7.3.1 GPRS Attach Procedure

23.1193GPPGateway Location Register (GLR)Release 17Stage 2TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

Three cases are described in this section:

– The new SGSN is within a VPLMN served by the GLR. The old SGSN interfaces to the HLR directly.

– The new SGSN and old SGSN are within a VPLMN served by the same GLR.

– The new SGSN is within a VPLMN served by the GLR. The old SGSN is within a different VPLMN served by the GLR.

– The new SGSN interfaces to the HLR directly. The old SGSN is within a VPLMN served by the GLR.

7.3.1.1 New SGSN served by GLR, old SGSN served by HLR

Figure 7.3/1: GPRS Attach Procedure involving GLR (new SGSN is under the GLR. Old SGSN interfaces the HLR directly)

1) to 5) These steps are the same as the steps not involving GLR. See TS 23.060 [6].

6) If the SGSN number has changed since the GPRS detach, or if it is the very first attach, then the SGSN informs the HLR via GLR:

a) The SGSN sends an Update Location (SGSN Number, SGSN Address, and IMSI) to the GLR. Then the GLR sends an Update Location (GLR Number, IM-GSN address, IMSI) to the HLR, if the GLR does have the IMSI record. Note that, GLR Number and IM-GSN address should respectively be set in SGSN Number parameter and SGSN address parameters.

b) The HLR sends Cancel Location (IMSI, Cancellation Type) to the old SGSN with Cancellation Type set to Update Procedure.

c) The old SGSN acknowledges with Cancel Location Ack (IMSI). If there are any ongoing procedures for that MS, the old SGSN shall wait until these procedures are finished before removing the MM and PDP contexts.

d) The HLR sends Insert Subscriber Data (IMSI, GPRS subscription data) to the GLR. The GLR sends Insert Subscriber Data (IMSI, GPRS subscription data) to the new SGSN.

e) The new SGSN validates the MS’s presence in the (new) RA. If due to regional subscription restrictions the MS is not allowed to attach in the RA, the SGSN rejects the Attach Request with an appropriate cause, and may return an Insert Subscriber Data Ack (IMSI, SGSN Area Restricted) message to the GLR. Then, the GLR set the SGSN area restricted flag "true" and transfers the SGSN area restricted indication to the HLR within the Insert Subscriber Data Ack message. Note that some modification at the application level might be needed here to maintain compatibility with the message format of (6d). If subscription checking fails for other reasons, the SGSN rejects the Attach Request with an appropriate cause and returns an Insert Subscriber Data Ack (IMSI, Cause) message to the GLR, which the GLR transfers to the HLR within the Insert Subscriber Data Ack message. Note that some modification at the application level might be needed here to maintain compatibility with the message format of (6d). If all checks are successful then the SGSN constructs an MM context for the MS and returns an Insert Subscriber Data Ack (IMSI) message to the GLR, which the GLR transfers to the HLR.

f) The HLR acknowledges the Update Location message by sending an Update Location Ack to the GLR and the GLR send it to the SGSN after the cancelling of old MM context and insertion of new MM context are finished. If the Update Location is rejected by the HLR, the SGSN rejects the Attach Request from the MS with an appropriate cause.

8) and 9) These steps are the same as the steps not involving GLR. See TS 23.060 [6].

If the Attach Request cannot be accepted, the SGSN returns an Attach Reject (IMSI, Cause) message to the MS.

7.3.1.2 New SGSN and old SGSN served by the same GLR

Figure 7.3/2: GPRS Attach Procedure involving GLR (new SGSN and old SGSN
are under in the same GLR)

1) to 5) These steps are the same as the steps not involving GLR. See TS 23.060 [6].

6) If the SGSN number has changed since the GPRS detach, or if it is the very first attach, then the SGSN informs the GLR:

a) The SGSN sends an Update Location (SGSN Number, SGSN Address, and IMSI) to the GLR. If the GLR has the IMSI record, the GLR does not send an Update Location message to the HLR.

b) The GLR sends Cancel Location (IMSI, Cancellation Type) to the old SGSN with Cancellation Type set to Update Procedure.

d) The GLR sends Insert Subscriber Data (IMSI, GPRS subscription data) to the new SGSN.

e) The new SGSN validates the MS’s presence in the (new) RA. If due to regional subscription restrictions the MS is not allowed to attach in the RA, the SGSN rejects the Attach Request with an appropriate cause, and may return an Insert Subscriber Data Ack (IMSI, SGSN Area Restricted) message to the GLR. If the SGSN area restricted flag is set "false" in the GLR, the GLR sets the lag "true" and sends an Update Location (GLR Number, IM-GSN address, IMSI) to the HLR. Clause 7.5 describes the detail procedure. Note that, GLR Number and IM-GSN address should respectively be set in SGSN Number parameter and SGSN address parameters. If subscription checking fails for other reasons, the SGSN rejects the Attach Request with an appropriate cause and returns an Insert Subscriber Data Ack (IMSI, Cause) message to the GLR. If all checks are successful then the SGSN constructs an MM context for the MS and returns an Insert Subscriber Data Ack (IMSI) message to the GLR.

f) The GLR acknowledges the Update Location message by sending an Update Location Ack to the SGSN after the cancelling of old MM context and insertion of new MM context are finished. If the Update Location is rejected by the GLR, the SGSN rejects the Attach Request from the MS with an appropriate cause.

8) and 9) These steps are the same as the steps not involving GLR. See TS 23.060 [6].

If the Attach Request cannot be accepted, the SGSN returns an Attach Reject (IMSI, Cause) message to the MS.

7.3.1.3 New SGSN served by the GLR, and old SGSN served by the other GLR

Figure 7.3/3: GPRS Attach Procedure involving GLR (new SGSN and old SGSN are under in the different GLR)

1) to 5) These steps are the same as the steps not involving GLR. See TS 23.060 [6].

6) If the SGSN number has changed since the GPRS detach, or if it is the very first attach, then the SGSN informs the HLR via GLR:

a) The SGSN sends an Update Location (SGSN Number, SGSN Address, and IMSI) to the GLR. Then the GLR sends an Update Location (GLR Number, IM-GSN address, IMSI) to the HLR if the GLR does not have the IMSI record. Note that, GLR Number and IM-GSN address should respectively be set in SGSN Number parameter and SGSN address parameters in the actual MAP operation.

b) The HLR sends Cancel Location (IMSI, Cancellation Type) to the old GLR with Cancellation Type set to Update Procedure. Then the GLR sends Cancel Location (IMSI, Cancellation Type) to the old SGSN with Cancellation Type set to Update Procedure.

d) The HLR sends Insert Subscriber Data (IMSI, GPRS subscription data) to the GLR. The GLR sends Insert Subscriber Data (IMSI, GPRS subscription data) to the new SGSN.

e) The new SGSN validates the MS’s presence in the (new) RA. If due to regional subscription restrictions the MS is not allowed to attach in the RA, the SGSN rejects the Attach Request with an appropriate cause, and may return an Insert Subscriber Data Ack (IMSI, SGSN Area Restricted) message to the GLR. The GLR sets the SGSN area restricted flag "true" and transfers the SGSN area restricted indication to the HLR within the Insert Subscriber Data Ack message. Note that some modification at the application level might be needed here to maintain compatibility with the message format of (6d). If subscription checking fails for other reasons, the SGSN rejects the Attach Request with an appropriate cause and returns an Insert Subscriber Data Ack (IMSI, Cause) message to the GLR, which the GLR transfers to the HLR within the Insert Subscriber Data Ack message. Note that some modification at the application level might be needed here to maintain compatibility with the message format of (6d). If all checks are successful then the SGSN constructs an MM context for the MS and returns an Insert Subscriber Data Ack (IMSI) message to the GLR, which the GLR transfers to the HLR.

8) and 9) These steps are the same as the steps not involving GLR. See TS 23.060 [6].

If the Attach Request cannot be accepted, the SGSN returns an Attach Reject (IMSI, Cause) message to the MS.

7.3.1.4 New SGSN served by HLR, old SGSN served by GLR

Figure 7.3/4: GPRS Attach Procedure involving GLR (new SGSN interfaces the HLR directly. Old SGSN is under the GLR)

1) to 5) These steps are the same as the steps not involving GLR. See TS 23.060 [6].

6) If the SGSN number has changed since the GPRS detach, or if it is the very first attach, then the SGSN informs the HLR:

a) The SGSN sends an Update Location (SGSN Number, SGSN Address, and IMSI) to the HLR.

b) The HLR sends Cancel Location (IMSI, Cancellation Type) to the old GLR, then the GLR sends Cancel Location (IMSI, Cancellation Type) to the old SGSN with Cancellation Type set to Update Procedure.

c) The old SGSN acknowledges with Cancel Location Ack (IMSI) via the GLR. If there are any ongoing procedures for that MS, the old SGSN shall wait until these procedures are finished before removing the MM and PDP contexts.

d) The HLR sends Insert Subscriber Data (IMSI, GPRS subscription data) to the new SGSN.

f) The HLR acknowledges the Update Location message by sending an Update Location Ack to the SGSN after the cancelling of old MM context and insertion of new MM context are finished. If the Update Location is rejected by the HLR, the SGSN rejects the Attach Request from the MS with an appropriate cause.

8) and 9) These steps are the same as the steps not involving GLR. See TS 23.060 [6].

If the Attach Request cannot be accepted, the SGSN returns an Attach Reject (IMSI, Cause) message to the MS.

7.3.1.5 Functional requirements of GLR

7.3.1.5.1 Process Update_GPRS_Location_GLR

Figure 7.3/5 shows SDL chart for Process Update_GPRS_Location_GLR.

Sheet1: the test "HLR update required?" takes the "yes" exit the GLR checks some flags to perform the "Location Updating Screening Function (see to clause 7.1.6)" and if it is needed to update location information to the HLR.

Sheet2: after the GLR sends an Update GPRS Location message to the HLR, the GLR receives the response with:

– an Insert Subscriber Data message, handled by the procedure Insert_Subscriber_Data_GLR shown in clause 7.2.1;

– an Update GPRS Location ack message. If the GLR receives this message, this indicates that updating has been successfully completed. The GLR sets the "(Location and Subscriber information) LSIC by HLR" indicator to "Confirmed". The GLR send an Update GPRS Location ack message to the SGSN;

– an Update GPRS Location negative response message. If the GLR receives this message, this indicates that updating has been unsuccessfully completed. The GLR sets the "(Location and Subscriber information) LSIC by HLR" indicator to "False". The GLR sends an Update GPRS Location negative to the SGSN.

Sheet3: process Cancel_GPRS_Location_Initiated_GLR is specified in clause 7.3.1.5.4.

Figure7.3/5(1): Process Update_GPRS_Location_GLR

Figure7.3/5(2): Process Update_GPRS_Location_GLR

Figure7.3/5(3): Process Update_GPRS_Location_GLR

Figure7.3/5(4): Process Update_GPRS_Location_GLR

Figure7.3/5(5): Process Update_GPRS_Location_GLR

Figure7.3/5(6): Process Update_GPRS_Location_GLR

Figure7.3/5(7): Process Update_GPRS_Location_GLR

7.3.1.5.2 Process Subscriber_Present_GPRS_GLR

Figure 7.3/6 shows SDL chart for Process Subscriber_Present_GPRS_GLR.

Figure7.3/6: Process Subscriber_Present_GPRS_GLR

7.3.1.5.3 Procedure Insert_Subscriber_Data_GPRS_Initiated_GLR

Figure 7.3/7 shows SDL chart for Procedure Insert_Subscriber_Data_GPRS_Initiated_GLR. This procedure is initiated if HLR update is not required.

Figure7.3/7: Procedure Insert_Subscriber_Data_GPRS_Initiated_GLR

7.3.1.5.4 Process Cancel_GPRS_Location_Initiated_GLR

Figure 7.3/8 shows SDL chart for Process Cancel_GPRS_Location_Initiated_GLR. This procedure is initiated if HLR update is not required.

Figure7.3/8: Process Cancel_GPRS_Location_Initiated_GLR