Section: 5.3.8.3A SGSN-initiated Detach procedure with ISR activated
Content: The SGSN-Initiated Detach procedure with ISR activated is illustrated in Figure 5.3.8.3A-1. Refer to clause 6.6.2.1 of TS 23.060[ General Packet Radio Service (GPRS); Service description; Stage 2 ]  [7] for the SGSN-initiated Detach procedure when ISR is not activated. Figure 5.3.8.3A-1: SGSN-Initiated Detach Procedure with ISR activated NOTE 1: For a PMIP-based S5/S8, procedure steps (A) are defined in TS 23.402[ Architecture enhancements for non-3GPP accesses ]  [2]. Steps 3, 4 and 5 concern GTP based S5/S8. 1. The SGSN initiated detach procedure is either explicit (e.g. by O&M intervention) or implicit. The SGSN may implicitly detach a UE, if it has not had communication with UE for a long period of time. The SGSN does not send the Detach Request (Detach Type) message to the UE for implicit detach. The implicit detach is local to the SGSN, i.e. an MME registration will not be detached. If the UE is in PMM-CONNNECTED state the SGSN may explicitly detach the UE by sending a Detach Request message to the UE. The Detach Type may be set to re-attach in which case the UE should re-attach at the end of the detach process. If the UE is in PMM-IDLE state the SGSN pages the UE. If this Detach procedure is due to the UE's Detach Request via a CSG cell which the UE is not allowed to access, i.e. the CSG subscription for this CSG ID and associated PLMN is absent or expired, the SGSN shall send a Detach Request to UE with an appropriate cause indicating the UE is not allowed to access this CSG. 2. Any EPS Bearer Context information in the Serving GW regarding this particular UE and related to the SGSN is deactivated by the SGSN sending Delete Session Request (LBI, User Location Information (ECGI)) message per PDN connection to the Serving GW. If the UE Time Zone has changed, the SGSN includes the UE Time Zone IE in this message. 3. Because the Serving GW receives this message in ISR activated state, the Serving GW deactivates ISR, releases the SGSN related EPS Bearer context information and acknowledges with Delete Session Response (Cause). 4. Because ISR is activated, the SGSN sends Detach Notification (Cause) message to the associated MME. The cause indicates whether it is a local or complete detach. 5. If cause indicates complete detach then the MME sends a Delete Session Request (LBI, User Location Information (ECGI)) message per PDN connection to the Serving GW. If Cause indicates local detach then MME deactivates ISR and steps 5 to 9 shall be skipped. If the UE Time Zone has changed, the MME includes the UE Time Zone IE in this message. 6. The Serving GW sends a Delete Session Request (LBI, User Location Information (ECGI or CGI/SAI)) message per PDN connection to the PDN GW. This message indicates that all bearers belonging to that PDN connection shall be released. If the MME and/or SGSN sends UE's Location Information and/or UE Time Zone in step 2 and/or step 5, the S-GW includes the User Location Information and/or UE Time Zone Information with the least age in this message. 7. The PDN GW acknowledges with Delete Session Response (Cause) message. 8. The PDN GW employs an IP CAN Session Termination procedure as defined in TS 23.203[ Policy and charging control architecture ]  [6] with the PCRF to indicate to the PCRF that the EPS Bearer(s) are released if a PCRF is configured. If requested by the PCRF the PDN GW indicates User Location Information and/or UE Time Zone Information to the PCRF as defined in TS 23.203[ Policy and charging control architecture ]  [6]. 9. The Serving GW acknowledges with Delete Session Response (Cause) message. 10. The MME sends Detach Acknowledge message to the SGSN. 11. If the UE receives the Detach Request message from the SGSN in the step 1, the UE sends a Detach Accept message to the SGSN any time after step 1. If the UE receives Detach Request from the SGSN via a CSG cell with the cause indicating the UE is not allowed to access this CSG, the UE shall remove this CSG ID and associated PLMN from its Allowed CSG list, if present. 12. After receiving the Detach Accept message, if Detach Type did not request the UE to make a new attach, then the 3G SGSN releases the PS signalling connection.