19.1.4 Purge MS

09.023GPPMobile Application Part (MAP) specificationTS

19.1.4.1 General

When the VLR or the SGSN receives an indication on the O&M interface that the MS record is to be purged (either because of administrative action or because the MS has been inactive for an extended period), this procedure invokes the MAP_PURGE_MS service described in subclause 8.1.6 to request the HLR to set the "MS purged for non-GPRS" or the “MS purged for GPRS” flag for the MS so that any request for routing information for a mobile terminated call or a mobile terminated short message will be treated as if the MS is not reachable. The message flows are shown in figures 19.1.4/1and 19.1.4/5.

It is optional for the network operator to delete MS records from the VLR or from the SGSN, but if the option is used the VLR or the SGSN shall notify the HLR when a record has been deleted.

The O&M process in the VLR or in the SGSN must ensure that during the MS purging procedure any other attempt to access the MS record is blocked, to maintain consistency of data.

+—–+ D +—–+
ª VLR +——–|———–ª HLR ª
+—–+ +—–+
ª ª ßß
ª MAP_PURGE_MS ª ßß
ª————————->ª ßß
ª ª ßß
ª MAP_PURGE_MS_ack ª ßß
ª<————————-ª ßß
ª ª ßß
ª ª ß

Figure 19.1.4/1: MAP-D Interface and services for MAP_PURGE_MS

+—–+ Gr +—–+
ª SGSN+——–|———–ª HLR ª
+—–+ +—–+
ª ª ßß
ª MAP_PURGE_MS ª ßß
ª————————->ª ßß
ª ª ßß
ª MAP_PURGE_MS_ack ª ßß
ª<————————-ª ßß
ª ª ßß
ª ª ß

Figure 19.1.4/5: Gr Interface and services for MAP_PURGE_MS

19.1.4.2 Detailed procedure in the VLR

When the VLR receives an indication from O&M that an MS record is to be purged, it invokes the MAP_PURGE_MS service (see figure 19.1.4/2).

The VLR opens the dialogue to the HLR with a MAP_OPEN request containing no user specific parameters. The MAP_PURGE_MS request contains the IMSI of the MS which is to be purged and the VLR number.

The VLR then waits for the MAP_OPEN confirmation (see macro Receive_Open_Cnf, subclause 25.1), indicating one of:

– rejection of the dialogue (process terminates);

– reversion to version one (process terminates);

– dialogue acceptance.

If the HLR accepts the dialogue it returns a MAP_PURGE_MS confirmation, containing no parameter, indicating successful outcome of the procedure.

If a MAP_PURGE_MS confirmation containing a provider error, data error or user error, or a MAP_P_ABORT, MAP_NOTICE or premature MAP_CLOSE indication, has been received, the failure is reported to the O&M interface. Successful outcome of the procedure leads to deletion of the subscriber data and freezing of the TMSI if so requested by the HLR, and is reported to the O&M interface.

19.1.4.3 Detailed procedure in the HLR

Opening of the dialogue is described in the macro Receive_Open_Ind in subclause 25.1. The possible outcomes are:

– termination of the procedure if the AC indicates a version 1 dialogue, as this procedure is not defined for version 1;

– termination of the procedure if there is an error;

– dialogue acceptance, in which case the procedure is as described below.

If the HLR receives a MAP_NOTICE indication, it terminates the dialogue by sending a MAP_CLOSE request.

If the HLR receives a MAP_PURGE_MS indication (see figure 19.1.4/3), it first checks the indication data (macro Check_Indication, see subclause 25.2). If there is a parameter error the HLR terminates the dialogue by sending an appropriate error in the MAP_PURGE_MS response in a MAP_CLOSE request . If there is no parameter error the HLR then checks whether the subscriber is known.

– if the subscriber is unknown, the HLR reports an error to the O&M interface, the error Unknown Subscriber is returned in the MAP_PURGE_MS response and the dialogue is terminated by sending a MAP_CLOSE request ;

– if the subscriber is known, the HLR checks whether the purging notification came from the VLR or SGSN where the MS was last registered:

– if the received VLR number and the stored VLR number match, the HLR sets the "MS purged for non-GPRS" flag for the subscriber and sends a MAP_PURGE_MS response containing a freeze TMSI indicator to indicate successful outcome;

– if the received VLR number and the stored VLR number do not match, the HLR sends a MAP_PURGE_MS response containing an empty result to indicate successful outcome. Since the MS is known by the HLR to be in a different VLR area, it is not appropriate to block mobile terminated calls or short messages to the MS, but the VLR which initiated the purging procedure can safely purge its record for the MS without freezing the TMSI.

– if the received SGSN number and the stored SGSN number match, the HLR sets the "MS purged for GPRS" flag for the subscriber and sends a MAP_PURGE_MS response containing a freeze P-TMSI indicator to indicate successful outcome;

– if the received SGSN number and the stored SGSN number do not match, the HLR sends a MAP_PURGE_MS response containing an empty result to indicate successful outcome. Since the MS is known by the HLR to be in a different SGSN area, it is not appropriate to block short messages to the MS, but the SGSN which initiated the purging procedure can safely purge its record for the MS without freezing the P-TMSI.

In either cases of successful termination the HLR terminates the dialogue by sending a MAP_CLOSE request.

19.1.4.4 Detailed procedure in the SGSN

When the SGSN receives an indication from O&M that an MS record is to be purged, it invokes the MAP_PURGE_MS service (see figure 19.1.4/4).

The SGSN opens the dialogue to the HLR with a MAP_OPEN request containing no user specific parameters. The MAP_PURGE_MS request contains the IMSI of the MS which is to be purged and the SGSN number.

The SGSN then waits for the MAP_OPEN confirmation (see macro Receive_Open_Cnf, subclause 25.1), indicating one of:

– rejection of the dialogue (process terminates);

– reversion to Vr (process terminates);

– dialogue acceptance.

If the HLR accepts the dialogue it returns a MAP_PURGE_MS confirmation, containing no parameter, indicating successful outcome of the procedure.

If a MAP_PURGE_MS confirmation containing a provider error, data error or user error, or a MAP_P_ABORT, MAP_NOTICE or premature MAP_CLOSE indication, has been received, the failure is reported to the O&M interface. Successful outcome of the procedure leads to deletion of the subscriber data and freezing of the P-TMSI if so requested by the HLR, and is reported to the O&M interface.

Figure 19.1.4/2: Process Purge_MS_VLR

Figure 19.1.4/3: Process Purge_MS_HLR

Figure 19.1.4/4: Process Purge_MS_SGSN