[reSIProcate] CANCEL and Early Media

[Nilay Tripathi]

Hi,

Scenario:
Our DUM is UAC !

1. UAC makes a call to UAS with SDP Offer.
2. UAS responds SDP Answer in rel. 1xx. UAS starts Early media.
3. UAC is able to play the early media.
4. UAC disconnects the call - sends CANCEL. State is transitioned to
"UAC_Cancelled"

Now, 200 OK (CANCEL) is received and is discarded at
DialogUsageManager::processResponse().
When UAS sends a 487, it reaches ClientInviteSession::dispatchCancelled()
and the dialog gets destroyed.

Prob 1: If any other 4xx message comes (apart from 422, 487), the event
would be "OnInviteFailure", which is not catered in dispatchCancelled and,
therefore, onTerminated callback is not called to apprise user of call
disconnect. This will only happen once the Cancelled timer fires and until
then (32 sec) the media streams keep on playing.

For that "OnInviteFailure" should also be added.

Query 1: I could not understand how the ACK is going in this case. It is
certainly not triggered by the DUM and is done by stack. Appreciate any
inputs on this as well.

Query 2: We are just ignoring 200 OK (CANCEL) in dum. Since ACK is anyway
going to be sent from Stack, why don't we finish the dialog on receiving 200
OK (CANCEL).

Similar ideas are already floating on the mailing list, perhaps this can be
taken as a use-case for that argument :)

Thanks 'n' Regards,
Nilay
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