Section: 5.2.1.2 Transfer of CDRs via Ga
Content: Upon receiving a charging event, the CDF uses the event to create/open a CDR (both event and session based charging), or to add information to an existing open CDR. As there is a 1:1 mapping between charging events and CDRs in event based charging, CDRs are created promptly after receiving and processing the event, and are then ready for transfer on to the CGF via the Ga reference point. In session based charging, a CDR is opened when the initial charging event, specifying the start of a user session, is received. Information is added to the CDR upon receiving interim charging events. The CDR may be closed due to a number of reasons configured on the CDF or dependent on implementation, including but not limited to: - time limit; - volume limit; - limit of change of charging conditions; - end of user session, e.g. reception of the final charging event describing the session termination; - limits (e.g. memory size) imposed by implementation. The CDR generation could be suppressed to limit the number of CDRs based on operator configuration. When a CDR is closed and the session is still active, a subsequent CDR is opened. Hence multiple "partial CDRs" may be needed to completely describe the session. This implies that opening and closure of CDRs may occur completely asynchronously to the reception of the charging events. The size of partial CDRs could be optionally reduced by allowing a reduced format for partial CDRs, implying that some information can be eliminated rather than repeated in all the partial CDRs. This means that only changes from one CDR to the next, in addition to mandatory information, is reported. All the missing information can be reconstructed from fields in previous partial CDRs. For example, if location information is captured in CDRs but the user did not change location, the corresponding partial CDR would not include any location information. Therefore, two formats are considered for Partial CDRs: - a Fully Qualified Partial CDR that contains the complete set of CDR Fields, and - a Reduced Partial CDR that contains all the Mandatory fields (M) and ONLY the changes that occurred in any other field relative to the previous partial CDR. The first CDR generated when a session is opened shall be a Fully Qualified Partial CDR. Subsequent partial CDRs may be Reduced Partial CDRs. Thus, the convention is that when any non-mandatory field is missing from a Reduced Partial CDR, it should be interpreted that the same field as in the previous partial CDR could be used. Refer to clause 5.4 for the definition of "mandatory" and other CDR field categories. All CDFs and CGFs from all vendors shall be able to generate or receive Fully Qualified Partial CDRs. Generation and reception of Reduced Partial CDRs on the Ga interface is optional. However, if Reduced Partial CDRs are transmitted on the Ga interface they must comply with the rules specified in this clause. If the CDFs are generating Reduced Partial CDRs on the Ga interface, the CGF must be able to convert the CDRs into Fully Qualified Partial CDRs. However, if according to operator choice, the BD can support Reduced Partial CDRs, no conversion to the Fully Qualified Partial CDR format is required. The possible charging configurations that can be supported on both the Ga and the Bx interfaces are illustrated in figure 5.2.1.2.1. Configuration a) is the default arrangement that MUST be supported by all systems. The other configurations are optional and may be supported IN ADDITION to configuration a). Configuration b) illustrates the case where the CGF is converting Reduced to Fully Qualified Partial CDRs. Configuration c) depicts the case were Reduced Partial CDRs can be received in the BD and no conversion is needed. Figure 5.2.1.2.1: Possible Configurations of Ga and Bx CDR Formats When a CDR is closed, it is immediately transferred to the CGF. The exact timing may be determined by configuration parameters of the protocol used on The CDF shall be capable of receiving and processing charging events and generating and forwarding the resulting CDRs in near real-time. Details on the protocol application for the open Ga interface can be found in TS 32.295[ Telecommunication management; Charging management; Charging Data Record (CDR) transfer ]  [54]. The semantics and formal description of the CDR parameters are specified in TS 32.298[ Telecommunication management; Charging management; Charging Data Record (CDR) parameter description ]  [51].