The OCS sends the Credit-control-answer back to the AS so that the service
can begin. The ABMF function debits the subscriber??™s account immediately.
If this is a session-based event, then the amount needed is not yet known. This may
then require ???unit reservation.??? This is where the exact usage may not be known so a
reserve amount is provided.
When the reserve amount is depleted, the serving node sends another Creditcontrol-
request, or a Re-auth-request to the OCS, which is then rated, and another reserve
amount allocated. If the session is completed and there is excess in the reserved
amount allocated, then the excess can be credited back to the subscriber account.
The OCS is ultimately responsible for approving a session based on available credit
or denying service. There are provisions that would allow the OCS to grant services
even if an account were depleted, leaving the decision process to an operator??™s specific
implementation. This means that there is no absolute rule that says when an account
is depleted, service will be denied.
The network element itself has the ultimate responsibility to manage the session.
Given the number of units allowed from the OCS, the network element is responsible
for terminating a call once the units have been depleted (the account balance then is
depleted). The network element can then launch another charging event to the OCS for
additional units for the call to continue.
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