Section: 5.4.7 E-UTRAN initiated E-RAB modification procedure
Content: When SCG bearer option is applied to support dual connectivity operation, this procedure is used to transfer bearer contexts to and from Secondary eNodeB (see TS 36.300[ Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 ]  [5]) or Secondary gNodeB (see TS 37.340[ Evolved Universal Terrestrial Radio Access (E-UTRA) and NR; Multi-connectivity; Overall Description; Stage-2 ]  [85]). During this procedure, both the MME and Serving GW are never relocated. The presence of IP connectivity between the Serving GW and the Master eNodeB (see TS 36.300[ Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 ]  [5] or TS 37.340[ Evolved Universal Terrestrial Radio Access (E-UTRA) and NR; Multi-connectivity; Overall Description; Stage-2 ]  [85] for Master eNodeB definition), as well as between the Serving GW and the Secondary RAN node is assumed. NOTE: In E-UTRAN, eNodeB is not allowed to negotiate bearer-level QoS parameters as defined in clause 4.7.2.1. Figure 5.4.7-1: E-UTRAN initiated E-RAB modification procedure 1. The Master eNodeB sends a E-RAB Modification Indication message (eNodeB address(es) and TEIDs for downlink user plane for all the EPS bearers, CSG Membership Information, Secondary RAT usage data) to the MME. The Master eNodeB indicates for each bearer whether it is modified or not. If the PLMN has configured secondary RAT usage reporting and the eNodeB has Secondary RAT usage data to report, the Secondary RAT usage data is included. The eNodeB shall include the ECGI and, if Dual Connectivity is activated for the UE, the PSCell ID, in the E-RAB Modification Indication message. If the Secondary eNodeB is a hybrid access eNodeB, the Master eNodeB includes the CSG Membership Information for the SCG bearer(s) in the E-RAB Modification Indication message. The MME determines the CSG membership based on the CSG Membership Information as specified in TS 36.300[ Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 ]  [5], but does not update the User CSG Information in the Core Network. A failure of the CSG Membership Information verification does not impact the E-UTRAN initiated E-RAB modification procedure. 2. The MME sends a Modify Bearer Request (eNodeB address(es) and TEIDs for downlink user plane for all the EPS bearers, ISR Activated, User Location Information, PSCell ID, Secondary RAT usage data and indication to send it to PDN GW) message per PDN connection to the Serving GW, only for the affected PDN connections. If ISR was activated before this procedure, MME should maintain ISR. The UE is informed about the ISR status in the Tracking Area Update procedure. If the Serving GW supports Modify Access Bearers Request procedure and if there is no need for the SGW to send the signalling to the PDN GW, the MME may send a Modify Access Bearers Request (eNodeB address(es) and TEIDs for downlink user plane for all the EPS bearers, ISR Activated) to the Serving GW to optimise the signalling. If the MME received Secondary RAT usage data in step 1, the MME shall include it in this message. If the MME received PSCell ID in step 1, the MME shall include it in this message. If Secondary RAT usage data was included and if PGW secondary RAT usage data reporting is active, the Serving GW shall send Modify Bearer Request (Secondary RAT usage data) message to the PDN GW for each PDN connection. The PDN GW responds with Modify Bearer Response message to the Serving GW. 3. The Serving GW returns a Modify Bearer Response (Serving GW address and TEID for uplink traffic) message to the MME as a response to a Modify Bearer Request message, or a Modify Access Bearers Response (Serving GW address and TEID for uplink traffic) as a response to a Modify Access Bearers Request message. The Serving GW starts sending downlink packets to the eNodeB using the newly received address and TEID. 4. In order to assist the reordering function in the Master eNodeB and/or Secondary RAN nodes, for the bearers that are switched between Master eNodeB and Secondary RAN nodes, the Serving GW shall send one or more "end marker" packets on the old path immediately after switching the path as defined in TS 36.300[ Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 ]  [5], clause 10.1.2.2. 5. The MME confirms the E-RAB modification with the E-RAB Modification Confirm (CSG Membership Status) message. The MME indicates for each bearer whether it was successfully modified, kept unmodified or already released by the EPC as defined in TS 36.413[ Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 Application Protocol (S1AP) ]  [36]. For the EPS bearers that have not been switched successfully in the core network, it is the MME decision whether to maintain or release the corresponding EPS bearers. The eNodeB uses the CSG Membership Status to decide on further actions, as specified in TS 36.300[ Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 ]  [5].