VoiceXML servers also have some telephony features, such as call transfer
and disconnect, but these may not always be necessary in the presence of a ser-
vice controller as discussed here. The following example reproduces a sample
dialog from the VoiceXML specification [5] that shows the power of IVRs using
VoiceXML:
Computer: Welcome to the weather information service. What state?
Human: Help
Computer Please speak the state for which you want the weather.
Human: Georgia
Computer What City?
Human: Tblisi
Computer I do not understand what you said. What city?
Human: Macon
Computer: The conditions in Macon, Georgia are sunny and clear at 11
AM...Scheduled Conference Service
A large variety of conference types are possible on the Internet, from sponta-
neous initiated conferences using presence, to telecom-type scheduled confer-
ences. However, for most types of network-based conferences, a mixing voice
bridge is necessary, such as discussed in Chapter 14, “SIP Conferencing.”
Therefore, it makes sense to separate the conference-scheduling servers from
the voice-mixing bridge, since they are so very different in functionality and
technology. Figure 19.7 shows an example of the call flow for a scheduled con-
ference using separate scheduling and mixing servers. In this example, we
assume that the scheduling server is also the controller.
The conference is scheduled and set up on the Web server, which, in turn,
informs the scheduler using an HTTPPOSTmessage (1). The controller con-
firms the conference is possible and will be scheduled in the 200 OKmessage
(2) to the Web server. E-mail or some other means can also be used to inform
the users of the scheduled conference.
At the scheduled time, the controller will connect the users successively to
the voice-mixing bridge. Only two users, A and B, are shown here for simplic-
ity, since all additional users would have the same call flows for call setup with
the conference bridge. Note that an alternative service would be the controller
could call the participants A and B and use third-party call control to connect
them to the mixing bridge.
SIP Component Services 335