eplies with a Handover Complete message. The handover mechanism triggered by RRC signaling requires the UE to at least reset the MAC entity and reestablish RLC entity. The NR supports RRC-managed handovers with and without PDCP entity reestablishment. For DRBs using RLC-AM mode, PDCP can either be reestablished along with security key change or initiate a data recovery proce- dure without key change. For DRBs using RLC-UM mode and for SRBs the PDCP entity can be reestablished either together with security key change or to remain as it is without key change. Data forwarding, in-sequence delivery, and duplication avoidance during handover can be guaranteed, when the target gNB uses the same DRB configuration as the source gNB. The NR further supports timer-based handover failure procedure where the RRC connection reestablishment procedure is used for recovering from handover failure. New Radio Access Layer 2/3 Aspects and System Operation 253 In beam-level mobility, explicit RRC signaling is not required to trigger handover. The gNB provides the UE via RRC signaling the measurement configuration containing configura- tions of SSB/CSI-RS resources and resource sets, reports, and trigger states for triggering channel and interference measurements and reports. The beam-level mobility is performed at lower layers by means of physical layer and MAC layer control signaling, and the RRC is not required to know which beam is being used at any given time. The SSB-based beam- level mobility is based on the SSB associated with the initial DL BWP and can only be con- figured for the initial DL BWPs and for DL BWPs containing the SSB associated with the initial DL BWP. For other DL BWPs, the beam-level mobility can only be performed based on CSI-RS. 2.3.4 User Equipment Capability The UE capabilities in NR do not rely on UE categories. Unlike LTE, the NR UE categories are associated with fixed peak data rates and defined for marketing purposes; thus they are not signaled to the network. Instead, the network determines the uplin