JP2016220044A - Communication control device, terminal device and mobile communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a simplified procedure to cause a communication relay device, such as a gateway device, to relay communication between a terminal device and an external communication network.SOLUTION: A communication control device 22, which is used for a mobile communication network 10 connected to an external communication network (for example, Internet) 18 through a communication relay device 14, includes: a connection destination designation unit which generates connection destination information to designate a communication relay device 14 as the connection destination of a terminal device 12, when the terminal device 12 communicates with the external communication network 18 using a radio communication network 16 other than the mobile communication network 10; and a connection destination notification unit which transmits the connection destination information to the terminal device 12 through a control plane route of the mobile communication network 10.SELECTED DRAWING: Figure 2

Description

  The present invention relates to communication using a mobile communication network.

  Communication using a mobile communication network operated by a telecommunications carrier and a wireless communication network such as a wireless local area network (LAN) has been proposed. For example, Patent Document 1 and Patent Document 2 disclose configurations in which a terminal device such as a mobile phone communicates selectively using a mobile communication network and a wireless LAN.

JP 2005-529560 A JP 2008-271140 A

  By the way, in a gateway device installed between a mobile communication network and an external communication network such as the Internet, a function for ensuring communication security between the terminal device and the external communication network and filtering for restricting access to a specific site. There are cases where various functions such as these functions (hereinafter collectively referred to as “specific service functions”) are installed. Since the communication between the terminal device and the external communication network through the mobile communication network is relayed by the gateway device, the specific service function can be used effectively, but a wireless communication network such as a wireless LAN other than the mobile communication network is used. Since the intended gateway device does not intervene in the communication, the specific service function may not be used effectively.

  On the other hand, a mechanism for forcing the connection from the terminal device to the gateway device when communicating with an external communication network using a wireless communication network other than the mobile communication network can be assumed. There is a problem that complicated procedures such as these are required. In view of the above circumstances, an object of the present invention is to simplify a procedure for relaying communication between a terminal device and an external communication network to a communication relay device such as a gateway device.

  In order to solve the above problems, a communication control device according to a preferred aspect of the present invention is a communication control device in a mobile communication network connected to an external communication network via a communication relay device, the mobile communication A connection destination designating unit for generating connection destination information for designating a communication relay device as a connection destination of the terminal device when the terminal device communicates with an external communication network using a wireless communication network other than the network, and the mobile communication A connection destination notification unit that transmits connection destination information to the terminal device via a network control plane path.

  A terminal device according to a preferred aspect of the present invention is a terminal device capable of communication using a mobile communication network connected to an external communication network via a communication relay device, and wireless communication other than the mobile communication network A reception processing unit for receiving connection destination information for designating a communication relay device as a connection destination of the terminal device when communicating with an external communication network using a network, via a control plane path of the mobile communication network; and A communication processing unit that communicates with an external communication network via a communication path established via a wireless communication network with the communication relay device specified by the destination information.

  A mobile communication system according to a preferred aspect of the present invention includes a mobile communication network connected to an external communication network via a communication relay device, and a terminal device capable of communication using the mobile communication network. In the mobile communication system, the mobile communication network uses a communication relay device as a connection destination of the terminal device when the terminal device communicates with an external communication network using a wireless communication network other than the mobile communication network. A destination specifying unit that generates connection destination information to be specified; and a connection destination notifying unit that transmits connection destination information to the terminal device via a control plane path of the mobile communication network. Communication that communicates with an external communication network via a communication path established via a wireless communication network between the reception processing unit that receives the connection destination information via the path and the communication relay device specified by the connection destination information And a processing unit.

  In the present invention, when a terminal device communicates with an external communication network using a wireless communication network, connection destination information for designating a communication relay device to be connected by the terminal device is transmitted from the communication control device of the mobile communication network to the terminal device. Therefore, the procedure for relaying communication between the terminal device and the external communication network to the communication relay device can be simplified.

1 is a configuration diagram of a mobile communication system according to a first embodiment of the present invention. It is a block diagram of a communication control apparatus and a terminal device. It is explanatory drawing of operation | movement of a mobile communication system. It is explanatory drawing of communication with a terminal device and an external communication network. It is explanatory drawing of operation | movement of the mobile communication system in 2nd Embodiment. It is a block diagram of the mobile communication system in 3rd Embodiment. It is explanatory drawing of operation | movement of the mobile communication system in 3rd Embodiment.

<First Embodiment>
FIG. 1 is a configuration diagram of a mobile communication system 100 according to the first embodiment of the present invention. As illustrated in FIG. 1, the mobile communication system 100 of the first embodiment includes a mobile communication network 10, a terminal device 12, and a communication relay device 14. Note that a plurality of terminal devices 12 are actually included in the mobile communication system 100, but in the following description, attention is paid to any one terminal device 12 for convenience.

  The mobile communication network 10 is a communication network (so-called cellular network) operated by a telecommunications carrier, and provides mobile communication services such as voice communication and data communication to the terminal device 12. As illustrated in FIG. 1, the mobile communication network 10 of the first embodiment includes a communication control device 22 and a radio base station 24. The communication control device 22 is a computer system that controls communication using the mobile communication network 10, and is realized by, for example, an exchange station or a control device that constitutes a core network of the mobile communication network 10.

  The radio base station 24 performs radio communication with the terminal device 12 located in the cell formed by the radio base station 24. For example, the wireless base station 24 is an eNB (evolved Node B) that wirelessly communicates with the terminal device 12 using a communication method compliant with LTE (Long Term Evolution) of 3GPP (Third Generation Partnership Project). Specifically, OFDMA (Orthogonal Frequency Division Multiple Access) is adopted as the downlink radio transmission scheme, and SC-FDMA (Single-Carrier Frequency Division Multiple Access) is adopted as the uplink radio transmission scheme. The terminal device 12 is a portable communication terminal that can be carried by a user, and is a user device (UE: User Equipment) such as a mobile phone or a smartphone. A communication terminal such as a tablet terminal, personal computer, UMPC (Ultra-Mobile Personal Computer), or portable game device can also be used as the terminal device 12.

  As illustrated in FIG. 1, the mobile communication network 10 is connected to an external communication network 18 via a communication relay device 14. The external communication network 18 is a communication network external to the mobile communication system 100, and is typically the Internet.

  The communication relay device 14 is a computer system that relays communication between the mobile communication network 10 and the external communication network 18. That is, the communication relay device 14 functions as a point of interface (POI) between the mobile communication network 10 and the external communication network 18. Specifically, the communication relay device 14 converts, for example, one communication protocol of the mobile communication network 10 and the external communication network 18 to the other communication protocol, and ensures security of communication with the external communication network 18. The terminal device 12 is provided with various specific service functions such as a function for filtering and a filtering function for restricting access to a specific site. That is, the communication relay device 14 can also be expressed as a gateway device or a firewall device. Note that the communication relay device 14 may be an internal element of the mobile communication network 10 (for example, the function of the communication relay device 14 is installed in the communication control device 22).

  The terminal device 12 can communicate with the external communication network 18 via the mobile communication network 10 and the communication relay device 14, and can also communicate with the external communication network 18 via the wireless communication network 16 of FIG. . The wireless communication network 16 is constructed separately from the mobile communication network 10 and is a smaller communication network than the mobile communication network 10. For example, a wireless LAN (for example, Wi-Fi (registered trademark)) compliant with IEEE 802.11 is a typical example of the wireless communication network 16. The wireless communication network 16 can also be referred to as a communication network provided by an operator different from the telecommunications carrier that provides the mobile communication network 10. As illustrated in FIG. 1, the wireless communication network 16 includes a wireless device 162 that performs wireless communication (for example, short-range wireless communication) with the terminal device 12. For example, an access point or a wireless LAN router is used as the wireless device 162.

  When the terminal device 12 is located in a cell formed by the radio base station 24 of the mobile communication network 10, the terminal is connected via the mobile communication network 10 and the communication relay device 14 as illustrated by the arrow Q1 in FIG. The device 12 communicates with the external communication network 18. On the other hand, when the terminal device 12 is located within the communication range of the wireless communication network 16 (that is, a range where communication with the wireless device 162 is possible), the terminal device 12 communicates with the external communication network 18 via the wireless communication network 16. When the terminal device 12 is directly connected to the external communication network 18 from the wireless communication network 16 as indicated by the arrow Q2 in FIG. 1, the communication relay device 14 is not interposed between the terminal device 12 and the external communication network 18. The terminal device 12 cannot use the specific service function of the communication relay device 14. Therefore, in the first embodiment, the terminal device 12 communicates with the external communication network 18 via the wireless communication network 16 and the communication relay device 14 as illustrated by an arrow Q3 in FIG.

  FIG. 2 is a configuration diagram of the communication control device 22 and the terminal device 12. Elements other than the communication control device 22 and the terminal device 12 are omitted in FIG. 2 for convenience. As illustrated in FIG. 2, the communication control device 22 is a computer system including an arithmetic processing device (for example, CPU) 222 and a storage device 224. The storage device 224 stores programs executed by the arithmetic processing device 222 and various data used by the arithmetic processing device 222. The arithmetic processing unit 222 functions as the connection destination designation unit 32 and the connection destination notification unit 34 by executing a program stored in the storage device 224.

  The connection destination designation unit 32 generates connection destination information A that designates the communication relay device 14 as a connection destination of the terminal device 12 at the time of communication using the wireless communication network 16. The connection destination information A is, for example, an IP (Internet Protocol) address of the communication relay device 14. The connection destination notification unit 34 in FIG. 2 transmits the connection destination information A generated by the connection destination specifying unit 32 to the terminal device 12. The connection destination notification unit 34 according to the first embodiment transmits the connection destination information A to the terminal device 12 via the control plane path of the mobile communication network 10. The control plane path is a logical communication path that is established through the interface of the control plane (C-plane) and used for communication of control data, and is a user plane (U-plane) used for communication of user data. ) Differentiated from the route.

  On the other hand, the terminal device 12 is a computer system including an arithmetic processing device (for example, CPU) 122 and a storage device 124 as illustrated in FIG. The storage device 124 stores a program executed by the arithmetic processing device 122 and various data used by the arithmetic processing device 122. The arithmetic processing device 122 functions as the reception processing unit 42 and the communication processing unit 44 by executing a program stored in the storage device 124.

  The reception processing unit 42 receives the connection destination information A transmitted from the connection destination notification unit 34 of the communication control device 22 via the control plane path. The communication processing unit 44 is established via the wireless communication network 16 with the communication relay device 14 specified by the connection destination information A received by the reception processing unit 42, as exemplified by the arrow Q3 in FIG. It communicates with the external communication network 18 via a communication path.

  FIG. 3 is an explanatory diagram of the operation of the mobile communication system 100 according to the first embodiment (parts particularly related to provision of a specific service function). For example, when the power of the terminal device 12 is turned on or when the terminal device 12 moves inside a cell of an arbitrary radio base station 24, a connection request is transmitted from the terminal device 12 to the mobile communication network 10 ( SA1). A series of processes for communication between the mobile communication network 10 and the terminal device 12 is executed upon reception of the connection request (not shown). The connection destination designation unit 32 of the communication control device 22 generates connection destination information A for designating the communication relay device 14 (SA2). As illustrated in FIGS. 3 and 4, the connection destination notifying unit 34 uses the connection destination information A generated by the connection destination specifying unit 32 as the control plane route C established between the request source terminal device 12. Via the terminal device 12 (SA3). The reception processing unit 42 of the terminal device 12 receives the connection destination information A transmitted by the connection destination notification unit 34 via the control plane path C and stores it in the storage device 124 (SA4).

  On the other hand, the terminal device 12 recognizes that it has moved within the communication range of the wireless communication network 16 by receiving a radio wave having a significant intensity from the wireless device 162 of the wireless communication network 16 (SB1). When moving within the communication range of the wireless communication network 16, the communication processing unit 44 of the terminal device 12 establishes a communication path with the communication relay device 14 specified by the connection destination information A received and stored from the communication control device 22. A series of processing (hereinafter referred to as “route establishment processing”) for establishment is executed (SB2). That is, the terminal device 12 is forcibly connected to the communication relay device 14 during communication via the wireless communication network 16.

  Specifically, as illustrated in FIG. 4, a VPN (Virtual Private Network) tunnel T via the wireless communication network 16 is established as a communication path between the terminal device 12 and the communication relay device 14. That is, the terminal device 12 and the communication relay device 14 are VPN-connected via the wireless communication network 16. The VPN tunnel T is a virtual communication path established under a protocol such as IPsec (Security Architecture for Internet Protocol) or L2TP (Layer 2 Tunneling Protocol).

  As illustrated in FIG. 3, the route establishment process SB2 of the first embodiment includes a key exchange SB20. The key exchange SB20 exchanges an encryption key used for encrypting transmission data transmitted and received between the terminal device 12 and the communication relay device 14 between the terminal device 12 and the communication relay device 14 after the communication path is established. It is processing to do.

  When the VPN tunnel T via the wireless communication network 16 is established between the terminal device 12 and the communication relay device 14 by the route establishment process SB2 described above, the communication processing unit 44 of the terminal device 12 Via the external communication network 18 (SB3). That is, the communication processing unit 44 communicates with the external communication network 18 via the communication relay device 14 and the wireless communication network 16 notified from the communication control device 22. Transmission data exchanged between the terminal device 12 and the communication relay device 14 is encrypted using the encryption key assigned to each of the communication relay device 14 and the terminal device 12 in the key exchange SB20 of the route establishment process SB2. Is done. As understood from the above description, in the first embodiment, since the communication relay device 14 is interposed in communication with the external communication network 18 via the wireless communication network 16, the terminal device 12 is provided by the communication relay device 14. The specific service function to be used can be used when communicating with the external communication network 18 via the wireless communication network 16 other than the mobile communication network 10.

  As described above, in the first embodiment, the connection destination information A for designating the communication relay device 14 to which the terminal device 12 should be connected when communicating with the external communication network 18 using the wireless communication network 16 is the mobile communication network. Since the terminal device 12 is notified from the ten communication control devices 22, it is not necessary for the user of the terminal device 12 to specify a connection destination by an operation on the terminal device 12. Therefore, communication with the external communication network 18 via the wireless communication network 16 is performed in comparison with the configuration in which the user designates the connection of the communication relay device 14 and the connection to the communication relay device 14 by operating the terminal device 12. There is an advantage that the procedure for relaying to the relay device 14 is simplified.

  Further, since the connection destination information A is transmitted to the terminal device 12 via the control plane path C of the mobile communication network 10, a configuration in which the communication relay device 14 of the connection destination is notified to the terminal device 12 via the user plane route. As compared with the above, there is an advantage that the intended communication relay device 14 can be notified to the terminal device 12 safely and reliably. In the first embodiment, since the terminal device 12 communicates with the external communication network 18 through the VPN tunnel T established between the communication relay device 14 and the wireless communication network 16, the communication relay device 16 communicates with the wireless communication network 16. There is also an advantage that safety of communication via the device 14 is ensured.

Second Embodiment
A second embodiment of the present invention will be described. Regarding the elements whose functions and operations are the same as those of the first embodiment in each of the embodiments illustrated below, the detailed description of each is appropriately omitted by using the reference numerals used in the description of the first embodiment.

  FIG. 5 is an explanatory diagram of the operation of the mobile communication system 100 in the second embodiment. As illustrated in FIG. 5, when a connection request is received from the terminal device 12 (SA1), the connection destination designating unit 32 of the communication control device 22 generates connection destination information A as in the first embodiment (SA2). . The connection destination notifying unit 34 transmits the encryption key K1 together with the connection destination information A generated by the connection destination designating unit 32 to the requesting terminal device 12 (SA3). The encryption key K1 is an encryption key used for encryption of communication via the VPN tunnel T. The connection destination information A and the encryption key K1 are transmitted from the connection destination notification unit 34 to the terminal device 12 via the control plane path C, and the reception processing unit 42 of the terminal device 12 transmits the connection destination information A via the control plane path C. Then, the encryption key K1 is received and stored (SA4). Further, the connection destination notification unit 34 transmits the encryption key K2 corresponding to the encryption key K1 to the communication relay device 14 via the control plane path C (SA5). The encryption key K2 is, for example, an encryption key generated by a predetermined operation on the encryption key K1 (or an encryption key that is common with the encryption key K1).

  As described above, the encryption key K1 is transmitted from the communication control device 22 to the terminal device 12 before the path establishment process SB2 for establishing the VPN tunnel T between the terminal device 12 and the communication relay device 14 is performed. The encryption key K 2 is transmitted from the communication control device 22 to the communication relay device 14. Therefore, in the second embodiment, the key exchange SB20 described in the first embodiment is omitted from the path establishment process SB2. Transmission data exchanged between the terminal device 12 and the communication relay device 14 via the VPN tunnel T uses the encryption key K1 assigned to the terminal device 12 and the encryption key K2 assigned to the communication relay device 14. And encrypted. That is, the communication processing unit 44 of the terminal device 12 encrypts communication with the communication relay device 14 via the VPN tunnel T using the encryption key K1.

  In the second embodiment, the same effect as in the first embodiment is realized. In the second embodiment, since the encryption key K (K1, K2) is assigned to the terminal device 12 and the communication relay device 14 via the control plane route C of the mobile communication network 10, the route establishment process SB2 The key exchange SB20 is omitted. Therefore, the above-mentioned effect that the procedure (route establishment process SB2) for relaying communication with the external communication network 18 via the wireless communication network 16 to the communication relay device 14 is simplified is particularly remarkable. Further, since the control plane path C is used for transmitting the encryption key K, there is an advantage that the encryption key K can be safely given to the terminal device 12 and the communication relay device 14 while avoiding dangers such as leakage.

<Third Embodiment>
FIG. 6 is a configuration diagram of the mobile communication system 100 according to the third embodiment. As illustrated in FIG. 6, the mobile communication network 10 of the third embodiment includes a registration device 26 in addition to the communication control device 22 and the radio base station 24 similar to those of the first embodiment. The registration device 26 is a database that holds and manages the contract information S in which the content of the mobile communication service contract is registered for each terminal device 12. The contract information S of the third embodiment designates for each terminal device 12 whether or not there is a usage contract for the specific service function provided by the communication relay device 14. In FIG. 6, the registration device 26 is illustrated as an apparatus separate from the communication control device 22, but the function of the registration device 26 may be mounted on the communication control device 22.

  FIG. 7 is an explanatory diagram of the operation of the mobile communication system 100 in the third embodiment. As illustrated in FIG. 7, when a connection request is received from the terminal device 12 (SA1), the connection destination designating unit 32 of the communication control device 22 refers to the contract information S managed by the registration device 26, thereby requesting the request source. It is determined whether or not there is a usage contract for the specific service function for the terminal device 12 (SC). When there is a usage contract for the specific service function (SC: YES), as in the first embodiment, the connection destination information A that specifies the communication relay device 14 is sent from the connection destination notification unit 34 via the control plane path C. (SA2 to SA4). When the terminal device 12 moves within the communication range of the wireless communication network 16, the terminal device 12 establishes a VPN tunnel T via the wireless communication network 16 with the communication relay device 14 specified by the connection destination information A (route establishment processing). SB2), and communicates with the external communication network 18 through the VPN tunnel T (SB3).

  On the other hand, when there is no usage contract for the specific service function, transmission of the connection destination information A from the communication control device 22 to the terminal device 12 (notification of the communication relay device 14) is not executed. Therefore, the terminal device 12 that has moved within the communication range of the wireless communication network 16 passes through a communication path that reaches the external communication network 18 directly from the wireless communication network 16 (that is, without interposing the communication relay device 14). It communicates with the external communication network 18. That is, the communication relay device 14 does not relay communication between the terminal device 12 and the external communication network 18. Therefore, the terminal device 12 cannot use the specific service function. As will be understood from the above description, the connection destination notification unit 34 of the third embodiment is configured to include a plurality of terminal devices 12 that can perform mobile communication using the mobile communication network 10 (that is, subscribers of mobile communication services). The connection destination information A is transmitted to the terminal device 12 in which the usage contract for the specific service function is registered in the contract information S among the terminal devices 12).

  In the third embodiment, the same effect as in the first embodiment is realized. Further, according to the third embodiment, the contract information S indicates whether the communication relay device 14 is interposed during communication with the external communication network 18 via the wireless communication network 16 (whether the specific service function is applied). There is also an advantage that it can be selected depending on For example, assuming that a filtering function that restricts access to a specific site is a specific service function, the use of the specific service function is concluded for the terminal device 12 that is assumed to be used by minors such as elementary school students and junior high school students. The filtering function can be effectively applied even when the terminal device 12 communicates with the external communication network 18 via the wireless communication network 16. In the above description, the third embodiment is illustrated based on the first embodiment. However, the second embodiment and the third embodiment can be combined.

<Modification>
Each of the above-described embodiments can be variously modified. Specific modifications are exemplified below. Two or more aspects arbitrarily selected from the following examples can be appropriately combined as long as they do not contradict each other.

(1) In each of the above-described embodiments, the connection destination information A is transmitted to the terminal device 12 in response to a connection request from the terminal device 12, but the time point at which the connection destination information A is transmitted to the terminal device 12 is limited to the above examples. Not. For example, the connection destination information A can be transmitted from the communication control device 22 to the terminal device 12 every time the terminal device 12 moves into the communication range of the wireless communication network 16. The same applies to the encryption key K (K1, K2), and the trigger for transmission to the terminal device 12 and the communication relay device 14 is arbitrary.

(2) In the above-described embodiments, the configuration in which the communication control device 22 is included in the core network of the mobile communication network 10 has been exemplified. However, the position where the communication control device 22 is installed in the mobile communication network 10 is as described above. It is not limited to the illustration. For example, the communication control device 22 can be mounted on the radio base station 24.

(3) Each function (connection destination designating unit 32, connection destination notifying unit 34) of the communication control device 22 may be realized by an electronic circuit such as an FPGA (Field Programmable Gate Array) or a DSP (Digital Signal Processor). Similarly, each function (reception processing unit 42 and communication processing unit 44) of the terminal device 12 can be realized by an electronic circuit such as an FPGA or a DSP.

(4) As described above, the communication control device 22 of each embodiment described above can be realized by the cooperation of a computer (arithmetic processing device 222) and a program. The program according to a preferred aspect causes the computer to function as the connection destination designation unit 32 and the connection destination notification unit 34. Similarly, the terminal device 12 of each embodiment described above can be realized by the cooperation of a computer (arithmetic processing device 122) and a program as illustrated above. The program according to a preferred aspect causes a computer to function as the reception processing unit 42 and the communication processing unit 44. The program according to each aspect described above can be provided in a form stored in a computer-readable recording medium and installed in the computer. The recording medium is, for example, a non-transitory recording medium, and an optical recording medium such as a CD-ROM is a good example, but a known arbitrary format such as a semiconductor recording medium or a magnetic recording medium is used. A recording medium may be included. It is also possible to provide the aforementioned program in the form of distribution via a communication network and install it on a computer.

DESCRIPTION OF SYMBOLS 100 ... Mobile communication system, 10 ... Mobile communication network, 12 ... Terminal device, 122, 222 ... Arithmetic processing device, 124, 224 ... Storage device, 14 ... Communication relay device, 16 ... Wireless Communication network, 162... Wireless device, 18... External communication network, 22... Communication control device, 24 ....... wireless base station, 26... Registration device, 32. , 42... Reception processing unit, 44... Communication processing unit.

Claims (7)

A communication control device in a mobile communication network connected to an external communication network via a communication relay device,
A connection destination designating unit that generates connection destination information for designating the communication relay device as a connection destination of the terminal device when the terminal device communicates with the external communication network using a wireless communication network other than the mobile communication network When,
A communication control device comprising: a connection destination notifying unit that transmits the connection destination information to the terminal device via a control plane path of the mobile communication network. The connection destination notification unit transmits an encryption key used for encryption of communication between the terminal device and the communication relay device via the wireless communication network to the terminal device via the control plane path. The communication control device according to claim 1. The connection destination notifying unit is provided for a terminal device in which a use contract for a service provided by the communication relay device is registered in contract information among a plurality of terminal devices capable of mobile communication using the mobile communication network. The communication control device according to claim 1 or 2, wherein the connection destination information is transmitted. A terminal device capable of communication using a mobile communication network connected to an external communication network via a communication relay device,
When connecting to the external communication network using a wireless communication network other than the mobile communication network, connection destination information for designating the communication relay device as a connection destination of the terminal device is used as a control plane of the mobile communication network. A reception processing unit for receiving via a route;
A terminal device comprising: a communication processing unit that communicates with the external communication network via a communication path established via the wireless communication network with the communication relay device specified by the connection destination information. The terminal device according to claim 4, wherein the communication processing unit communicates with the external communication network via a VPN tunnel established with the communication relay device via the wireless communication network. The reception processing unit receives an encryption key used for encryption of communication with the communication relay device via the wireless communication network via the control plane path,
The terminal device according to claim 4, wherein the communication processing unit encrypts communication with the communication relay device via the wireless communication network using an encryption key received by the reception processing unit. A mobile communication system comprising a mobile communication network connected to an external communication network via a communication relay device, and a terminal device capable of communication using the mobile communication network,
The mobile communication network is
A connection destination designating unit that generates connection destination information for designating the communication relay device as a connection destination of the terminal device when the terminal device communicates with the external communication network using a wireless communication network other than the mobile communication network When,
A connection destination notification unit that transmits the connection destination information to the terminal device via a control plane path of the mobile communication network,
The terminal device
A reception processing unit that receives the connection destination information via the control plane path;
A mobile communication system, comprising: a communication processing unit that communicates with the external communication network via a communication path established with the communication relay device specified by the connection destination information via the wireless communication network.

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