The Offline Charging System (OFCS) is a grouping of charging functions used for Offline Charging. It collects and
processes charging events from one or more CTFs, and it generates CDRs for subsequent offline downstream billing
The Online Charging System (OCS) performs online credit control functions.
The OCS may trigger the PCEF to initiate an IP-CAN bearer service termination at any point in time.
There may be several OCSs in a PLMN.