HP-UX C SIP Stack Programmer's Guide (Novembery 2007)

Event Notification 229
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EVENT NOTIFICATION
INTRODUCTION The Event Notification feature, as defined in RFC 3265, provides an extensible
framework by which SIP nodes can request notification from remote nodes
indicating that certain events have occurred.
The concept behind the Event Notification feature is that entities in the network
can subscribe to several resources and/or call states. Each resource and/or call
state updates the entity subscribed to it with the states of the specific event.
DEFINITIONS Notifier
A notifier is an application agent which generates NOTIFY requests for the
purpose of notifying subscribers of the state of a resource. Notifiers typically
accept SUBSCRIBE requests to create subscriptions.
Subscriber
A subscriber is an application agent which receives NOTIFY requests from
notifiers—these NOTIFY requests contain information about the state of a
resource in which the subscriber is interested. Subscribers typically generate
SUBSCRIBE requests and send them to notifiers to create subscriptions.
Subscription
A subscription is a set of application states associated with a dialog. A
subscription includes a pointer to the associated dialog and the event of the
subscription. By definition, subscriptions exist in both a subscriber and a
notifier.