A User Equipment, UE, comprising: a transmission and/or reception unit configured to: perform communication by use of a first Cellular Internet of Things, CIoT, Evolved Packet System, EPS, Optimisation after completion of an attach procedure, transmit a first control message to a core network, receive a second control message as a response to the first control message from the core network, and perform communication by use of a second CIoT EPS Optimisation after receiving the second control message; and a control unit, wherein the transmission and/or reception unit, in the attach procedure, is configured to: transmit an Attach Request message to the core network, receive an Attach Accept message from the core network, and transmit an Attach Complete message to the core network, the Attach Request message includes UE capability information indicating support of the first CIoT EPS Optimisation and information indicating a request to use the first CIoT EPS Optimisation, the Attach Accept message includes network capability information indicating support of the first CIoT EPS Optimisation, the control unit receives the network capability information indicating the support of the first CIoT EPS Optimisation to interpret that use of the communication by use of the first CIoT EPS Optimisation is accepted, the first control message includes information indicating a request to use the second CIoT EPS Optimisation, the second control message includes information indicating the second CIoT EPS Optimisation, and the control unit receives the information indicating the second CIoT EPS Optimisation to interpret that use of the communication by use of the second CIoT EPS Optimisation is accepted. a transmission and/or reception unit configured to: perform communication by use of a first Cellular Internet of Things, CIoT, Evolved Packet System, EPS, Optimisation after completion of an attach procedure, transmit a first control message to a core network, receive a second control message as a response to the first control message from the core network, and perform communication by use of a second CIoT EPS Optimisation after receiving the second control message; and perform communication by use of a first Cellular Internet of Things, CIoT, Evolved Packet System, EPS, Optimisation after completion of an attach procedure, transmit a first control message to a core network, receive a second control message as a response to the first control message from the core network, and perform communication by use of a second CIoT EPS Optimisation after receiving the second control message; and a control unit, wherein the transmission and/or reception unit, in the attach procedure, is configured to: transmit an Attach Request message to the core network, receive an Attach Accept message from the core network, and transmit an Attach Complete message to the core network, transmit an Attach Request message to the core network, receive an Attach Accept message from the core network, and transmit an Attach Complete message to the core network, the Attach Request message includes UE capability information indicating support of the first CIoT EPS Optimisation and information indicating a request to use the first CIoT EPS Optimisation, the Attach Accept message includes network capability information indicating support of the first CIoT EPS Optimisation, the control unit receives the network capability information indicating the support of the first CIoT EPS Optimisation to interpret that use of the communication by use of the first CIoT EPS Optimisation is accepted, the first control message includes information indicating a request to use the second CIoT EPS Optimisation, the second control message includes information indicating the second CIoT EPS Optimisation, and the control unit receives the information indicating the second CIoT EPS Optimisation to interpret that use of the communication by use of the second CIoT EPS Optimisation is accepted.