The threshold
identifies when the reauthorization must take place.
Online Charging Procedures and Message Flow There are several messages needed for
online charging as already outlined, Credit-control-request and Credit-control-answer
being the primary messages. When a subscriber requests service, the serving node
sends a Credit-control-request to the OCS. The OCS bears the responsibility of rating
the event (through the rating function) and then verifying the account balance of the
subscriber (the account balance management function). If there is no balance in the
account, of course the event is denied and the OCS sends the appropriate message back
to the CTF.
If there is a balance in the account, the amount needed for the event is established
through the rating function. The amount is then sent to the ABMF to be debited from
the account.
198 Chapter 7
Event sessions are handled somewhat differently, since there is no time base involved.
For example, a subscriber elects to subscribe to a weather alert service from
their local operator. Their device uses the SUBSCRIBE method for establishing the
subscription to the service in the SIP domain.
The subscription request is sent to the application server (AS) providing the weather
service after the event has been rated by the rating function. The AS then sends a
DIAMETER Credit-control-request message to the OCS to determine how to rate for
the event.
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