 PDUs from radio bearer X and one RLC PDU from radio bearer y. The RLC PDUs from radio bearer X each corresponds to one IP packet (n and n + 1) while the RLC PDU from radio bearer y is a segment of an IP packet (m) [8]. The services and functions of the RRC sublayer include broadcast of SI related to access stra- tum (AS) and NAS, as well as paging initiated by 5GC or NG-RAN (paging initiated by NG- RAN is a new NR feature). The RRC sublayer services further includes establishment, mainte- nance, and release of an RRC connection between the UE and NG-RAN that consist of addi- tion, modification, and release of carrier aggregation; addition, modification, and release of 200 Chapter 2 dual connectivity (DC) between LTE and NR. The security functions including key manage- ment, establishment, configuration, maintenance, and release of signaling and DRBs as well as mobility management, which comprises handover and context transfer; UE cell selection and reselection and control of cell selection and reselection; inter-RAT mobility; QoS management functions; UE measurement reporting and control of the reporting; detection of and recovery from radio link failure (RLF); and NAS message transfer are among other services provided by the RRC sublayer [8,15]. An NR UE at any time is in one of the three RRC states that are defined as follows [8]: RRC_IDLE which is characterized by PLMN selection; broadcast of system informa- tion; cell reselection; paging for mobile terminated data is initiated by 5GC; and discon- tinuous reception (DRX) for core-network paging configured by NAS. RRC_INACTIVE which is characterized by PLMN selection; broadcast of system infor- mation; cell reselection; paging initiated by NG-RAN (RAN paging); RAN-based notifi- cation area (RNA) is managed by NG-RAN; DRX for RAN paging configured by NG- RAN; 5GC and NG-RAN connection (both control and user-planes) establishment for the UEs; storage of UE AS context in NG-RAN and the UE; and NG-RAN knowledge of UE location at RNA-level. RRC_CONNECTED which is c