The Wf reference point is located between 3GPP AAA Server/Proxy and 3GPP Offline Charging System. The prime
purpose of the protocols crossing this reference point is to transport/forward offline charging information towards 3GPP
operator's Offline Charging System located in the visited network or home network where the subscriber is residing.
The functionality of this reference point is to provide information needed by
the WAG to perform policy enforcement functions for authorised users and to transport per-tunnel based charging
information from the WAG to the AAA Proxy in roaming scenarios.
This is the reference point between the PDG and a packet data network. It may be an operator external public or private packet data network or an intra operator packet data network, e.g. for provision of IMS services.
The Wo reference point is used by a 3GPP AAA Server to communicate with 3GPP Online Charging System (OCS).
The prime purpose of the protocol(s) crossing this reference point is to transport online charging related information so
as to perform credit control for the online charged subscriber.
The Wy reference point is used by a PDG to communicate with an Online Charging System (OCS). The purpose of the
protocol(s) crossing this reference point is to transport online charging related information about WLAN 3GPP IP
Access so as to perform credit control for the online charged subscriber.
The Wz reference point is used by a PDG to communicate with an Offline Charging System. The purpose of the
protocol(s) crossing this reference point is to transport offline charging related information about WLAN 3GPP IP
Access.