SIP 100 Trying vs 481 Call/Transaction Does Not Exist
SIP 100 (Trying) is a 1xx Provisional response, while 481 (Call/Transaction Does Not Exist) is a 4xx Client Failure response. 100 indicates that the request has been received by the next-hop server and an unspecified action is being taken to process it. The UAC should expect additional responses. In contrast, 481 means that the UAS received a request that does not match any existing dialog or transaction. The call state may have been lost.
Mô tả
The request has been received by the next-hop server and an unspecified action is being taken to process it. The UAC should expect additional responses.
Khi bạn thấy mã này
Immediately after sending an INVITE. The proxy has received the call and is searching for the callee. This is the SIP equivalent of a dial tone.
Cách khắc phục
No fix needed — this is normal call setup behavior. If stuck on 100 Trying for too long, check network connectivity and proxy configuration.
Mô tả
The UAS received a request that does not match any existing dialog or transaction. The call state may have been lost.
Khi bạn thấy mã này
When sending a BYE, re-INVITE, or UPDATE for a call that the server has no record of. Common after server restarts.
Cách khắc phục
The dialog has been lost. Terminate the local call state. For re-INVITE failures, re-establish the call from scratch.
Sự khác biệt chính
100 is a 1xx Provisional response, while 481 is a 4xx Client Failure response.
SIP 100: The request has been received by the next-hop server and an unspecified action is being taken to process it. The UAC should expect additional responses.
SIP 481: The UAS received a request that does not match any existing dialog or transaction. The call state may have been lost.
You encounter 100 when immediately after sending an INVITE. The proxy has received the call and is searching for the callee. This is the SIP equivalent of a dial tone.
You encounter 481 when when sending a BYE, re-INVITE, or UPDATE for a call that the server has no record of. Common after server restarts.
Khi nào dùng cái nào
For 100 (Trying): No fix needed — this is normal call setup behavior. If stuck on 100 Trying for too long, check network connectivity and proxy configuration. For 481 (Call/Transaction Does Not Exist): The dialog has been lost. Terminate the local call state. For re-INVITE failures, re-establish the call from scratch.