A User Equipment, UE, comprising: a controller; and a transmission and/or reception unit characterised by being configured to: perform a communication by use of a control plane CloT EPS Optimisation, based on completion of an attach procedure; transmit a first control message to a core network during the communication by use of the control plane CloT EPS Optimisation, wherein the first control message includes a flag indicating that radio bearers establishment is requested; receive, from the core network, a second control message as a response to the first control message; and perform the communication by use of the radio bearers, based on receiving the second control message, 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, wherein the ATTACH REQUEST message includes UE capability information indicating support of the control plane CloT EPS Optimisation and information for a request to use the control plane CloT EPS Optimisation, and the ATTACH ACCEPT message includes network capability information indicating support of the control plane CloT EPS Optimisation, and the controller is configured to recognize that use of the communication by use of the control plane CloT EPS Optimisation is accepted, based on receiving the network capability information. a controller; and a transmission and/or reception unit characterised by being configured to: perform a communication by use of a control plane CloT EPS Optimisation, based on completion of an attach procedure; transmit a first control message to a core network during the communication by use of the control plane CloT EPS Optimisation, wherein the first control message includes a flag indicating that radio bearers establishment is requested; receive, from the core network, a second control message as a response to the first control message; and perform the communication by use of the radio bearers, based on receiving the second control message, wherein perform a communication by use of a control plane CloT EPS Optimisation, based on completion of an attach procedure; transmit a first control message to a core network during the communication by use of the control plane CloT EPS Optimisation, wherein the first control message includes a flag indicating that radio bearers establishment is requested; receive, from the core network, a second control message as a response to the first control message; and perform the communication by use of the radio bearers, based on receiving the second control message, 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, wherein the ATTACH REQUEST message includes UE capability information indicating support of the control plane CloT EPS Optimisation and information for a request to use the control plane CloT EPS Optimisation, and the ATTACH ACCEPT message includes network capability information indicating support of the control plane CloT EPS Optimisation, and 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, wherein the ATTACH REQUEST message includes UE capability information indicating support of the control plane CloT EPS Optimisation and information for a request to use the control plane CloT EPS Optimisation, and the ATTACH ACCEPT message includes network capability information indicating support of the control plane CloT EPS Optimisation, and the ATTACH REQUEST message includes UE capability information indicating support of the control plane CloT EPS Optimisation and information for a request to use the control plane CloT EPS Optimisation, and the ATTACH ACCEPT message includes network capability information indicating support of the control plane CloT EPS Optimisation, and the controller is configured to recognize that use of the communication by use of the control plane CloT EPS Optimisation is accepted, based on receiving the network capability information.