SIP 204 No Notification vs 505 Version Not Supported
SIP 204 (No Notification) is a 2xx Success response, while 505 (Version Not Supported) is a 5xx Server Failure response. 204 indicates that the request was successful but the server has decided not to send a NOTIFY for this SUBSCRIBE request. In contrast, 505 means that the server does not support the SIP protocol version that was used in the request. Currently only SIP/2.0 is standardized.
Description
The request was successful but the server has decided not to send a NOTIFY for this SUBSCRIBE request.
When You See It
When subscribing to event packages that may not generate immediate notifications, such as dialog or presence packages.
How to Fix
No fix needed. The subscription was accepted but there is no state change to notify about yet.
Description
The server does not support the SIP protocol version that was used in the request. Currently only SIP/2.0 is standardized.
When You See It
Extremely rare. Would occur if a client sends a request with a SIP version other than 2.0.
How to Fix
Ensure your UA uses SIP/2.0 in the request line. This is the only standardized version.
Key Differences
204 is a 2xx Success response, while 505 is a 5xx Server Failure response.
SIP 204: The request was successful but the server has decided not to send a NOTIFY for this SUBSCRIBE request.
SIP 505: The server does not support the SIP protocol version that was used in the request. Currently only SIP/2.0 is standardized.
You encounter 204 when when subscribing to event packages that may not generate immediate notifications, such as dialog or presence packages.
You encounter 505 when extremely rare. Would occur if a client sends a request with a SIP version other than 2.0.
When to Use Which
For 204 (No Notification): No fix needed. The subscription was accepted but there is no state change to notify about yet. For 505 (Version Not Supported): Ensure your UA uses SIP/2.0 in the request line. This is the only standardized version.