A User Equipment, UE, comprising: a transmission and/or reception unit configured to perform an attach procedure; and a control unit, wherein in the attach procedure, the transmission and/or reception unit is further configured to: transmit an ATTACH REQUEST message to a Mobility Management Entity, MME; receive an ATTACH ACCEPT message from the MME; and transmit an ATTACH COMPLETE message to the MME, the UE indicates that, based on transmitting the ATTACH REQUEST message, the UE requests to use a first processing, the ATTACH ACCEPT message includes network capability information indicating that performing for a second processing, among the first processing and the second processing, is supported, the control unit is configured to: interpret that performing for the second processing is accepted, based on receiving the network capability information, and perform at least the second processing after completion of the attach procedure, based on acceptance of performing of the second processing, the first processing is a processing that the UE transmits and/or receives user data via the MME by using a communication path for transmitting and/or receiving a control message, and the second processing is a processing that the UE enters an idle mode with keeping a UE context, in a case that a message to suspend a Radio Resource Control, RRC, connection is received from a base station device (45, 72, 76). a transmission and/or reception unit configured to perform an attach procedure; and a control unit, in the attach procedure, the transmission and/or reception unit is further configured to: transmit an ATTACH REQUEST message to a Mobility Management Entity, MME; receive an ATTACH ACCEPT message from the MME; and transmit an ATTACH COMPLETE message to the MME, transmit an ATTACH REQUEST message to a Mobility Management Entity, MME; receive an ATTACH ACCEPT message from the MME; and transmit an ATTACH COMPLETE message to the MME, the UE indicates that, based on transmitting the ATTACH REQUEST message, the UE requests to use a first processing, the ATTACH ACCEPT message includes network capability information indicating that performing for a second processing, among the first processing and the second processing, is supported, the control unit is configured to: interpret that performing for the second processing is accepted, based on receiving the network capability information, and perform at least the second processing after completion of the attach procedure, based on acceptance of performing of the second processing, interpret that performing for the second processing is accepted, based on receiving the network capability information, and perform at least the second processing after completion of the attach procedure, based on acceptance of performing of the second processing, the first processing is a processing that the UE transmits and/or receives user data via the MME by using a communication path for transmitting and/or receiving a control message, and the second processing is a processing that the UE enters an idle mode with keeping a UE context, in a case that a message to suspend a Radio Resource Control, RRC, connection is received from a base station device (45, 72, 76).