The VLR is the location and management data base for the MSs roaming in the area controlled by the associated
MSC(s). Whenever the MSC needs data related to a given MS currently located in its area, it interrogates the VLR.
When a MS initiates a location updating procedure with an MSC, the MSC informs its VLR which stores the relevant
information in its tables. This procedure occurs whenever a mobile roams to another location area. Also, for instance
when a subscriber activates a specific supplementary service or modifies some data attached to a service, the MSC
transfers (via the VLR) the request to the HLR, which stores these modifications and updates the VLR if required.
However, this interface is not fully operational specified. It is strongly recommended not to implement the B-interface
as an external interface.
By definition, dealing with CDR files only implies that Bx is solely related to offline charging.
The CGF in each network domain, service or subsystem is relevant for the network side of
the Bx reference point and is connected with the Billing Domain that forms the receiving end of the Bx reference point.
Further details of the Billing Domain, i.e. beyond terminating Bx, are outside the scope of 3GPP standardization.
Note that the OCS can also generate CDRs and transfer them to the BD across the Bo reference point.
Furthermore the GSM SCF, defined in CAMEL, can also generate CDRs and transfer them to the BD across the Bs