[reSIProcate] Question about scenario where DUM callbacks are not called for client INVITE

[Francis Joanis]

Hi guys,

(this is using resip 1.6)

Consider the following scenario:

- Alice INVITEs Bob
- Bob replies 100 Trying
- Alice CANCELs the call to Bob
- ...

The InviteSessionHandler onNewSession and onTerminated callbacks are never
called on Alice's side because Bob never replied anything greater than a 100
Trying. Note that onNewSession (and friends) are properly called for Bob.

This might not be a huge issue in an application that simply implements
Alice's side: since onNewSession is never called, it is "safe" to assume
that no application logic was really called (i.e. no application state
created, ...). This is because the call never actually happened as far as
the application is concerned, yet it is the application that created the
INVITE message and instructed DUM to send it.

However, suppose this is implemented into a B2BUA which implements both UAS
and UAC. If that B2BUA is driven by an application-level FSM, then the above
scenario might confuse it since it would have been expecting an
onNewSession/onTerminated for its UAC leg...

I haven't researched any "nice" solutions yet, I wanted to get your opinions
first.

Thanks :)

Francis
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