Step 19. Conference

This is how a server conference is organized. Conferences on the server are divided into rooms having arbitrary numbers. The code of the subscriber function "conference" is configured in the number plan, for example, the number *95 is assigned to it. And routing rules suggest dialing numbers using the *95XXX mask. Thus, dialing the number *95123, the subscriber gets to the conference room with the number 123. If several domain subscribers call the same number, they will all be in the same conference room, i.e. they will be able to hear each other. Up to 250 participants can be served in a particular conference room. Even if there is more than one number in the dial plan for the "conference" subscriber feature code, such as *95 and #7, calling the numbers *95123 and #7123 will bring the domain users into the same conference room_.

A conference room always belongs to the domain in which the subscriber function code is configured, and is served at one of the sites served by that domain. The conference can also be accessed from another domain if cross-domain calls are configured accordingly. A Conference Room is created by the call of the first participant. Its service site becomes the site conditionally closest to the first participant. A second call to the same conference room will locate it at the site where it was created. The conference is destroyed automatically when the last participant leaves. The conference is limited in time, it has a 2-hour time limit, just like all calls.

Such conferences are served by conference servers, role CONF. It is reserved and scaled in Active-Active mode. This role is a SIP-UA, that is, a user-agent with respect to the call (B2B dialog). Communication between multiple subscribers to a conference room actually involves the same number of independent calls (B2B-dialogs). On a general basis, a conference can be transferred to a number or to another subscriber with spoofing, and conversely, any subscriber (also by number or with spoofing) can be transferred to a conference.

A server conference has its own media context on one of the adjacent media gateways. In general, each call is served by a media gateway, and the conference itself is served by a media gateway. It is the responsibility of the media gateway serving the context of the conference to mix the audio traffic for each of the conference participants so that they can hear everyone but themselves.

This method of conference organization is supported by most telephone devices. The peculiarity is that from the server’s point of view these are two independent calls, sound mixing is performed by the subscriber device itself, on which the CONF button was pressed. Two independent calls will also be detected in the call log, but in the call record each of them will contain in two channels the speech of all three subscribers.