Should crossed BYEs generate 481s?
I thought so, because the sender forgets the dialog when it sends the BYE.
But I ran into someone who thought it should be 200s.
-troy
Most people responded that crossed BYEs should return 200.
I agree that it depends on whether the dialog still exists. But I think the RFC is less than clear about when the dialog goes away, when sending the BYE or when receiving the response. (The argument that the dialog exists because the transaction exists doesn't work for me. The dialog did not exist for all of the initial INVITE transaction.)
Consider 12.2.1
For INVITE initiated dialogs, terminating the dialog consists of sending a BYE.
section 15
The state of the session and the state of the dialog are very closely related.
and 15.1.1
Once the BYE is constructed, the UAC core creates a new non-INVITE client transaction, and passes it the BYE request. The UAC MUST consider the session terminated (and therefore stop sending or listening for media) as soon as the BYE request is passed to the client transaction. If the response for the BYE is a 481 (Call/Transaction Does Not Exist) or a 408 (Request Timeout) or no response at all is received for the BYE (that is, a timeout is returned by the client transaction), the UAC MUST consider the session and the dialog terminated.
Note that the first part of the above paragraph says the *session* is terminated, not the dialog. One could argue that the last sentence implies the dialog is not terminated until a response or timeout. But I think that that is inferring a lot.
If you're sure of your answer, 200 or 481, please supply a quote.
Anyway, here's my real follow up question. If the dialog still exists between the time a UA sends a BYE and gets a response, what happens to other dialog/session affecting requests, such as re-INVITE during that period?
That is, what happens when a BYE and a re-INVITE cross? Crossed re-INVITEs have 491 & a retry strategy, but that's specifically for crossed re-INVITES.
If my UA has sent a BYE, it has stopped sending or listening for media. What will a re-INVITE mean then? Could it restart media?
Thanks, -troy
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