[VoIP] Congestion vs Hangup in Asterisk

[John R. Covert]

On July 18th I posted an article which addressed Congestion(),
among other related things.  The Subject was "Congestion and Busy
Handling."

In that article, I pointed out that different technologies handle
things differently.  The "Busy()" and "Congestion()" applications
do not apply any tones to an analogue circuit or even a CAS (as
opposed to PRI) circuit; they simply sit there.  If you're coming
in on a SIP, IAX, or PRI channel, they send an appropriate result
code and wait until the originating party releases.  In any case,
since they wait, they can possibly leaving the channel connected
forever.

I provided a Macro called "fastbusy" which actually handles both
Busy and Congestion (and maybe a bit more), which I can invoke
after just about every Dial command or in other appropriate
explicit places.  It sends the tones for 10 seconds using the
Playtones() application, so that the originating party actually
hears some tones, regardless of the technology involved (such
as a softphone client that simply displays an error for five
seconds and then goes back to idle -- a caller might completely
miss that).  After sending the tones, it sets an absolute
timeout and issues either Congestion() or Busy().  The absolute
timeout clears the call if the caller doesn't hang up before
the timeout fires.

/john