SIP 202 Accepted vs 491 Request Pending
SIP 202 (Accepted) is a 2xx Success response, while 491 (Request Pending) is a 4xx Client Failure response. 202 indicates that the request has been accepted for processing but the processing has not been completed. Used primarily for REFER requests. 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.
Deskripsi
The request has been accepted for processing but the processing has not been completed. Used primarily for REFER requests.
Ketika Anda Melihatnya
After sending a REFER request for call transfer. The transfer target acknowledges receipt but hasn't completed the transfer yet.
Cara Memperbaiki
Wait for a NOTIFY to learn the outcome of the referred action. If no NOTIFY arrives, check subscription state and network connectivity.
Deskripsi
The request was received by a UAS that had a pending request within the same dialog. The UAS cannot process both requests simultaneously.
Ketika Anda Melihatnya
When sending a re-INVITE while another re-INVITE is still being processed. Common during hold/unhold or codec change sequences.
Cara Memperbaiki
Wait for the pending transaction to complete before sending a new one. Implement proper glare handling (RFC 3261 Section 14.1).
Perbedaan Utama
202 is a 2xx Success response, while 491 is a 4xx Client Failure response.
SIP 202: The request has been accepted for processing but the processing has not been completed. Used primarily for REFER requests.
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 202 when after sending a REFER request for call transfer. The transfer target acknowledges receipt but hasn't completed the transfer yet.
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.
Kapan Menggunakan Yang Mana
For 202 (Accepted): Wait for a NOTIFY to learn the outcome of the referred action. If no NOTIFY arrives, check subscription state and network connectivity. 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).