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Content for  TS 23.060  Word version:  16.0.0

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9.2.2.2  Network-Requested PDP Context Activation ProcedureWord‑p. 245
The Network-Requested PDP Context Activation procedure allows the GGSN to initiate the activation of a PDP context. When receiving a PDP PDU the GGSN checks if a PDP context is established for that PDP address. If no PDP context has been previously established, the GGSN may try to deliver the PDP PDU by initiating the Network-Requested PDP Context Activation procedure. The criteria used by the GGSN to determine whether trying to deliver the PDP PDU to the MS may be based on subscription information are outside the scope of GPRS standardisation.
To support Network-Requested PDP Context Activation, the GGSN has to have static PDP information about the PDP address. To determine whether Network-Requested PDP Context Activation is supported for a PDP address, the GGSN checks if there is static PDP information for that PDP address.
Once these checks have been performed the GGSN may initiate the Network-Requested PDP Context Activation procedure.
The network operator may implement the following techniques to prevent unnecessary enquires to the HLR:
  • Implementation of the Mobile station Not Reachable for GPRS flag (MNRG) technique in GGSN, SGSN, and HLR (see clause "Unsuccessful Network-Requested PDP Context Activation Procedure").
  • The GGSN may reject or discard PDP PDUs after a previous unsuccessful delivery attempt. This systematic rejection of PDP PDUs would be performed during a certain time after the unsuccessful delivery.
  • The GGSN may store the address of the SGSN with which the GGSN established the last PDP context. This would prevent an enquiry to the HLR. This SGSN address would be considered as valid during a certain time.
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9.2.2.2.1  Successful Network-Requested PDP Context Activation ProcedureWord‑p. 246
The Successful Network-Requested PDP Context Activation procedure is illustrated in Figure 67.
Reproduction of 3GPP TS 23.060, Figure 67: Successful Network-Requested PDP Context Activation Procedure
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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 PDP PDUs received for the same PDP address.
2)
The GGSN may send Send Routeing Information for GPRS (IMSI) message to the HLR. If the HLR determines that the request can be served, it returns Send Routeing Information for GPRS Ack (IMSI, SGSN Address, Mobile Station Not Reachable Reason) message to the GGSN. 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 GSM 03.40). 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, APN) message to the SGSN indicated by the HLR. Otherwise, the GGSN shall set the MNRG flag for that MS. The GGSN shall not use PDP Type IPv4v6. The SGSN returns a PDU Notification Response (Cause) message to the GGSN 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, PDP Address, APN) 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").
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9.2.2.2.2  Unsuccessful Network-Requested PDP Context Activation Procedure
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 if 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, due to an Abnormal RLC condition, or due to 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"), 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.
  • 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"), the SGSN, the GGSN, and the HLR may perform the Protection and Mobile User Activity procedures.
The Protection procedure is illustrated in Figure 68.
Reproduction of 3GPP TS 23.060, Figure 68: Protection Procedure
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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 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 with Cause equal to "MS Not GPRS Responding" or "MS Refuses". The GGSN returns a PDU Notification Reject Response message to the SGSN.
3)
If Cause equals "IMSI Not Known", the GGSN may send Send Routeing Information for GPRS (IMSI) message to the HLR. The HLR returns Send Routeing Information for GPRS Ack (IMSI, SGSN Address, Cause) message to the GGSN indicating the address of the SGSN that currently serves the MS. If SGSN Address is different from the one previously stored by the GGSN, then steps 3, 4, and 5 in Figure 67 are followed.
4)
If SGSN 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 all PDP address(es) for that MS 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 69.
Reproduction of 3GPP TS 23.060, Figure 69: Mobile User Activity Procedure
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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 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 "GPRS Attach Function") to the HLR.
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 field is the address of the SGSN that currently serves the MS. Upon reception of Note MS Present each GGSN shall clear MNRG.
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