Page 82 and Page 83 of RFC-3261 and Section 9 would be helpful. Below is my
opinion
INVITE -----> -------------> INVITE
180 Ringing <-------- <----------- 180 Ringing
CANCEL ------> <----------- 200 OK for INVITE
------------> CANCEL
200OK (INV) <----------
----------------- GLARE OCCURRED --------------
Now at this point of time the UAC has two separate transactions ( INVITE and
CANCEL ), so it should complete the INVITE transaction by sending an ACK and
terminate the dialog by sending BYE. I do not think it has to wait for 200
OK for CANCEL to come back before sending ACK and BYE, as CANCEL is separate
transaction than the INVITE, even though it has same branch and for the
INVITE Transaction it has received an ACK ).
On the UAS side since CANCEL was received after sending 200 OK, UAS will
respond to it with 200 OK for CANCEL to successfully acknowledge receiving
the CANCEL, but not acting on it as it has already sent a final response to
the INVITE transaction for which CANCEL request was received )
<----------- 200 OK CANCEL
ACK ------------> ------------> ACK
200 OK CAN <------------
BYE ------------> -------------> BYE
200OK <----------- <------------ 200 OK
Please note that the 200 OK for CANCEL can be received event after UA has
sent BYE as these are separate transactions.
Regards,
Indresh K Singh
On 5/23/07, Justin Lu <[EMAIL PROTECTED]> wrote:
>
> It is said in Section 9 in 3261 that
>
> "In that usage, a UAS that receives a CANCEL request for an INVITE, but
> has not yet sent a final response, would "stop ringing", and then respond to
> the INVITE with a specific error response (a 487)."
>
> My question is what does the UAS do when it already sent out the final
> response (but not received by the UAC) and receives the CANCEL request?
>
> Justin
>
>
>
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