Section: 4.4.2.1 Ro
Content: The Ro reference point supports interaction between a CTF and an OCF. The following information may flow across this reference point: - Charging events for online charging from the CTF to the OCF. - Receive Acknowledgements for these charging events from the OCF to the CTF. The acknowledgement grants or rejects the network resource usage requested in the charging event, according to the decision taken by the OCS. The protocol(s) crossing this reference point shall support the following capabilities: - Real-time transactions; - Stateless mode ("event based charging") and statefull mode ("session based charging") of operation; NOTE: For "event based charging", the protocol may be stateless, however Internal implementation of the CTF and OCF may be stateful across the different charging events. - Provide its own reliability mechanisms, e.g. retransmission of charging events, to run also on unreliable transport. In addition, the protocol should support changeover to a secondary destination (alternate OCF(s)) in case of the primary OCF not being reachable. This interface application is defined in TS 32.299[ Telecommunication management; Charging management; Diameter charging applications ]  [50]. The information contained in the charging events and the relevant chargeable events are specific to the domain / subsystem / service and are detailed in the respective middle tier TSs.