AT handling and allows for more focused inter-operability testing. The allowed inter-RAT state transitions are depicted in Figure 7.17 below. 7.7 The RRC Protocol EUTRA Handover RRC_CONNECTED RRC_CONNECTED Release Suspend Release Resume EUTRA RRC_INACTIVE RRC_INACTIVE Reselect Release Release Setup Setup EUTRA RRC_IDLE Reselect RRC_IDLE Figure 7.17 Mobility to and from NR. Table 7.2 SRB types in 5G. SRB type SRB usage Main purpose Connection Most RRC messages NAS and other Only for specific establishment, (both before and lower-priority EN-DC messages: resumption, and after AS security messages; only Measurement reestablishment (i.e. establishment); may configured after reporting and SCG messages requiring include NAS security activation reconfigurations UE identification) information before not involving MN security activation Channel Ciphering Before security activation: No After security activation: Yes Integrity protection Used only for EN-DC The RRC messages are sent using the SRBs, which always have higher priority than DRBs to ensure they are sent as quickly as possible. The SRBs 0-3 can be configured in NR for the following purposes, as shown in Table 7.2. 7.7.2 Broadcast of System Information System information contains both NAS and access stratum (AS)-related information. Based on the characteristics and usages of the information, the system information elements are grouped together into the MasterInformationBlock (MIB) and different SIBs. Generally, system information provides the UE the parameters to operate in RRC_IDLE and RRC_INACTIVE states and also provides sufficient information to 7 5G Radio Protocols move to RRC_CONNECTED. For a UE in RRC_CONNECTED, the network can provide system information through dedicated signaling using the RRCReconfiguration message, for example, if the UE has an active BWP with no common search space configured. Nevertheless, the UE shall acquire the MIB of the PSCell to get the SFN timing of the Secondary Cell Group (SCG) (which may be different from the Master Cell Gro