SIP 300 Multiple Choices vs 491 Request Pending
SIP 300 (Multiple Choices) is a 3xx Redirection response, while 491 (Request Pending) is a 4xx Client Failure response. 300 indicates that the address in the request resolved to several choices, each with its own location. The user or UA can select a preferred communication endpoint. 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.
説明
The address in the request resolved to several choices, each with its own location. The user or UA can select a preferred communication endpoint.
このコードが表示される場合
When a user has multiple registered devices or contact addresses and the server cannot determine which one to use.
解決方法
Select one of the provided Contact addresses and resend the request to that specific URI.
説明
The request was received by a UAS that had a pending request within the same dialog. The UAS cannot process both requests simultaneously.
このコードが表示される場合
When sending a re-INVITE while another re-INVITE is still being processed. Common during hold/unhold or codec change sequences.
解決方法
Wait for the pending transaction to complete before sending a new one. Implement proper glare handling (RFC 3261 Section 14.1).
主な違い
300 is a 3xx Redirection response, while 491 is a 4xx Client Failure response.
SIP 300: The address in the request resolved to several choices, each with its own location. The user or UA can select a preferred communication endpoint.
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 300 when when a user has multiple registered devices or contact addresses and the server cannot determine which one to use.
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.
どちらをいつ使うか
For 300 (Multiple Choices): Select one of the provided Contact addresses and resend the request to that specific URI. 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).