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

230 HP-UX C SIP Stack Programmer’s Guide
Typical Message Flow
TYPICAL MESSAGE
F
LOW
Figure 12-1 demonstrates a typical flow of messages in a subscription.
Figure 12-1 Message Flow
1.
In order to subscribe to a resource or call sate, the subscriber
sends a SUBSCRIBE request to the notifier. The SUBSCRIBE
Subscriber
Notifier
1.SUBSCRIBE
Expires:100
2. 200
Expires:80
3. Notify (active)
200
6. Notify (active)
200
5. SUBSCRIBE (refresh)
Expires:50
200
Expires:50
7. SUBSCRIBE (unsubscribe)
Expires:0
200
8. Notify (terminated)
200
4. Notify (active)
200
SUBSCRIBE
Event
Notification
REFRESH
UNSUBSCRIBE