User`s manual

Version 5.4 475 May 2008

SIP User's Manual 10. Media Server Capabilities

Figure 10-4: Applying Media Services on a Conference -- SIP Call Flow

10.1.2.5 Active Speaker Notification

After an advanced conference is established, the Application Server can subscribe to the

device to receive notifications of the current set of active speakers in a conference at any

given moment. This feature is referred to as Active Speaker Notification (ASN) and is

designed according to the MSCML standard. Notifications provide information on the

number of active participants and their details.

The notifications are sent unsolicited at specific intervals requested by the application and

only when a change in the number of active conference speakers occurs. If a change in the

speakers list occurs, the server issues an INVITE to the specific SIP UA, and then transfers

the call to the UA.

Event notifications are sent in SIP INFO messages, as shown in the example below of XML

Response Generated for ASN:

<?xml version="1.0" encoding="utf-8"?>

</activetalkers>

</conference>

</notification>

</MediaServerControl>