SIP 302 Moved Temporarily vs 481 Call/Transaction Does Not Exist
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SIP 302 (Moved Temporarily) is a 3xx Redirection response, while 481 (Call/Transaction Does Not Exist) is a 4xx Client Failure response. 302 indicates that the callee has temporarily moved to a different address. The client should retry the request at the Contact address but continue using the original URI for future requests. 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.
Description
The callee has temporarily moved to a different address. The client should retry the request at the Contact address but continue using the original URI for future requests.
When You See It
When a user is temporarily reachable at a different location, such as when traveling or using a different device.
How to Fix
Redirect the current call to the Contact URI provided, but keep the original URI for future requests.
Description
The UAS received a request that does not match any existing dialog or transaction. The call state may have been lost.
When You See It
When sending a BYE, re-INVITE, or UPDATE for a call that the server has no record of. Common after server restarts.
How to Fix
The dialog has been lost. Terminate the local call state. For re-INVITE failures, re-establish the call from scratch.
Key Differences
302 is a 3xx Redirection response, while 481 is a 4xx Client Failure response.
SIP 302: The callee has temporarily moved to a different address. The client should retry the request at the Contact address but continue using the original URI for future requests.
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 302 when when a user is temporarily reachable at a different location, such as when traveling or using a different device.
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.
When to Use Which
For 302 (Moved Temporarily): Redirect the current call to the Contact URI provided, but keep the original URI for future requests. 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.