[Asterisk-Dev] Basic Conferencing from IAX2, other VoIP Channels

[Steven Sokol]

Asterisk's MeetMe is powerful and flexible, but sometimes you just want to
do an old-fashioned basic conference from the client, without having to
transfer everybody into a conference room.  This is pretty common
functionality on most office phone systems.

Scenario:

1.  You (party A) are on an active call with party B.
2.  You decide to add in another party (C).
3.  You key the CONF button on your business set.
	- Party B gets MOH or silence.
	- Party B's appearance on your phone goes to the HELD state.
	- You get new dial-tone on a new appearance
4.  You dial the number for party C.
5.  Party C answers and you communicate briefly.
6.  You press the CONF key again to establish the conference
	- The bridging takes place in the PBX/KSU
	- Party B is pulled out of MOH-land and added to the new call
	- Party B's appearance returns to the ACTIVE state

Now you are conferenced.  Both call appearances show active.  You can even
follow the same set of steps to conference in another user if you have
additional appearances on your set.

In Asterisk using most VoIP phones (soft or hard) this scenario does not
play out.  You wind up transferring party A into the MeetMe, calling party B
and transferring them into the MeetMe, then dialing into the MeetMe
yourself.

This is further complicated by the fact that any given static MeetMe may or
may not already be occupied by others doing the same thing.  Dynamic MeetMes
make this a bit more flexible, but there's little documentation to the
dynamic feature.

Is there an elegant way to execute dynamic conferencing in Asterisk?  Can
this be done without building conferencing logic into the client UA?  If so,
how?

If not (which I think is the case), how do we add this in?  I have a number
of clients using my IAX Phone who are not really happy about having to jump
through hoops to handle spontaneous conferences.

I would be happy to _try_ to code the solution into IAX2 (both chan_iax2 and
libiax2) if somebody can tell me where to begin.  I would think there has to
be some way to add in an IAX2 command to merge two calls or to command
Asterisk to bridge the calls at the server.

Also, is there a way execute such a conference from SIP, MGCP, H323, or
other protocols?  If so, who wants to implement it?

Any thoughts would be appreciated.  Apologies in advance if I missed some
really simple way of doing this.

Thanks,

Steve

Steven Sokol
Owner/Manager
Sokol & Associates, LLC

Phone:  816.822.1807
IaxTel: 700.613.9004
Web:    http://www.sokol-associates.com