[asterisk-users] Does SIP limit to 3-way conference?

[Karl Fife]

> Cassius Smith wrote:
>> Hello all,
>> I'm in final testing stages and preparing training for a new Asterisk
>> rollout. I'm replacing a Cisco Call Manager system, and re-flashing
>> the 79x1 phones with SIP 8.5.2. With the SIP load and while in a call,
>> I use the "Confrn" softkey to invite other participants. I can add one
>> other participant
>
> I think the phone itself is limited to 3 calls per line.
>
> Doug

It's got nothing to do with SIP.  The phone itself is doing the audio 
mixing, and the phone is limiting you to 2 call legs (plus you, making a 
3-way call).  You don't usually see phones that will bridge more than 2 call 
legs because the required technical resources generally exceed those of the 
endpoint.

Some 'better' phones such as the Polycom Soundpoint IP 6xx series phones 
will mix as many as 3 call legs (plus you, making a 4-way call).  Still, the 
phone itself is bearing the burden of the audio mixing which explains the 
limitation.

To conference more than 4 parties, you need a conference bridge (such as 
MeetMe). However, you can get clever with Asterisk and allow your end-user 
to transfer calls directly to a MeetMe conference with a single keypress! 
You can enable your end-user to collect conference participants one-by-one, 
rather than burdening your called parties with the need to dial in to a 
special phone number with a special access code!

-Karl