Section: .2 Delete Bearer Request
Content: The direction of this message shall be from PGW to SGW, from SGW to MME/S4-SGSN and from PGW to TWAN/ePDG (see Table 6.1-1). A Delete Bearer Request message shall be sent on the S5/S8 and S4/S11 interfaces as part of the following procedures: - PGW or MME initiated bearer deactivation procedures, - UE requested Bearer Resource Modification, - MS and SGSN Initiated Bearer Deactivation procedure using S4 or - PGW initiated bearer deactivation procedure using S4. In the above cases, this Request is sent by the PGW to the SGW and shall be forwarded to the MME or S4-SGSN. The message shall also be sent on the S4/S11 interface by the SGW to the SGSN/MME to delete the bearer resources on the other ISR associated CN node if the ISRAI flag is not set in the Modify Bearer Request/Modify Access Bearers Request message. The message shall also be sent on the S4/S11 interface by the SGW to the SGSN/MME to delete the bearer resources on the other ISR associated CN node in the TAU/RAU/Handover procedures if the ISR related Cause IE is included in the Delete Session Request message. The message shall also be sent on the S2b interface by the PGW to the ePDG as part of PGW Initiated Bearer Resource Allocation Deactivation procedure with GTP on S2b. The message shall also be sent on the S2a interface by the PGW to the TWAN as part of the PGW Initiated Bearer Resource Allocation Deactivation in WLAN on GTP on S2a procedure. The message may also be sent on the S11/S4 interface by the SGW to the MME/S4 SGSN when the SGW receives the Error Indication from PGW for the default bearer or the ICMP message from a PGW that indicates the UE specific error indication as specified in 3GPP TS 23.007[ Restoration procedures ]  [17]. The message shall also be sent on the S5/S8 or S2a/S2b interface by the PGW to the SGW or to the TWAN/ePDG and on the S11/S4 interface by the SGW to the MME/S4-SGSN as part of the Network-initiated IP flow mobility procedure, as specified by 3GPP TS 23.161[ Network-Based IP Flow Mobility (NBIFOM); Stage 2 ]  [71]. The message shall also be sent on the S5/S8 interface by the PGW to the SGW, as part of EPS to 5GS mobility without N26 interface, ePDG/EPC to 5GS handover, EPS to 5GC/N3IWF handover, as specified in 3GPP TS 23.502[ Procedures for the 5G System (5GS) ]  [83]. If the UE uses NB-IoT, WB-EUTRAN or GERAN Extended Coverage with increased NAS transmission delay (see 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [23] and 3GPP TS 24.008[ Mobile radio interface Layer 3 specification; Core network protocols; Stage 3 ]  [5]), the MME/SGSN should proceed as specified for a UE in ECM-IDLE state with extended idle mode DRX enabled in clause 5.4.4.1 of 3GPP TS 23.401[ General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access ]  [3]. Possible Cause values are: - "RAT changed from 3GPP to Non-3GPP", - "ISR deactivation", - "Access changed from Non-3GPP to 3GPP", - "Reactivation requested", - "PDN reconnection to this APN disallowed", - "PDN connection inactivity timer expires", - "Local release", - "Multiple accesses to a PDN connection not allowed", - "EPS to 5GS Mobility". Table .2-1 specifies the presence of IEs in this message. Table .2-1: Information Elements in a Delete Bearer Request NOTE: In the case that the procedure was initiated by a UE Requested Bearer Resource Modification Procedure for an E-UTRAN as specified by 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [23], then there will be only one instance of the EPS Bearer IDs IE in the Delete Bearer Request. Table .2-2: Bearer Context within Delete Bearer Request Table 7.2.9.2-3: Load Control Information within Delete Bearer Request Table 7.2.9.2-4: Overload Control Information within Delete Bearer Request Table 7.2.9.2-5: PGW Change Info within Delete Bearer Request