Title of Invention: TERMINAL DEVICE, BASE STATION DEVICE, METHOD, AND INTEGRATED CIRCUIT Abstract: A terminal apparatus includes a receiver configured to receive a first message and a controller configured to perform a measurement based on a measurement configuration included in the first message. The measurement configuration is associated with a secondary cell group. The controller releases the measurement configuration based on a release of Multi Radio access technology (RAT)-Dual Connectivity (MR-DC). Detailed Description: The present invention relates to a terminal apparatus, a base station apparatus, a method, and an integrated circuit. This application is the National Stage of International Patent Application No. PCT/JP2020/004487, filed on Feb. 6, 2020, which claims priority to and benefit of Japanese Patent Application JP 2019-20708 filed in Japan on Feb. 7, 2019, the contents of which are incorporated herein by reference. TECHNICAL FIELD Background Art A radio access method and a radio network for cellular mobile communications (which will hereinafter be referred to as “Long Term Evolution (LTE; trade name)” or “Evolved Universal Terrestrial Radio Access (E-UTRA)”) and a core network (which will be referred to as “Evolved Packet Core or EPC”) have been studied by the 3rd Generation Partnership Project (3GPP). As a radio access method and a radio network technology for a 5th generation cellular system, technical studies and standardization of LTE-Advanced Pro which is an enhanced technology of LTE and New Radio technology (NR) which is a new radio access technology have been conducted by the 3GPP (NPL 1). 5th Generation Core Network (5GC), which is a core network for the 5th generation cellular system, has also been studied (NPL 2). CITATION LIST Non-Patent Literature NPL 1: 3GPP RP-170855, “Work Item on New Radio (NR) Access Technology” NPL 2: 3GPP TS 23.501, v15.3.0, “System Architecture for the 5G System; Stage 2” NPL 3: 3GPP TS 36.300, v15.3.0, “Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2” NPL 4: 3GPP TS 36.331, v15.3.0, “Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specifications” NPL 5: 3GPP TS 36.323, v15.3.0, “Evolved Universal Terrestrial Radio Access (E-UTRA); Packet Data Convergence Protocol (PDCP) specification” NPL 6: 3GPP TS 36.322, v15.3.0, “Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Link Control (RLC) protocol specification” NPL 7: 3GPP TS 36.321, v15.3.0, “Evolved Universal Terrestrial Radio Access (E-UTRA); Medium Access Control (MAC) protocol specification” NPL 8: 3GPP TS 37.340, v15.4.0, “Evolved Universal Terrestrial Radio Access (E-UTRA) and NR; Multi-Connectivity; Stage 2” NPL 9: 3GPP TS 38.300, v15.3.0, “NR; NR and NG-RAN Overall description; Stage 2” NPL 10: 3GPP TS 38.331, v15.3.0, “NR; Radio Resource Control (RRC); Protocol specifications” NPL 11: 3GPP TS 38.323, v15.3.0, “NR; Packet Data Convergence Protocol (PDCP) specification” NPL 12: 3GPP TS 38.322, v15.3.0, “NR; Radio Link Control (RLC) protocol specification” NPL 13: 3GPP TS 38.321, v15.3.0, “NR; Medium Access Control (MAC) protocol specification” NPL 14: 3GPP TS 23.401 v15.0.0, “General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access” NPL 15: 3GPP TS 23.502, v15.3.0, “Procedure for 5G System; Stage 2” NPL 16: 3GPP TS 37.324, v15.1.0, “NR; Service Data Adaptation Protocol (SDAP) Specification” NPL 17: 3GPP RP-161266, “5G Architecture Options-Full Set” SUMMARY OF INVENTION Technical Problem As one of the technical studies of NR and other radio access technologies (RATs), a mechanism called Multi-RAT Dual Connectivity (MR-DC) is being studied that allows cells of RATs of both E-UTRA and NR to be grouped into a cell group on a RAT basis and to be allocated to a UE, or two cell groups of NR to be allocated to a UE such that a terminal apparatus communicates with one or more base station apparatuses (NPL 8). However, since the formats and functions of the communication protocols used in E-UTRA and NR are different, or the core network utilized is different depending on the form of the MR-DC as described in NPL 8, there is a problem in that the protocol processing is complex compared to Dual Connectivity in existing LTE using only E-UTRA as the RAT and using only EPC, which is the core network of LTE, as the core network, and thus a base station apparatus and a terminal apparatus are not able to efficiently communicate with each other. In view of the circumstances described above, an object of one aspect of the present invention is to provide a terminal apparatus capable of efficiently communicating with a base station apparatus, a base station apparatus, a method used for the terminal apparatus, and an integrated circuit mounted in the terminal apparatus. Solution to Problem In order to accomplish the object described above, a first aspect of the present invention is a terminal apparatus including: a receiver configured to receive a first message; and a controller configured to perform a measurement based on a measurement configuration included in the first message, the measurement configuration being associated with a secondary cell group, wherein the controller releases the measurement configuration based on a release of Multi Radio access technology (RAT)-Dual Connectivity (MR-DC). A second aspect of the present invention is a base station apparatus including: a processing unit configured to notify a terminal apparatus, for which a secondary cell group of NR is configured in MR-DC, of a release of the MR-DC, wherein notification of the release of the MR-DC causes the terminal apparatus to release a measurement configuration associated with the secondary cell group. A third aspect of the present invention is a method applied to a terminal apparatus, the method including: receiving a first message; performing a measurement based on a measurement configuration included in the first message, the measurement configuration being associated with a secondary cell group; and releasing the measurement configuration based on a release of MR-DC. A fourth aspect of the present invention is a method applied to a base station apparatus, the method including: notifying a terminal apparatus, for which a secondary cell group of NR is configured in MR-DC, of a release of the MR-DC, wherein notification of the release of the MR-DC causes the terminal apparatus to release a measurement configuration associated with the secondary cell group. A fifth aspect of the present invention is an integrated circuit mounted on a terminal apparatus, the integrated circuit causing the terminal apparatus to: receive a first message; perform a measurement based on a measurement configuration included in the first message, the measurement configuration being associated with a secondary cell group; and release the measurement configuration based on a release of MR-DC. A sixth aspect of the present invention is an integrated circuit mounted on a base station apparatus, the integrated circuit causing the base station apparatus to: notify a terminal apparatus, for which a secondary cell group of NR is configured in MR-DC, of a release of the MR-DC, wherein notification of the release of the MR-DC causes the terminal apparatus to release a measurement configuration associated with the secondary cell group. These comprehensive or specific aspects may be implemented in a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be implemented in any combination of systems, apparatuses, methods, integrated circuits, computer programs, and recording media. Advantageous Effects of Invention According to one aspect of the present invention, a terminal apparatus can efficiently perform communication by reducing complexity of protocol processing. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic diagram of a communication system according to each embodiment of the present invention. FIG. 2 is a protocol stack diagram of the user plane (UP) and the control plane (CP) of a terminal apparatus and a base station apparatus in the E-UTRA radio access layer according to each embodiment of the present invention. FIG. 3 is a protocol stack diagram of the UP and the CP of a terminal apparatus and a base station apparatus in the NR radio access layer according to each embodiment of the present invention. FIG. 4 is a diagram illustrating an example of a procedure for various configurations in the RRC layer in each embodiment of the present invention. FIG. 5 is a block diagram illustrating a configuration of the terminal apparatus according to each embodiment of the present invention. FIG. 6 is a block diagram illustrating a configuration of the base station apparatus according to each embodiment of the present invention. FIG. 7 is an example of a processing method of the UE according to Embodiment 2 of the present invention. FIG. 8 is an example in which the release of the E-UTRA secondary cell group in the MR-DC is activated by the NR side within the UE according to Embodiment 2 of the present invention. FIG. 9 is an example of Abstract Syntax Notation One (ASN.1) description of information indicating that the release and the addition of the configuration for the secondary cell group are performed at the same time, included in the RRC reconfiguration message in FIG. 8, according to Embodiment 2 of the present invention. FIG. 10 is an example of a processing method of the UE according to Embodiment 3 of the present invention. FIG. 11 is an example in which the release of the NR secondary cell group in the MR-DC is activated by the E-UTRA side within the UE according to Embodiment 3 of the present invention. FIG. 12 is another example in which the release of the NR secondary cell group in the MR-DC is activated by the E-UTRA side within the UE according to Embodiment 3 of the present invention. FIG. 13 is an example in which the release of the NR secondary cell group in the MR-DC is activated within the UE according to Embodiment 3 of the present invention. FIG. 14 is another example in which the release of the NR secondary cell group in the MR-DC is activated within the UE according to Embodiment 3 of the present invention. DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. LTE (and LTE-A Pro) and NR may be defined as different RATs. NR may be defined as a technology included in LTE. LTE may be defined as a technology included in NR. LTE that is connectable to NR using Multi-RAT Dual Connectivity may be distinguished from existing LTE. LTE, in which the core network is 5GC, may be distinguished from conventional LTE, in which the core network is EPC. The present embodiment may be applied to NR, LTE, and other RATs. Terms associated with LTE and NR are used in the following description. However, the present invention may be applied to other technologies using other terms. The term “E-UTRA” in the present embodiment may be replaced with “LTE,” and the term “LTE” may be replaced with “E-UTRA”. FIG. 1 is a schematic diagram of a communication system according to each embodiment of the present invention. E-UTRA 100 is a radio access technology described in NPL 3 or the like, and includes a cell group (CG) configured in one or multiple frequency bands. An E-UTRAN Node B (eNB) 102 is a base station apparatus of E-UTRA 100. Evolved Packet Core (EPC) 104 is a core network described in NPL 14 or the like and is designed as a core network for E-UTRA 100. An interface 112 is provided between the eNB 102 and EPC 104, where there are a control plane (CP) through which control signals are transferred and a user plane (UP) through which user data is transferred. NR 106 is a radio access technology described in NPL 9 or the like, and includes a cell group (CG) configured in one or multiple frequency bands. A gNode B (gNB) 108 is a base station apparatus of NR 106. 5GC 110 is a core network described in NPL 2 and the like, and is designed as a core network for NR 106, but may also be used as a core network for E-UTRA 100 which has a function to connect to 5GC 110. Hereinafter, E-UTRA 100 may have a function to connect to 5GC 110. An interface 114 is provided between the eNB 102 and 5GC 110, an interface 116 is provided between the gNB 108 and 5GC 110, an interface 118 is provided between the gNB 108 and EPC 104, an interface 120 is provided between the eNB 102 and the gNB 108, and an interface 124 is provided between EPC 104 and 5GC 110. The interface 114, the interface 116, the interface 118, the interface 120, the interface 124, and the like may transfer the CP only, the UP only, or both the CP and the UP. The interface 114, the interface 116, the interface 118, the interface 120, the interface 124, and the like may not exist depending on communication systems provided by network operators. A UE 122 is a terminal apparatus supporting NR 106 or both E-UTRA 100 and NR 106. As described in NPL 3 and/or NPL 9, in a case that the UE 122 connects to the core network via E-UTRA 100 and/or NR 106, a logical path called a Radio Bearer (RB) is established between the UE 122 and E-UTRA 100 and/or NR 106. The radio bearer used for the CP is referred to as a Signaling Radio Bearer (SRB), and the radio bearer used for the UP is referred to as a Data Radio Bearer (DRB). Each RB is assigned an RB identity (or RB ID) and is uniquely identified. The RB identity for the SRB is referred to as an SRB Identity (or SRB ID), and the RB identity for the DRB is referred to as a DRB Identity (or DRB ID). As described in NPL 3, in a case that the connected core network of the UE 122 is EPC 104, each DRB established between the UE 122 and E-UTRA 100 and/or NR 106 is further uniquely linked to each Evolved Packet System (EPS) bearer via EPC 104. Each EPS bearer is assigned an EPS bearer identity (or ID), and is uniquely identified. Data passing through the same EPS bearer ensures the same Quality of Service (QoS). As described in NPL 9, in a case that the connected core network of the UE 122 is 5GC 110, one or more DRBs established between the UE 122 and E-UTRA 100 and/or NR 106 are further linked to one of the Packet Data Unit (PDU) sessions established in 5GC 110. There are one or more QoS flows in each PDU session. Each DRB may be associated (mapped) with one or more QoS flows present in the linked PDU session, or may not be associated with any QoS flow. Each PDU session is identified with a PDU session identity (or ID). Each QoS flow is identified by the QoS flow identity. Data passing through the same QoS flow ensures the same QoS. There is no PDU session and/or QoS flow for EPC 104 and there is no EPS bearer for 5GC 110. In other words, in a case that UE 122 is connected to EPC 104, the UE 122 has information of the EPS bearer, and in a case that the UE 122 is connected to 5GC 110, the UE 122 has information of the PDU session and/or QoS flow. FIG. 2 is a protocol stack diagram of the UP and the CP of a terminal apparatus and a base station apparatus in the E-UTRA radio access layer according to each embodiment of the present invention. FIG. 2(A) is a protocol stack diagram of the UP used in a case that the UE 122 communicates with the eNB 102 in E-UTRA 100. A physical layer (PHY) 200 is a radio physical layer for providing a transmission service to a higher layer by using a physical channel. The PHY 200 is connected with a Medium Access Control layer (MAC) 202, which is a higher layer to be described below, via transport channels. Data is exchanged between the MAC 202 and the PHY 200 via the transport channels. The data is transmitted and/or received via radio physical channels between the PHYs of the UE 122 and the eNB 102. The MAC 202 is a medium access control layer for mapping various logical channels to various transport channels. The MAC 202 is connected with a radio link control layer (RLC) 204, which is a higher layer to be described below, via logical channels. The major classifications of the logical channel depend on the type of information to be transmitted; specifically, the logical channels are classified into control channels for transmitting control information and traffic channels for transmitting user information. The MAC 202 has a function of controlling the PHY 200 in order to perform the Discontinuous Reception (DRX) and Discontinuous Transmission (DTX), functions of performing a random access procedure, functions of reporting transmit power information, functions of performing Hybrid Automatic Repeat Request (HARQ) control, and the like (NPL 7). A Radio Link Control layer (RLC) 204 is a radio link control layer which divides (Segmentation) the data received from a Packet Data Convergence Protocol layer (PDCP) 206, which is a higher layer to be described below, and adjusts the data size such that a lower layer can properly perform data transmission. The RLC 204 also has a function of ensuring QoS required for each piece of data. In other words, the RLC 204 has a function of data retransmission control or the like (NPL 6). A PDCP 206 is a packet data convergence protocol layer for efficiently transmitting Internet Protocol (IP) packets, which are user data, in radio segments. The PDCP 206 may have a header compression function of compressing unnecessary control information. The PDCP 206 may also have a data encryption function (NPL 5). Note that data processed in the MAC 202, the RLC 204, and the PDCP 206 are referred to as a MAC Protocol Data Unit (PDU), an RLC PDU, and a PDCP PDU, respectively. Data delivered from a higher layer to the MAC 202, the RLC 204, and the PDCP 206 or data delivered therefrom to a higher layer are respectively referred to as a MAC Service Data Unit (SDU), an RLC SDU, and a PDCP SDU. FIG. 2(B) is a protocol stack diagram of the CP used in a case that the UE 122 communicates with the eNB 102 and a Mobility Management Entity (MME), which is a logical node for providing a function of authentication, mobility management, and the like, in E-UTRA 100. In addition to the PHY 200, the MAC 202, the RLC 204, and the PDCP 206, there are a Radio Resource Control layer layer (RRC) 208 and a Non-Access Stratum layer (NAS) (not explicitly shown in FIG. 2(B)) in the protocol stack of the CP. The RRC 208 is a radio link control layer that performs controls or the like of logical channels, transport channels, and physical channels, by performing processing such as establishing, re-establishing, suspending, or resuming an RRC connection, or performing reconfiguration of an RRC connection, for example, establishment, change, release or the like of a Radio Bearer (RB) and a Cell Group, as well as performs configuration of handover and measurement (measurement), and the like. The RBs may be classified into a Signaling Radio Bearer (SRB) and a Data Radio Bearer (DRB), and the SRB may be used as a path for transmitting an RRC message which is control information. The DRB may be used as a path for transmitting the user data. Each RB may be configured in the RRCs 208 of the eNB 102 and the UE 122. A portion of the RBs configured by the RLC 204 and the MAC 202 may be referred to as an RLC bearer (NPL 4). Some or all layers of the PHY 200, the MAC 202, the RLC 204, the PDCP 206, and the RRC 208 carrying signals between the UE 122 and the eNB 102 may be referred to as an Access Stratum (AS) layer, in comparison with the NAS layer carrying signals between the MME and the UE 122. The functional classification of the MAC 202, the RLC 204, the PDCP 206, and the RRC 208 described above is an example, and some or all of the respective functions may not be implemented. Some or all of the functions of each layer may be included in another layer. Note that an IP layer, and a Transmission Control Protocol (TCP) layer, a User Datagram Protocol (UDP) layer, an application layer, and the like that are higher layers than the IP layer, are higher layers than the PDCP layer (not illustrated). The RRC layer and the Non-Access Stratum (NAS) layer are also higher layers of the Service Data Application Protocol (SDAP) layer (not illustrated). In other words, the PDCP layer is a lower layer of the RRC layer, the NAS layer, and the IP layer, and the Transmission Control Protocol (TCP) layer, the User Datagram Protocol (UDP) layer, and the application layer that are higher layers than the IP layer. FIG. 3 is a protocol stack diagram of the UP and the CP of a terminal apparatus and a base station apparatus in the NR radio access layer according to each embodiment of the present invention. FIG. 3(A) is a protocol stack diagram of the UP used in a case that the UE 122 communicates with the gNB 108 in NR 106. A physical layer (PHY) 300 is a radio physical layer of NR and may provide a transmission service to a higher layer by using the physical channels. The PHY 300 may be connected with a Medium Access Control layer (MAC) 302 of a higher layer to be described below via the transport channels. Data may be exchanged between the MAC 302 and the PHY 300 via the transport channels. The data may be transmitted and/or received between the PHYs of the UE 122 and the gNB 108 via the radio physical channels. The MAC 302 is a medium access control layer for mapping various logical channels to various transport channels. The MAC 302 may be connected with a Radio Link Control layer (RLC) 304 of a high layer to be described below via the logical channels. The classification of the logical channels depends on the types of information to be transmitted, and the logical channels may be classified into the control channels for transmitting the control information and the traffic channels for transmitting the user information. The MAC 302 may have a function of controlling the PHY 300 in order to perform the DRX and DTX, a function of performing the random access procedure, a function of reporting the transmit power information, a function of performing the HARQ control, and the like (NPL 13). The RLC 304 is a radio link control layer which divides (Segmentation) the data received from a Packet Data Convergence Protocol Layer (PDCP) 206, which is a higher layer to be described below, and adjusts the data size such that a lower layer can properly perform data transmission. The RLC 304 may also have a function of ensuring QoS required for each piece of data. In other words, the RLC 304 may have a function of data retransmission control or the like (NPL 12). The PDCP 306 is a packet data convergence protocol layer for efficiently transmitting IP packets (IP packets), which are user data, in radio segments. The PDCP 306 may have a header compression function of compressing unnecessary control information. The PDCP 306 may also have a data encryption function (NPL 11). An SDAP 310 is a service data adaptation protocol layer having a function of mapping a QoS flow of a downlink transmitted from 5GC 110 to a terminal apparatus through a base station apparatus and a DRB, mapping a QoS flow of an uplink transmitted from the terminal apparatus to 5GC 110 through the base station apparatus and the DRB, and storing mapping rule information (NPL 16). FIG. 3(B) is a protocol stack diagram of the CP used in a case that the UE 122 communicates with the gNB 108 and an Access and Mobility Management Function (AMF), which is a logical node for providing a function of authentication, mobility management, and the like, in NR 106. In addition to the PHY 300, the MAC 302, the RLC 304, and the PDCP 306, there are an RRC Layer 308 and a NAS 312 in the protocol stack of the CP. The RRC 308 is a radio link control layer that performs controls or the like of logical channels, transport channels, and physical channels, by performing processing such as establishing, re-establishing, suspending, or resuming an RRC connection, or performing reconfiguration of an RRC connection, for example, establishment, change, release or the like of a Radio Bearer (RB) and a Cell Group, as well as performs configuration of handover and measurement (measurement), and the like. The RBs may be classified into an SRB and a DRB, and the SRB may be used as a path for transmitting an RRC message, which is control information. The DRB may be used as a path for transmitting the user data. Each RB may be configured between the RRCs 308 of the gNB 108 and the UE 122. A portion of the RBs configured by the RLC 304 and the MAC 302 may be referred to as an RLC bearer (NPL 10). Some or all layers of the PHY 200, the MAC 202, the RLC 204, the PDCP 206, and the RRC 208 carrying signals between the UE 122 and the gNB 108 may be referred to as an Access Stratum (AS) layer, in comparison with the NAS layer carrying signals between the AMF and the UE 122. The functional classification of the MAC 302, the RLC 304, the PDCP 306, the SDAP 310, and the RRC 308 described above is an example, and some or all of the functions may not be implemented. Some or all of the functions of each layer may be included in another layer. Note that each of the layers configured in the terminal apparatus and/or the base station apparatus may be referred to as an entity. In other words, the MAC layer, the RLC layer, the PDCP layer, the SDAP layer, and the RRC layer configured in the terminal apparatus and/or the base station apparatus may be referred to as a MAC entity, an RLC entity, a PDCP entity, an SDAP entity, and an RRC entity. Note that, hereinafter, in each embodiment of the present invention, in order to distinguish the E-UTRA protocol and the NR protocol from each other, the MAC 202, the RLC 204, the PDCP 206, and the RRC 208 may be respectively referred to as a MAC for E-UTRA or a MAC for LTE, an RLC for E-UTRA or an RLC for LTE, a PDCP for E-UTRA or a PDCP for LTE, and an RRC for E-UTRA or an RRC for LTE. The MAC 302, the RLC 304, the PDCP 306, and the RRC 308 may also be referred to as MAC for NR, RLC for NR, RLC for NR, and RRC for NR, respectively. Alternatively, there may be descriptions using a space such as an E-UTRA PDCP or an LTE PDCP, an NR PDCP, and the like. As also illustrated in FIG. 1, the eNB 102, the gNB 108, EPC 104, and 5GC 110 may be connected to one another via the interface 112, the interface 116, the interface 118, the interface 120, and the interface 114. Thus, the RRC 208 in FIG. 2 may be replaced with the RRC 308 in FIG. 3 to support various communication systems. The PDCP 206 in FIG. 2 may also be replaced with the PDCP 306 in FIG. 3. The RRC 308 in FIG. 3 may include the function of the RRC 208 in FIG. 2. The PDCP 306 in FIG. 3 may be the PDCP 206 in FIG. 2. In E-UTRA 100, the NR PDCP may be used as the PDCP even in a case that the UE 122 communicates with the eNB 102. An SRB may be defined from the following SRB 0 to the SRB 3. The SRB 0 may be an SRB for an RRC message using a Common Control CHannel (CCCH) of the logical channel. The SRB 1 may be an SRB for an RRC message (which may include a piggybacked NAS message) and for an NAS message prior to the establishment of the SRB 2, and all of the Dedicated Control CHannels (DCCH) of the logical channel may be used. The SRB 2 may be an SRB for the NAS message, and all of the DCCHs of the logical channel may be used. The SRB 2 may have a lower priority than the SRB 1. The SRB 3 may be an SRB for a particular RRC message in a case that the UE 122 is configured with E-UTRA-NR Dual Connectivity (EN-DC), NG-RAN E-UTRA-NR Dual Connectivity (NGEN-DC), NR-DC, or the like, and all of the DCCHs of the logical channel may be used. Other SRBs may also be provided for other applications. Next, the state transitions of the UE 122 in LTE will be described. The UE 122 may be in the RRC_CONNECTED state in a case that an RRC connection has been established. The UE 122 may be in the RRC_INACTIVE state in a case that the RRC connection is paused (if the UE 122 connects to 5GC). If not, the UE 122 may be the RRC_IDLE state. Note that the UE 122 connected to EPC does not have the RRC_INACTIVE state, but pause of the RRC connection may be initiated by the E-UTRAN. In this case, in a case that the RRC connection is paused, the UE 122 retains the AS context of the UE and the identity (resumeIdentity) used for the resume to transition to the RRC_IDLE state. In a case that the UE 122 retains the AS context of the UE, the resume of the RRC connection is permitted by the E-UTRAN, and UE 122 needs to transition from the RRC_IDLE state to the RRC_CONNECTED state, the resume of the paused RRC connection may be initiated by a higher layer (e.g., the NAS layer). That is, the definition of the pause may be different between a UE 122 connected to EPC and a UE 122 connected to 5GC. Some or all of the procedures for resume from pause may be different between a case that the UE 122 is connected to EPC (in a case that the UE 122 is paused in the RRC_IDLE state) and a case that the UE 122 is connected to 5GC (in a case that the UE is paused in the RRC_INACTIVE state). The AS context of the UE held by the UE 122 may be information including some or all of a current RRC configuration, a current security context, a PDCP state including a RObust Header Compression (ROHC) state, a Cell Radio Network Temporary Identifier (C-RNTI) used in a source Primary Cell (PCell), a cell identity (cellIdentity), and a physical cell identity of the source PCell. Note that the AS context of the UE held by the eNB 102 and/or gNB 108 may include the same information as the AS context of the UE held by the UE 122, or may include information different from the information included in the AS context of the UE held by the UE 122. The security context may be information including some or all of a cryptographic key at the AS level, a Next Hop parameter (NH), a Next Hop Chaining Counter parameter (NCC) used for access key derivation of the next hop, an identity of the cryptographic algorithm of the selected AS level, and a counter used for replay protection. FIG. 4 is a diagram illustrating an example of a procedure for various configurations in the RRC 208 and/or the RRC 308 in each embodiment of the present invention. FIG. 4(A) is an example of a flow in a case that an RRC message is transmitted from a base station apparatus (eNB 102 and/or gNB 108) to a terminal apparatus (UE 122), and FIG. 4(B) is an example of a procedure in a case that an RRC message is transmitted from a terminal apparatus (UE 122) to a base station apparatus (eNB 102 and/or gNB 108). In FIG. 4(A), the base station apparatus generates an RRC message (step S400). The generation of the RRC message in the base station apparatus may be performed in a case that the base station apparatus distributes System Information (SI) or paging information, or may be performed in a case that the base station apparatus determines it is necessary for a specific terminal apparatus to perform processing, for example, in a case of configuration for security, reconfiguration of the RRC connection (processing (establishment, change, release, etc.) of the radio line bearer, processing (establishment, addition, change, release, etc.) of the cell group, measurement configuration, handover configuration, etc.), release of the RRC connected state, or the like. The generation of the RRC message may be performed in order to respond to an RRC message received from a specific terminal apparatus in step S408 described later, or may be performed at a time other than these. The RRC message includes parameters for various information notifications and configurations. In the specification for RRC, such as NPL 4 or NPL 10, these parameters are referred to as fields and/or information elements, and are described using a notation called Abstract Syntax Notation One (ASN.1). In FIG. 4(A), the base station apparatus then transmits the generated RRC message to the terminal apparatus (step S402). Next, the terminal apparatus performs a process in a case that processing such as a configuration is necessary in accordance with the received RRC message described above (step S404). In FIG. 4(B), the terminal apparatus generates an RRC message (step S406). The generation of the RRC message in the terminal apparatus may be performed in a case that a request for the base station apparatus occurs, for example, in a case of establishment of an RRC connection according to, for example, a request from a higher layer; re-establishment of an RRC connection according to detection of radio link failure, random access failure, radio synchronization failure, or the like; resume from the RRC connection suspend according to a request from a higher layer or a Radio Access Network (RAN) paging response, or may be performed in order to respond to the RRC message received from the base station apparatus at step S402 described above, or may be performed at a time other than these. Note that in the description of each embodiment, the “RRC connection suspend” is also referred to as “pause of RRC connection”. “Resume from RRC connection suspend” is also referred to as “resume of RRC connection (from a pause state)”. In FIG. 4(B), the terminal apparatus then transmits the generated RRC message to the base station apparatus (step S408). Next, the base station apparatus performs a process in a case that processing is necessary in accordance with the received RRC message described above (step S410). Note that the RRC message is not limited to the examples described above, and may be generated for other purposes as described in NPL 4, NPL 10, and the like. For example, the RRC message may be used for the configuration of Dual Connectivity (DC) or Multi-Radio Dual Connectivity (MR-DC) described in NPL 8. The Dual Connectivity (DC) may be a technique to perform data communication using radio resources of both cell groups constituted with two base station apparatuses (nodes), namely a Master Cell Group (MCG) constituted with a Master Node (MN) and a secondary cell group (Secondary Cell Group, SCG) constituted with a secondary node (Secondary Node, SN). The MR-DC described in NPL 8 may be a technique in which cells of Radio Access Technology (RAT) of both E-UTRA and NR are grouped into cell groups for each RAT and allocated to the UE, and data communication is performed using radio resources of both the MCG and the SCG. In the MR-DC, the master node may be a base station having primary RRC functions related to the MR-DC, for example, having functions of addition of a secondary node; establishment, change, and release of an RB; addition, change, and release of a MCG; handover; and the like, and the secondary node may be a base station having some RRC functions, for example, change and release of an SCG, and the like. In the MR-DC described in NPL 8, the RRC of the RAT on the master node side may be used for configuration of both the MCG and the SCG. For example, in E-UTRA-NR Dual Connectivity (EN-DC) (which is MR-DC in a case that the core network is EPC 104 and the master node is the eNB 102 (also referred to as an extended eNB 102), or NG-RAN E-UTRA-NR Dual Connectivity (NGEN-DC), which is MR-DC in a case that the core network is 5GC 110 and the master node is eNB 102), an RRC message of E-UTRA described in NPL 4 may be transmitted and/or received between the eNB 102 and the UE 122. In this case, the RRC message may include not only configuration information of LTE (E-UTRA), but also configuration information of NR described in NPL 10. The RRC message transmitted from the eNB 102 to the UE 122 may be transmitted to the UE 122 from the eNB 102 via the gNB 108. The configuration of the RRC message may be used in E-UTRA/5GC (option 5 described in NPL 17), which is non-MR-DC in which the eNB 102 (extended eNB) uses 5GC as the core network. Hereinafter, the EN-DC may include the NGEN-DC unless stated otherwise. In contrast, in the MR-DC described in NPL 8, an RRC message of NR described in NPL 10 may be transmitted and/or received between the gNB 108 and the UE 122 in NR-E-UTRA Dual Connectivity (NE-DC), which is one of MR-DC in a case that the core network is 5GC 110 and the master node is the gNB 108. In this case, the RRC message may include not only configuration information of NR, but also configuration information of LTE (E-UTRA) described in NPL 4. The RRC message transmitted from the gNB 108 to the UE 122 may be transmitted to the UE 122 from the gNB 108 via the eNB 102. In NR Dual Connectivity (NR-DC), which is MR-DC in a case that the core network is 5GC 110 and both the master node and the secondary node are the gNB 108, an RRC message of NR described in NPL 10 may be transmitted and/or received between the gNB 108 and the UE 122. The RRC message transmitted from the gNB 108 to the UE 122 may be transmitted to the UE 122 from the gNB 108 via another gNB 108. NR-DC may also be expressed as NN-DC, N2-DC, NR2-DC, or NRNR-DC. FIG. 5 is a block diagram illustrating a configuration of the terminal apparatus (UE 122) according to each embodiment of the present invention. Note that FIG. 5 illustrates only the main components closely related to an aspect of the present invention in order to avoid complexity of description. The UE 122 illustrated in FIG. 5 includes a receiver 500 configured to receive an RRC message or the like from the eNB 102 and/or the gNB 108, and a processing unit 502 configured to perform processing according to configuration information, such as various types of Information Elements (IEs), and/or various fields, and/or various conditions included in the received message. The processing unit 502 may perform processing to trigger a request or an indication from the MCG side to the SCG side within the UE 122 configured with DC. For example, within the UE 122 configured with MR-DC, the processing unit 502 may perform processing to trigger a request or an indication from the E-UTRA side to the NR side in the NGEN-DC or the EN-DC described in NPL 8, for example, or from the NR side to the E-UTRA side in the NE-DC described in NPL 8, for example. The processing unit 502 may perform processing activated from the MCG side on the SCG side within the UE 122 configured with DC. For example, the processing unit 502 may perform processing activated from the E-UTRA side on the NR side in the NGEN-DC or the EN-DC described in NPL 8, for example, or the processing unit 502 may perform processing activated from the NR side on the E-UTRA side in the NE-DC described in NPL 8, for example. Note that “the MR-DC is configured” may refer to “the MR-DC is processed”, or may refer to “the MR-DC is operated”. Note that the NR side and the E-UTRA side here may be the NR RRC and the E-UTRA RRC, respectively. FIG. 6 is a block diagram illustrating a configuration of the base station apparatus (eNB 102 and/or gNB 108) according to each embodiment of the present invention. Note that FIG. 6 illustrates only the main components closely related to an aspect of the present invention in order to avoid complexity of description. The eNB 102 and/or the gNB 108 illustrated in FIG. 6 includes a transmitter 600 configured to transmit an RRC message or the like to the UE 122, and a processing unit 602 configured to cause the processing unit 502 of the UE 122 to perform processing by creating and transmitting an RRC message including the configuration information to the UE 122, such as various Information Elements (IE), and/or various fields, and/or various conditions. Embodiment 1 Embodiment 1 of the present invention will be described. Embodiment 1 of the present invention will be described assuming MR-DC in which the MCG side is NR and the SCG side is NR, but the present invention is not limited thereto, and may be applied to other MR-DC. Note that each embodiment of the present invention may be implemented in combination with one or more other embodiments. Measurements will be described. In the following description, an example in which the gNB 108 uses an RRC message (RRC signaling) of NR is described, but this is not a limitation, and similar processing may be performed by the eNB 102 using an RRC message (RRC signaling) of LTE. Note that the information included in the message and/or the configuration of the message is an example and is not limited thereto. The gNB 108 transmits measurement configuration information elements (also referred to as measurement configuration) to the UE 122 by using an RRC reconfiguration (RRCReconfiguration) message of RRC signaling (radio resource control signal) (included in the RRC reconfiguration message). The UE 122 performs measurements, event assessments, and measurement reports on serving cells and neighbor cells (including listed cell and/or detected cells) according to information included in the reported measurement configuration. The listed cells are cells listed in measurement objects (cells notified as a neighbor cell list from the gNB 108 to the UE 122). The detected cells are cells that are detected by the UE 122 at the frequency and subcarrier spacing indicated by the measurement objects but not listed in the measurement objects (cells detected by the UE 122 itself that are not notified as the neighbor cell list). The UE 122 may have a variable VarMeasConfig to hold the notified measurement configuration. The UE 122 may have a variable VarMeasReportList to hold measurement information consistent with the reporting condition. In MR-DC, the UE 122 may individually have a variable VarMeasConfig for holding a first measurement configuration configured by the MCG (or for the MCG, or linked with the MCG) and a variable VarMeasReportList for holding the measurement information consistent with the reporting condition of the first measurement configuration, and a variable VarMeasConfig for holding a second measurement configuration configured by the SCG (or for the SCG, or liked with the SCG) and a variable VarMeasReportList for holding the measurement information consistent with the reporting condition of the second measurement configuration. In MR-DC, the UE 122 may individually have (manage) a timer controlled by the measurement configuration configured by the MCG (or for the MCG, or linked with the MCG) (for example, a timer used to periodically report measurement information based on the measurement configuration configured by the MCG or a timer T321 used for the measurement of the global identity, and the like), and a timer controlled by the measurement configuration configured by the SCG (or for the SCG, or liked with the SCG) (for example, a timer used to periodically report measurement information based on the measurement configuration configured by the SCG or a timer T321 used for the measurement of the global identity, and the like). Here, the timer names used for the same purpose in the MCG and the SCG may be the same name or different names. In a case that multiple SCGs are configured, the variable VarMeasConfig may be held for each SCG, or one variable VarMeasConfig may be held for all of the SCGs. The measurement configuration notified from the gNB 108 may be notified distinguished between the measurement configuration of the MCG and the measurement configuration of the SCG. For example, (A) the first RRC reconfiguration message may include the measurement configuration for the MCG, the field indicating information on the SCG of the MR-DC included in the first RRC reconfiguration message may include an encapsulated RRC reconfiguration message (second RRC reconfiguration message) of the SCG, and the second RRC reconfiguration message may include the measurement configuration for the SCG. At this time, the first RRC reconfiguration message notifying the measurement configuration of the MCG and the first RRC reconfiguration message notifying the measurement configuration of the SCG may be the same RRC reconfiguration message, or may be different RRC reconfiguration messages notified at different timings. Alternatively, (B) the measurement configuration of the MCG may be notified by the SRB 1, and the measurement configuration of the SCG may be notified by the SRB 3. Either or both of (A) and (B) may be considered for identification of the measurement configuration of the MCG and the measurement configuration of the SCG. Alternatively, the identification of the measurement configuration of the MCG and the measurement configuration of the SCG may be performed based on other information. The measurements have three types (intra-frequency measurements, inter-frequency measurements, and inter-radio access technology measurements (inter-RAT measurements)). The intra-frequency measurements are measurements on the downlink frequency of the serving cell. The inter-frequency measurements are measurements on frequencies different from the downlink frequency of the serving cell. The inter-RAT measurements are measurements on radio technologies (e.g., UTRA, Global System for Mobile Communications (GSM) Enhanced Data for Global Evolution (EDGE) Radio Access Network (RAN) (or GERAN), Code Division Multiple Access 2000 (CDMA2000), E-UTRA, etc.) different from the radio technology of the serving cell (e.g., NR). The measurement configuration may include some or all of an addition and/or modification list of measurement identities (measId), a removal list of measurement identities, an addition and/or modification list of measurement objects, a removal list of measurement objects, an addition and/or modification list of reporting configurations, a removal list of reporting configurations, a quantity configuration (quantityConfig), a measurement gap configuration (measGapConfig), and a serving cell quality threshold (s-Measure) configuration. Quantity Configuration (quantityConfig) The quantity configuration (quantityConfig) specifies a Layer 3 (L3) filtering coefficient in a case that the measurement objects are NR and/or E-UTRA measurement objects. The L3 filtering coefficient defines a ratio of the latest measurement result and the past filtering measurement result. The filtering result is used for event assessment in the UE 122. Measurement Gap Configuration (measGapConfig) The measurement gap configuration (measGapConfig) is utilized for the configuration of the measurement gap pattern or for the control of the activation/deactivation of the measurement gap. The measurement gap configuration may be independently configured for each cell, each cell group, each component carrier, each serving cell, or each predefined frequency range. Serving Cell Quality Threshold (s-Measure) The serving cell quality threshold (s-Measure) represents a threshold value for the quality of the serving cell and is utilized to control whether or not the UE 122 needs to perform a measurement. The serving cell quality threshold (s-Measure) is configured as a value for reference signal received power (RSRP). Measurement Identity (measId) Here, the measurement identity (measId) is utilized to link the measurement objects and the reporting configurations, specifically, link the measurement object identity (measObjectId) and the reporting configuration identity (reportConfigId). The measurement identity (measId) is associated with one measurement object identity (measObjectId) and one reporting configuration identity (reportConfigId). The measurement configuration can add, modify, or delete a relationship of measurement identities (measId), measurement objects, and reporting configurations. The removal list of measurement identities included in the measurement configuration includes a list of measurement identities, and the UE 122 performs the following processes (A) to (C) for each measurement identity included in the removal list of the measurement identities. (A) The entry of this measurement identity is deleted from the variable VarMeasConfig of the cell group of interest in the measurement configuration. (B) If included, the entry of the measurement report
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