Figure13.5 SIP NOTIFY flowSIP event packages have been proposed and developed for numerous appli-
cations, some of which have been reported in IETF Internet drafts, though not
all of them have made it to the standards level. As seen from the following list
(which is not complete), event-based SIP communications constitute a signifi-
cant area for product innovation. We believe many such innovations are likely
to proliferate in IP communications based on SIP. SIP event packages include
the following:
■■ Automatic updates of Internet Media Guides [3]
■■ Registrations of SIP UA with servers to change or enforce policy [4]
■■ Notifications about the dialog state of INVITEinitiated dialogs [5]
■■ Message waiting alerts [6]
■■ Conference state (such as reporting the attendance and speaker
name) [7]
■■ Push-to-talk over cellular networks [8]
■■ Key events for buttons, feature keys, and so on [9]
■■ Key press stimulus for monitoring DTMF signals using XML
documents [10]
■■ Location events using location filters [11]
■■ Remote device configuration and status information [12]
■■ Call control events happening in the PSTN [13]SubscriberSUBSCRIBE200NOTIFY200NOTIFYRequest state subscriptionAcknowledge subscriptionReturn current state infoReturn new state info
200Notifier230 Chapter 13