SIP 204 No Notification vs 491 Request Pending
SIP 204 (No Notification) is a 2xx Success response, while 491 (Request Pending) is a 4xx Client 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, 491 means that the request was received by a UAS that had a pending request within the same dialog. The UAS cannot process both requests simultaneously.
विवरण
The request was successful but the server has decided not to send a NOTIFY for this SUBSCRIBE request.
जब आप इसे देखें
When subscribing to event packages that may not generate immediate notifications, such as dialog or presence packages.
कैसे ठीक करें
No fix needed. The subscription was accepted but there is no state change to notify about yet.
विवरण
The request was received by a UAS that had a pending request within the same dialog. The UAS cannot process both requests simultaneously.
जब आप इसे देखें
When sending a re-INVITE while another re-INVITE is still being processed. Common during hold/unhold or codec change sequences.
कैसे ठीक करें
Wait for the pending transaction to complete before sending a new one. Implement proper glare handling (RFC 3261 Section 14.1).
मुख्य अंतर
204 is a 2xx Success response, while 491 is a 4xx Client Failure response.
SIP 204: The request was successful but the server has decided not to send a NOTIFY for this SUBSCRIBE request.
SIP 491: The request was received by a UAS that had a pending request within the same dialog. The UAS cannot process both requests simultaneously.
You encounter 204 when when subscribing to event packages that may not generate immediate notifications, such as dialog or presence packages.
You encounter 491 when when sending a re-INVITE while another re-INVITE is still being processed. Common during hold/unhold or codec change sequences.
कब किसका उपयोग करें
For 204 (No Notification): No fix needed. The subscription was accepted but there is no state change to notify about yet. For 491 (Request Pending): Wait for the pending transaction to complete before sending a new one. Implement proper glare handling (RFC 3261 Section 14.1).