[SIPForum-discussion] SIP conference call

mehmet eng.mehmetozi at gmail.com
Tue Sep 27 06:26:56 UTC 2011


Firstly assume that one call in hold and other is active.
Initiator first sends re-invite for hold to the active call.Then sends
INVITE to the server with the conference-uri in  the request line.Then sever
creates focus and sends 200 OK indicating with "isfocus" string in the
contact header.Also sends a specific conference uri inside the contact
header which belongs to this connference.
Then initiator sends two REFER messages to the held phones, to transfer the
conference.Again configures the "Refer-to" header with the specific
conference-uri and "isfocus" string.
Now when the server recevied both these REFER messages, it can act as B2BUA,
and sends two held phones re-invite indication with "isfocus" string.
And server returns the correct responses for the REFER messages as it the
other phones received the REFER and returned successfull responses.
Then after successfull negotiaons all three phones sends SUBSCRIBE messages
to subscribe to focus in order to receive the changes belonged to the
Now conference has been created.

I hope this explanation would be helpfull :)
Beside this I suggest to read http://www.packetizer.com/rfc/rfc4353/ (A
Framework for Conferencing with the Session Initiation Protocol (SIP)

Best Regards.

2011/9/25 Enthiran k <enthirann100 at gmail.com>

> Hi
> It would be great if any one can respond me immediately
> am having two legs and both are in held state.. ( or one in held and other
> in active )  now when i press the conference button what message would go
> ??
> cosidering the user is not a media mixer and thats done only by his SIP
> proxy.
> i want to understand exactly what message will be sent when i press the
> conference button ??:
> plss help
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