7.3.6 PDP Context Activation Procedure

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

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

7.3.6.1 Successful Network-Requested PDP Context Activation Procedure with GLR

The Successful Network-Requested PDP Context Activation procedure is illustrated in Figure 7.3/15. Each step is explained in the following list.

Figure 7.3/15: Successful Network-Requested PDP Context Activation Procedure

1) When receiving a PDP PDU the GGSN determines if the Network-Requested PDP Context Activation procedure has to be initiated. The GGSN may store subsequent PDUs received for the same PDP address.

2) The GGSN may send a Send Routeing Information for GPRS (IMSI) message to the HLR. If the HLR determines that the request can be served, it returns a Send Routeing Information for GPRS Ack (IMSI, SGSN Address, Mobile Station Not Reachable Reason) message to the GGSN. The SGSN Address parameter includes actually the value of the IM-GSN Address. The Mobile Station Not Reachable Reason parameter is included if the MNRG flag is set in the HLR. The Mobile Station Not Reachable Reason parameter indicates the reason for the setting of the MNRG flag as stored in the MNRR record (see TS 23.040 [5]). If the MNRR record indicates a reason other than ‘No Paging Response’, the HLR shall include the GGSN number in the GGSN‑list of the subscriber.

– If the HLR determines that the request cannot be served (e.g., IMSI unknown in HLR), the HLR shall send a Send Routeing Information for GPRS Ack (IMSI, MAP Error Cause) message. Map Error Cause indicates the reason for the negative response.

3) If the SGSN address is present and either Mobile Station Not Reachable Reason is not present or Mobile Station Not Reachable Reason indicates ‘No Paging Response’, the GGSN shall send a PDU Notification Request (IMSI, PDP Type, PDP Address) message to the IM-GSN indicated by the HLR. Otherwise, the GGSN shall set the MNRG flag for that MS. The IM-GSN sends a Send Routeing Information for GPRS (IMSI) message to the GLR. If the GLR determines that the request can be served, it returns a Send Routeing Information for GPRS Ack (IMSI, SGSN Address, Mobile Station Not Reachable Reason) message to the IM-GSN. If the SGSN address is present and either Mobile Station Not Reachable Reason is not present or Mobile Station Not Reachable Reason indicates ‘No Paging Response’, the IM-GSN shall send a PDU Notification Request (IMSI, PDP Type, PDP Address) message to the SGSN indicated by the GLR. The SGSN returns a PDU Notification Response (Cause) message to the GGSN via the IM-GSN in order to acknowledge that it shall request the MS to activate the PDP context indicated with PDP Address.

4) The SGSN sends a Request PDP Context Activation (TI, PDP Type, and PDP Address) message to request the MS to activate the indicated PDP context.

5) The PDP context is activated with the PDP Context Activation procedure (see clause "PDP Context Activation Procedure" in 3G TS 23.060 [6]).

7.3.6.2 Unsuccessful Network-Requested PDP Context Activation Procedure with GLR

If the PDP context requested by the GGSN cannot be established, the SGSN sends a PDU Notification Response (Cause) or a PDU Notification Reject Request (IMSI, PDP Type, PDP Address, Cause) message to the GGSN depending on whether the context activation fails before or after the SGSN has sent a Request PDP Context Activation message to the MS. Cause indicates the reason why the PDP context could not be established:

– ‘IMSI Not Known’. The SGSN has no MM context for that IMSI (Cause in PDU Notification Response).

– ‘MS GPRS Detached’. The MM state of the MS is IDLE (Cause in PDU Notification Response).

– ‘MS Not GPRS Responding’. The MS is GPRS-attached to the SGSN but the MS does not respond. This may be due to:

– the lack of a response to a GPRS Paging Request;

– an Abnormal RLC condition, or

– no Activate PDP Context Request message received within a certain time after the Request PDP Context Activation message was delivered to the MS (Cause in PDU Notification Reject Request).

– ‘MS Refuses’. The MS refuses explicitly the network-requested PDP context (Cause in PDU Notification Reject Request).

When receiving the PDU Notification Response or the PDU Notification Reject Request message the GGSN may reject or discard the PDP PDU depending on the PDP type.

After an unsuccessful Network-Requested PDP Context Activation procedure the network may perform some actions to prevent unnecessary enquires to the HLR. The actions taken depend on the cause of the delivery failure.

– If the MS is not reachable or if the MS refuses the PDP PDU (Cause value ‘MS Not GPRS Responding’ or ‘MS Refuses’), then the SGSN shall not change the setting of MNRG for this MS. The GGSN may refuse any PDP PDU for that PDP address during a certain period. The GGSN may store the SGSN address during a certain period and send subsequent PDU Notification Request messages to that SGSN via IM-GSN.

– If the MS is GPRS-detached or if the IMSI is not known in the SGSN (Cause value ‘MS GPRS Detached’ or ‘IMSI Not Known’), then the SGSN, the GGSN, and the HLR may perform the Protection and Mobile User Activity procedures.

The Protection procedure is illustrated in Figure 7.3/16. Each step is explained in the following list.

Figure 7.3/16: Protection Procedure

1) If the MM context of the mobile is IDLE or if the SGSN has no information about that user, the SGSN returns a PDU Notification Response (Cause) message to the GGSN via IM-GSN with Cause equal to ‘MS GPRS Detached’ or ‘IMSI Not Known’, otherwise the Cause shall be ‘Activation Proceeds’. If the Cause is ‘MS GPRS Detached’ or ‘IMSI Not Known’ and if the SGSN has an MM context for that user, the SGSN sets MNRG to indicate the need to report to the HLR when the next contact with that MS is performed.

2) If the MS does not respond or refuses the activation request, the SGSN sends a PDU Notification Reject Request (IMSI, PDP Type, PDP Address, Cause) message to the GGSN via IM-GSN with Cause equal to ‘MS Not GPRS Responding’ or ‘MS Refuses’. The GGSN returns a PDU Notification Reject Response message to the SGSN via IM-GSN.

3) If Cause equals ‘IMSI Not Known’ the IM-GSN may send a Send Routeing Information for GPRS (IMSI) message to the GLR before sending the PDP Notification response to GGSN. The GLR returns a Send Routeing Information for GPRS Ack (IMSI, SGSN Address, and Cause) message to the IM-GSN indicating the address of the SGSN that currently serves the MS. If SGSN Address is different from the one previously stored by the IM-GSN, then steps 3, 4, and 5 in Figure 6 are followed.
If Cause equals ‘IMSI Not Known’ the GGSN may send a Send Routeing Information for GPRS (IMSI) message to the HLR. The HLR returns a Send Routeing Information for GPRS Ack (IMSI, SGSN Address, Cause) message to the GGSN (Note that the SGSN Address parameter includes actually the value of the IM-GSN Address.) indicating the address of the IM-GSN that currently serves the MS. If IM-GSN Address is different from the one previously stored by the GGSN, then steps 3, 4, and 5 in Figure 6 are followed.

4) If SGSN Address is the same as the one previously stored in the IM-GSN or if the Cause value returned in step 1 equals ‘MS GPRS Detached’, then the IM-GSN sets MNRG for that PDP address and sends a Failure Report (IMSI) message to the GLR to request MNRG to be set in the GLR. The GLR sets (if not already set) MNRG for the IMSI. Note that GLR does not store IM-GSN address and IM-GSN address to report to when activity from that IMSI is detected, and IM-GSN forgets the SGSN address after receiving PDU notification response or sending PDU notification reject response.

If IM-GSN Address is the same as the one previously stored in the GGSN, or if the Cause value returned in step 1 equals ‘MS GPRS Detached’, then the GGSN sets MNRG for that PDP address and sends a Failure Report (IMSI, GGSN Number, GGSN Address) message to the HLR to request MNRG to be set in the HLR. The HLR sets (if not already set) MNRG for the IMSI and adds GGSN Number and GGSN Address to the list of GGSNs to report to when activity from that IMSI is detected. GGSN Number is either the number of the GGSN, or, if a protocol converting GSN is used as an intermediate node, the number of the protocol-converting GSN. GGSN Address is an optional parameter that shall be included if a protocol-converting GSN is used.

The Mobile User Activity procedure is illustrated in Figure 7.3/17. Each step is explained in the following list.

Figure 7.3/17: Mobile User Activity Procedure

1) The SGSN receives an indication that an MS is reachable, e.g., an Attach Request message from the MS.

2a) If the SGSN contains an MM context of the MS and MNRG for that MS is set, the SGSN shall send a Ready for SM (IMSI, MS Reachable) message to the GLR and clears MNRG for that MS. The GLR sends it without modification at the application level to HLR and clears MNRG for that MS.

2b) If the SGSN does not keep the MM context of the MS, the SGSN shall send an Update Location message (see clause "Attach Function") to the GLR. If the GLR does not keep the MM context of the MS, the SGSN shall send an Update Location message (see clause "Attach Function") to the HLR.

2c) If the GLR contains an MM context of the MS and MNRG for that MS is set, the SGSN shall send a Ready for SM (IMSI, MS Reachable) message to the HLR and clears MNRG for that MS.

3) When the HLR receives the Ready for SM message or the Update Location message for an MS that has MNRG set, it clears MNRG for that MS and sends a Note MS GPRS Present (IMSI, SGSN Address) message to all the GGSNs in the list of the subscriber. (The Ready for SM message also triggers the SMS alert procedure as described in clause "Unsuccessful Mobile-terminated SMS Transfer".) SGSN Address contains the address of the IM-GSN that currently serves the MS. Upon reception of Note MS Present, each GGSN shall clear MNRG.