E and INACTIVE The most basic task of the RRC protocol is establishment of the RRC connection for a UE that needs to transfer data. While the network may initiate the UE connection attempt Table 7.4 RRC messages that include RRC transaction identifier. RRC message Comments RRCReestablishment, RRCResume, Downlink message that has a response (setting RRCSetup up UE connectivity) RRCReconfiguration Downlink message that has a response (modifying RRC configuration) CounterCheck, SecurityModeCommand, Downlink message that has a response UECapabilityEnquiry (requesting the UE to provide information or acknowledge the network procedure) DLInformationTransfer Downlink message (the default rule) MobilityFromNRCommand, RRCRelease Downlink message (the default rule) Table 7.5 RRC messages that do not include RRC transaction identifier. RRC message Comments RRCReject Moving UE to IDLE via RRC connection rejection MIB, SIB1, Paging Broadcast messages MeasurementReport, FailureInformation, UE-originating messages with no response in DL LocationMeasurementIndication, UE assistanceInformation, ULInformationTransfer RRCSetupRequest, RRCResumeRequest, UE-originating messages that may not have a RRCResumeRequest1, RRCSystemInfoRequest, direct downlink response RRCReestablishmentRequest 7 5G Radio Protocols by paging the UE, the procedure always starts with the UE accessing the network via a random access procedure, which establishes the necessary uplink and downlink timing and identification protocols. RRC involvement in the connection setup procedure is rather simple: Once the handshake via random access is completed, the RRC layer identifies the UE and config- ures it with the basic (initial) RRC configuration that allows starting basic information exchange between the UE and the network. Once the RRC connection is set up, the UE RRC acknowledgment message also delivers the NAS information to the network to enable setting up of the remaining UP details (e.g. services and their configuration details). For this purpose, the basic R