Section: Update Bearer Request
Content: The direction of this message shall be from PGW to SGW and/or from SGW to MME/S4-SGSN, and/or from PGW to TWAN/ePDG (see Table 6.1-1). For GTP based S5/S8, the Update Bearer Request shall be sent by the PGW to the SGW and forwarded to the MME as part of the following procedures: - PGW Initiated Bearer Modification with Bearer QoS Update - HSS Initiated Subscribed QoS Modification - PGW Initiated Bearer Modification without Bearer QoS Update - UE Request Bearer Resource Modification procedure (see 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [23]) - UE requested bearer resource allocation procedure (see 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [23]) - P-CSCF restoration for 3GPP access (see 3GPP TS 23.380[ IMS Restoration Procedures ]  [61]) - USS UAV Authorization/Authentication (UUAA) procedure during Attach or UE-requested PDN connectivity procedures (see 3GPP TS 23.256[ Support of Uncrewed Aerial Systems (UAS) connectivity, identification and tracking; Stage 2 ]  [90]) - USS initiated UAV Re-authorization procedure in EPS (see 3GPP TS 23.256[ Support of Uncrewed Aerial Systems (UAS) connectivity, identification and tracking; Stage 2 ]  [90]) - Secondary DN authentication and authorization in EPS Interworking case (see clause 5.17.2.5 of 3GPP TS 23.501[ System architecture for the 5G System (5GS) ]  [82] and Annex H of 3GPP TS 23.502[ Procedures for the 5G System (5GS) ]  [83]) The message shall also be sent on the S5/S8 interface by the PGW to the SGW and on the S4 interface by the SGW to the SGSN as part of the following procedures: - PGW Initiated EPS Bearer Modification - Execution part of MS-Initiated EPS Bearer Modification - SGSN-Initiated EPS Bearer Modification Procedure using S4 - P-CSCF restoration for 3GPP access (see 3GPP TS 23.380[ IMS Restoration Procedures ]  [61]) The message shall also be sent on the S2a/S2b interface by the PGW to the TWAN/ePDG as part of the following procedures: - PGW Initiated Bearer Modification - HSS Initiated Subscribed QoS Modification - P-CSCF restoration for WLAN access (see 3GPP TS 23.380[ IMS Restoration Procedures ]  [61]) For PMIP based S5/S8, the Update Bearer Request shall be sent on the S11 interface by the SGW to the MME and on the S4 interface by the SGW to the SGSN. 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 or the UE-initiated IP flow mobility procedure, as specified by 3GPP TS 23.161[ Network-Based IP Flow Mobility (NBIFOM); Stage 2 ]  [71]. Table -1 specifies the presence requirements and the conditions of the IEs in the message. Table -1: Information Elements in an Update Bearer Request NOTE: In the case that the procedure was initiated by a UE Requested Bearer Resource Modification Procedure or UE Requested Bearer Resource Allocation Procedure for an E-UTRAN or MS initiated EPS bearer modification procedure, then there will be only one instance of the Bearer Contexts IE in the Update Bearer Request. Table -2: Bearer Context within Update Bearer Request Table 7.2.15-3: Load Control Information within Update Bearer Request Table 7.2.15-4: Overload Control Information within Update Bearer Request Table 7.2.15-5: PGW Change Info within Update Bearer Request