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.
Описание
The address in the request resolved to several choices, each with its own location. The user or UA can select a preferred communication endpoint.
Когда вы это видите
When a user has multiple registered devices or contact addresses and the server cannot determine which one to use.
Как исправить
Select one of the provided Contact addresses and resend the request to that specific URI.
Описание
The request was received by a UAS that had a pending request within the same dialog. The UAS cannot process both requests simultaneously.
Когда вы это видите
When sending a re-INVITE while another re-INVITE is still being processed. Common during hold/unhold or codec change sequences.
Как исправить
Wait for the pending transaction to complete before sending a new one. Implement proper glare handling (RFC 3261 Section 14.1).
Ключевые различия
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.
Когда что использовать
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).