 masterCellGroup OCTET STRING (CONTAINING CellGroupConfig) OPTIONAL, - Need M radioBearerConfig 2 OCTET STRING (CONTAINING RadioBearerConfig) OPTIONAL, - Need M NR Standalone (i.e. NR connected to 5GC) supports two SRBs as in LTE. An additional SRB, SRB3, is introduced for direct RRC signaling to and from the SN when a UE is configured with dual connectivity (see Section 4.3). Up to 16 DRBs can be supported in NR. 3.4.5.2.2 Security Security procedures for NR are similar to LTE; that is, all RBs are encrypted and SRBs are also integrity protected. Additionally, integrity protection is introduced for DRBs and both encryption and integrity protection are configurable per DRB. Another difference to LTE is that not all handovers involve a change of security key. The reason for this is that inter-DU handover within a gNB-CU does not change the security location and hence such a han- dover does not require a key change. To cater for handovers without key change, the security 3.4 NR Protocol Stack configuration is not carried within the reconfigwithSync IE that triggers the handover procedure. The reconfigwithSync is carried within the CellGroupConfig put together by the gNB-DU while the security configuration is provided by the gNB-CU directly in the RRC Reconfig- uration message along with other possible configurations. 3.4.5.2.3 Mobility Apart from the abovementioned differences, the mobility procedures in NR are similar to other cellular technologies. Measurement configuration provided by a gNB to a UE indi- cates which objects (frequencies) to measure, what quantities should be measured, and the trigger events for measurement reporting. When a measurement report is triggered, the UE sends the report with the measured results to the gNB. If the source gNB decides to hand over the UE, it indicates SO to the target gNB via the Xn handover preparation procedure. The target then gNB reserves resources and provides the target cell configuration to source gNB, to be delivered to the UE over the source cell using the RRC R