bad Gateway
SIP 180 (Ringing) is a 1xx Provisional response, while 502 (Bad Gateway) 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, 502 means that the server, acting as a gateway or proxy, received an invalid response from a downstream server it accessed in attempting to fulfill the request.
Description
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.
When You See It
During call setup when the callee's phone is ringing. You should hear a ringback tone after receiving this response.
How to Fix
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.
Description
The server, acting as a gateway or proxy, received an invalid response from a downstream server it accessed in attempting to fulfill the request.
When You See It
When a SIP proxy receives a malformed or invalid response from the next-hop server. Common in interop scenarios between different vendors.
How to Fix
Check the downstream server's health and configuration. Verify SIP message formatting between the two servers. Review network connectivity.
Key Differences
180 is a 1xx Provisional response, while 502 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 502: The server, acting as a gateway or proxy, received an invalid response from a downstream server it accessed in attempting to fulfill the request.
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 502 when when a SIP proxy receives a malformed or invalid response from the next-hop server. Common in interop scenarios between different vendors.
When to Use Which
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 502 (Bad Gateway): Check the downstream server's health and configuration. Verify SIP message formatting between the two servers. Review network connectivity.