[Serusers] How to drop a redundant/broken SIP reply message?

[Frank Durda IV]

Hendrik Scholz wrote:
>
> I'd call that expected behaviour ;)

For all-SIP environments it may be expected, but for
traditional ISUP/TDM networks, it is bad bad unacceptable
bad bad bad.  Did I mention bad?  

It is guaranteed to create trouble tickets.  These carriers
(including most of the North American cell phone
companies) don't care if there is a SIP leg in the call
somewhere where such behavior would be considered "okay".
As far as traditional phone service is concerned, you are
not allowed to give contra-indications to subscribers.
It can't be ringing and busy.  Choose one.

By the way, on most cell phone networks in North America,
if the called party elects to not take the call by hitting
the ignore button, the call goes to voicemail, and so the
ring-back you got to that point is consistent.   If the
called party doesn't have voicemail, you go to a recording.
Again, the treatment the subscriber hears is consistent
and you aren't presented with a busy or fast busy follwing
ring-back, except in cases of malfunction.  Either of
those showing up after ring-back almost always causes a
trouble ticket.

What is allowed elsewhere may vary, but they are pretty
strict about this sort of thing.

So I still have to come up with a fix or not allow the
calls to pass via SIP.  It is a pretty clear-cut requirement.