A user equipment, UE comprising: a processor; and a memory, wherein the memory stores instructions that cause the processor to: determine whether a procedure to be performed is a first procedure or a second procedure, based on whether the UE transmits an RRCConnectionResumeRequest message while performing an early data transmission or the UE transmits the RRCConnectionResumeRequest message without performing the early data transmission, perform the first procedure, in a case that the UE transmits the RRCConnectionResumeRequest message while performing the early data transmission, wherein the first procedure is a procedure during which, upon an upper layer requests a resumption of an RRC connection, the UE restores a packet data convergence protocol, PDCP state, re-establishes PDCP entities for all data radio bearers, DRBs, indicates to lower layers that a stored UE access stratum, AS context is used, and resets a header compression protocol context for the DRBs configured with the header compression protocol, before transmitting the RRCConnectionResumeRequest message; perform the second procedure, in a case that the UE transmits the RRCConnectionResumeRequest message without performing the early data transmission, wherein the second procedure is a procedure during which, upon the upper layer requests a resumption of the RRC connection, the UE receives an RRCConnectionResume message, restores the PDCP state, and re-establishes the PDCP entities for all DRBs, after transmitting the RRCConnectionResumeRequest message. a processor; and a memory, wherein the memory stores instructions that cause the processor to: determine whether a procedure to be performed is a first procedure or a second procedure, based on whether the UE transmits an RRCConnectionResumeRequest message while performing an early data transmission or the UE transmits the RRCConnectionResumeRequest message without performing the early data transmission, perform the first procedure, in a case that the UE transmits the RRCConnectionResumeRequest message while performing the early data transmission, wherein the first procedure is a procedure during which, upon an upper layer requests a resumption of an RRC connection, the UE restores a packet data convergence protocol, PDCP state, re-establishes PDCP entities for all data radio bearers, DRBs, indicates to lower layers that a stored UE access stratum, AS context is used, and resets a header compression protocol context for the DRBs configured with the header compression protocol, before transmitting the RRCConnectionResumeRequest message; perform the second procedure, in a case that the UE transmits the RRCConnectionResumeRequest message without performing the early data transmission, wherein the second procedure is a procedure during which, upon the upper layer requests a resumption of the RRC connection, the UE receives an RRCConnectionResume message, restores the PDCP state, and re-establishes the PDCP entities for all DRBs, after transmitting the RRCConnectionResumeRequest message. determine whether a procedure to be performed is a first procedure or a second procedure, based on whether the UE transmits an RRCConnectionResumeRequest message while performing an early data transmission or the UE transmits the RRCConnectionResumeRequest message without performing the early data transmission, perform the first procedure, in a case that the UE transmits the RRCConnectionResumeRequest message while performing the early data transmission, wherein the first procedure is a procedure during which, upon an upper layer requests a resumption of an RRC connection, the UE restores a packet data convergence protocol, PDCP state, re-establishes PDCP entities for all data radio bearers, DRBs, indicates to lower layers that a stored UE access stratum, AS context is used, and resets a header compression protocol context for the DRBs configured with the header compression protocol, before transmitting the RRCConnectionResumeRequest message; perform the second procedure, in a case that the UE transmits the RRCConnectionResumeRequest message without performing the early data transmission, wherein the second procedure is a procedure during which, upon the upper layer requests a resumption of the RRC connection, the UE receives an RRCConnectionResume message, restores the PDCP state, and re-establishes the PDCP entities for all DRBs, after transmitting the RRCConnectionResumeRequest message.