COMMUNICATION SYSTEM, TERMINAL, AND COMMUNICATION CONTROL METHOD

Abstract

To provide a communication system that can prevent terminals capable of connecting to a plurality of networks including a 3GPP network or a non-3GPP network from becoming unable to communicate or causing an excessive communication load.SOLUTION: In a communication system including a server, the server is disposed in a 3GPP network or a non-3GPP network and transmits network identification information for identifying a communication destination network to a terminal based on communication destination identification information that identifies a communication destination of the terminal capable of communication in both 3GPP network and non-3GPP network.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a communication system, a terminal, and a communication control method. [Background technology]

[0002] Conventionally, in an LTE communication system, an enhanced Packet Data Gateway (ePDG) is known as a component for accommodating a non-3GPP terminal performing non-3GPP (Third Generation Partnership Project) wireless access in an evolved packet core (EPC) (see non-patent documents 1 and 2). That is, the ePDG operates as a gateway to which a mobile terminal connects when accommodating untrusted non-3GPP wireless access (untrusted non-3GPP IP access) that is unreliable in terms of security, such as a public wireless local area network (LAN). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] “3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Architecture enhancements for non-3GPP accesses (Release 15)”, 3GPP TS 23.402 V15.0.0 (217-06), P30-P31 [Non-Patent Document 2] Takehiro Nakamura and 5 others, "Activities and Contributions in Finalizing 3GPP LTE / SAE Standard Specifications," NTT DOCOMO Technical Journal Vol.17 No.2, P36-P45 Summary of the Invention [Problem to be solved by the invention]

[0004] In the 3GPP network, it is not assumed that a non-3GPP terminal accommodated in the 3GPP network and a 3GPP terminal placed in the 3GPP network belong to any of the multiple networks, which are the 3GPP network and the non-3GPP network. Therefore, neither the non-3GPP terminal nor the 3GPP terminal can selectively control the network (communication path) according to the communication destination. Therefore, communication data communicated by the non-3GPP terminal and the 3GPP terminal may be sent to one of the multiple networks, causing a communication failure event in which communication is impossible or an excessive communication load.

[0005] Here, a communication load phenomenon will be described. For example, it is assumed that the use of a non-3GPP network (for example, a wireless LAN) in which a router or the like is arranged is set to be prioritized over the use of a 3GPP network in which an EPC device is arranged. In this case, communication data from a terminal (3GPP terminal or non-3GPP terminal) that is not connected to the non-3GPP network and is connected to the 3GPP network does not reach a communication destination (for example, a server corresponding to a website address). This is because even if the terminal is capable of communicating via both the non-3GPP network and the 3GPP network, it does not communicate via either of the networks (here, the 3GPP network). In this case, for example, even if the system is capable of accommodating a non-3GPP terminal in the 3GPP network, the advantage cannot be fully utilized.

[0006] Next, the occurrence of an excessive communication load will be described. For example, assume that the use of a 3GPP network in which an EPC device is located is set to be prioritized over the use of a non-3GPP network in which a router or the like is located. In this case, even if a communication destination (e.g., a server) can be reached via a non-3GPP network, communication via the 3GPP network in which the EPC device is located is selected. Therefore, even if the communication load in the non-3GPP network is smaller than the communication load in the 3GPP network, for example, an excessive communication load occurs when a terminal communicates via the 3GPP network instead of the non-3GPP network.

[0007] The present invention has been made in consideration of the above-mentioned conventional situation, and provides a communication system, a terminal, and a communication control method that can prevent a terminal connectable to multiple networks, including a 3GPP network or a non-3GPP network, from becoming unable to communicate or from experiencing excessive communication load. [Means for solving the problem]

[0008] One aspect of the present invention is a communication system including a server, the server being disposed in a 3GPP network or a non-3GPP network, acquiring communication destination identification information for identifying a communication destination of a terminal capable of communicating in both the 3GPP network and the non-3GPP network, and identifying the network of the communication destination based on the route identification information. Contains IP address and netmask information A communication system that transmits network identification information to the terminal.

[0009] One aspect of the present invention is a terminal capable of communicating in both a 3GPP network and a non-3GPP network, the terminal comprising a communication unit and a processing unit, the communication unit being a server disposed in the 3GPP network or the non-3GPP network, and identifying the destination network based on destination identification information that identifies the destination of the terminal. Contains IP address and netmask informationThe terminal receives network identification information from a server that transmits the network identification information, and the processing unit stores communication control information, including the network identification information, for communicating with the communication destination in a table.

[0010] One aspect of the present invention is a communication control method in a server disposed in a 3GPP network or a non-3GPP network, the method comprising: acquiring communication destination identification information for identifying a communication destination of a terminal capable of communicating in both the 3GPP network and the non-3GPP network; and identifying the communication destination network based on the route identification information. Contains IP address and netmask information A communication control method includes transmitting network identification information to the terminal.

[0011] One aspect of the present invention is a communication control method in a terminal capable of communicating in both a 3GPP network and a non-3GPP network, the method comprising: a server disposed in the 3GPP network or the non-3GPP network, the server identifying the destination network based on destination identification information identifying the destination of the terminal; Contains IP address and netmask information The communication control method includes receiving network identification information from a server that transmits the network identification information, and storing communication control information including the network identification information and for communicating with the communication destination in a table. Effect of the Invention

[0012] According to the present invention, it is possible to prevent a terminal connectable to a plurality of networks including a 3GPP network or a non-3GPP network from becoming unable to communicate or from being subjected to an excessive communication load. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a block diagram showing a configuration example of a communication system including a non-3GPP terminal according to a first embodiment; [Diagram 2] A diagram showing an example of information stored in a DNS server database. [Diagram 3]Diagram showing the initial state of the routing table [Figure 4] A diagram showing the state in which individual communication control information for communication destinations is registered in the routing table. [Diagram 5] FIG. 2 is a sequence diagram showing an example of the operation of the communication system shown in FIG. [Figure 6] A block diagram showing a first example of a DNS server arrangement in a communication system. [Figure 7] FIG. 7 is a sequence diagram showing a first operation example of the communication system shown in FIG. [Figure 8] FIG. 7 is a sequence diagram showing a second operation example of the communication system shown in FIG. [Figure 9] A block diagram showing a second example of a DNS server arrangement in a communication system. [Figure 10] FIG. 10 is a sequence diagram showing a first operation example of the communication system shown in FIG. [Figure 11] FIG. 10 is a sequence diagram showing a second operation example of the communication system shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0015] (First embodiment) FIG. 1 is a diagram showing a first configuration example of a communication system 5 in the first embodiment. The communication system 5 includes a terminal 10, a gateway 30, an EPC device 50, a router 60, and a DNS (Domain Name System) server 70. The terminal 10 includes a processing unit 11, a storage unit 12, a communication unit 13, an operation unit 14, and a display unit 15. The gateway 30 includes a processing unit 31, a storage unit 32, and a communication unit 33. The EPC device 50 includes a PGW (Packet data network GateWay) 51, an SGW (Serving Gateway) 53, an MME (Mobility Management Entity) 54, and an HSS (Home Subscriber Server) 55. The DNS server 70 includes a processing unit 71, a storage unit 72, and a communication unit 73. The communication system 5 accommodates a non-3GPP terminal in a 3GPP network.

[0016] The terminal 10 includes at least one of the terminal 10A and the terminal 10B. The terminal 10A is a terminal that does not comply with the 3GPP standard (non-3GPP terminal). The terminal 10B is a terminal that complies with the 3GPP standard (3GPP terminal). The terminal 10 is owned by a user. There may be a plurality of terminals 10.

[0017] The terminal 10A communicates with the gateway 30A via a non-3GPP network N1. The non-3GPP network N1 is a network that does not comply with the 3GPP standard and may include a LAN (e.g., a wireless LAN, a wired LAN), the Internet, and the like. The non-3GPP terminal may be a terminal that communicates with other communication devices at least via the non-3GPP network N1. In addition, the non-3GPP terminal has a function of communicating with other communication devices via the 3GPP network N2 with the assistance of communication control by the gateway 30.

[0018] The terminal 10B communicates with the gateway 30B via a 3GPP network N2. The 3GPP network N2 is a network that complies with the 3GPP standard and may include, for example, an LTE network and a mobile phone network. The 3GPP terminal communicates with other communication devices at least via the 3GPP network N2. The 3GPP terminal also has a function of communicating with other communication devices via a non-3GPP network N1.

[0019] The processing unit 11 of the terminal 10 realizes various functions by a processor (for example, a CPU (Central Processing Unit)) executing a program stored in the storage unit 12. The processing unit 11 controls the operation of each unit of the terminal 10.

[0020] The storage unit 12 of the terminal 10 may have, for example, a read only memory (ROM), a random access memory (RAM), or various storages (for example, a hard disk drive (HDD), a solid state drive (SSD)), and holds various information, data, programs, and tables. The table has a routing table for the terminal 10 to communicate with other communication devices. The routing table will be described in detail later.

[0021] The communication unit 13 of the terminal 10 communicates with other communication devices via the non-3GPP network N1. The communication unit 13 can communicate with, for example, the gateway 30, the router 60, the DNS server 70, and the like. The communication unit 13 of the terminal 10A can communicate with other communication devices via the 3GPP network N2 with the assistance of communication in the 3GPP network N2 by the gateway 30A. The communication unit 13 of the terminal 10A can communicate with other communication devices via the non-3GPP network N1. The communication unit 13 of the terminal 10B can communicate with other communication devices via the 3GPP network N2. The communication unit 13 of the terminal 10B can communicate with other communication devices via the non-3GPP network N1.

[0022] The operation unit 14 of the terminal 10 accepts various operations by the terminal 10. The operation unit 14 may be, for example, an input key, a button, a touch panel, a microphone, etc. The display unit 15 of the terminal 10 displays various data. The display unit 15 may be, for example, a liquid crystal display.

[0023] The gateway 30 manages the terminals 10 under the gateway 30, and relays communication between the terminals 10 and the EPC device 50. Each gateway 30 may manage a plurality of terminals 10 under its control. A plurality of gateways 30 may be deployed. The gateways 30 may be installed, for example, outdoors, or in each building. The gateways 30 may be numerically and geographically distributed. One or more terminals 10 may be present under each of the plurality of gateways 30.

[0024] The gateway 30 includes at least one of a gateway 30A and a gateway 30B. One or more terminals 10A may be present under the gateway 30A. One or more terminals 10B may be present under the gateway 30B.

[0025] The gateway 30B operates as an eNB (eNodeB) serving as a base station device. Description of the configuration and operation of well-known parts of the gateway 30B will be omitted or simplified.

[0026] The gateway 30A operates as a base station that accommodates the terminal 10A under the gateway 30A in the EPC device 50 for LTE communication. The gateway 30A may have some of the functions of the ePDG. However, unlike the ePDG, the gateway 30A is not directly connected to the PGW 51 and HSS 55 of the EPC device 50, and cooperates with the MME 54 and SGW 53 of the EPC device 50 to realize functions such as relaying control data and user data.

[0027] The gateway 30A has at least a function of communicating with a non-3GPP terminal. The gateway 30A may have a function of communicating with a 3GPP terminal. The gateway 30B has at least a function of communicating with a 3GPP terminal. The gateway 30B may have a function of communicating with a non-3GPP terminal.

[0028] The interface between the gateway 30A and the EPC device 50 may be the same S1 interface as that used when accommodating an eNB as a general base station in an LTE communication system. In this case, an interface that omits messages related to handover of S1AP (S1 Application Protocol) from among the messages that the S1 interface has can be used. The interface between the gateway 30B and the EPC device 50 uses the S1 interface.

[0029] The gateway 30A performs relay processing of data related to communication in the non-3GPP network N1 on the terminal 10A side and communication in the 3GPP network N2 on the EPC device 50 side. The gateway 30B performs relay processing of data related to communication in the 3GPP network N2 on the terminal 10B side and communication in the 3GPP network N2 on the EPC device 50 side.

[0030] The gateway 30 relays communication data (e.g., control data or user data) from the terminal 10 to the SGW 53, PGW 51, SGi (a network above the EPC), etc., or relays communication data from the SGW 53, PGW 51, SGi to the terminal 10. In this case, the gateway 30 may relay control data between the terminal 10 and the MME 54. The gateway 30 may also relay user data between the terminal 10 and the SGW 53.

[0031] The processing unit 31 of the gateway 30 realizes various functions by a processor (e.g., a CPU (Central Processing Unit)) executing a program stored in the storage unit 32. The processing unit 31 controls the operation of each unit of the gateway 30. The processing unit 31 relays control data and user data via the communication unit 33.

[0032] The memory unit 32 of the gateway 30 may include, for example, a read only memory (ROM), a random access memory (RAM), or various storage devices (for example, a hard disk drive (HDD), a solid state drive (SSD)), and holds various information, data, and programs.

[0033] The communication unit 33 of the gateway 30 communicates with the terminal 10 and the EPC device 50 (wired communication or wireless communication).

[0034] The EPC device 50 is a device disposed in an LTE core network, and communicates with the gateway 30 according to the LTE protocol. Each node of the EPC device 50, the PGW 51, the SGW 53, the MME 54, and the HSS 55, may be a logical node or a physical node. That is, the functions may be aggregated in one device (server), or the functions may be distributed to a plurality of individual devices (servers). The EPC device 50 may also include a PCRF (Policy and Charging Rule Function) node. Note that the EPC device 50 is not limited to this configuration, and may include other associated elements.

[0035] The MME 54 and the HSS 55, together with the PCRF, process C-plane data, which is control data. The SGW 53 and the PGW 51 process U-plane data, which is user data. Thus, for example, U-plane data from an external network (upstream of the EPC device 50) to the terminal 10, that is, U-plane traffic, reaches the EPC device 50 from the external network and is transmitted to the terminal 10 via the PGW 51, the SGW 53, and the gateway 30.

[0036] The MME 54 is a node that provides mobility control and performs mobility control such as location registration, paging, and handover.

[0037] The HSS 55 is a node having a subscriber management database in LTE, and manages subscriber contract information, authentication information, location information, etc. The MME 54 performs user authentication based on the authentication information notified from the HSS 55.

[0038] The SGW 53 is a gateway that is connected to the gateway 30, accommodates non-3GPP access, and transmits data to the terminal 10 and the PGW 51.

[0039] The PGW 51 is a gateway that assigns IP addresses to the terminal 10 and transfers packets at a connection point with an external network (PDN). The PGW 51 may operate in cooperation with a PCRF in accordance with a policy (policy control information) held by the PCRF. The PGW 51 may control the amount and speed of communication communicated through each bearer in accordance with the policy held by the PCRF.

[0040] Furthermore, the PGW 51 cooperates with the MME 54 to establish or delete a bearer (a data communication path).

[0041] The PCRF is a node that controls the QoS (Quality of Service; control of communication quality, such as priority packet transfer) of user data transfer and for billing. The QoS value determined by the PCRF is notified to the PGW 51. The PGW 51 performs QoS control on U-plane data according to the notified QoS value. The QoS value may be, for example, a setting value included in the control information of a policy.

[0042] The EPC device 50 has a processing unit, a storage unit, and a communication unit. When each node of the EPC device 50 is a logical node, the processing unit, the storage unit, and the communication unit may be provided in one device. When each node of the EPC device 50 is a physical node, the processing unit, the storage unit, and the communication unit may be provided in each node.

[0043] The processing unit of the EPC device 50 realizes various functions by a processor (e.g., a CPU) executing a program stored in the memory unit. The memory unit of the EPC device 50 may have, for example, a ROM, a RAM, or various storages (e.g., an HDD, an SSD), and stores various information, data, and programs. The communication unit of the EPC device 50 communicates (wired communication or wireless communication) with the gateway 30 and various devices in an external network. The communication by the EPC device 50 includes LTE communication. The LTE communication may include VoLTE communication.

[0044] The router 60 is disposed in the non-3GPP network N1 and relays communications in the non-3GPP network N1.

[0045] The DNS server 70 has a database that holds name information such as host names and domain names in association with entity information such as IP addresses. The DNS server 70 receives name information such as an APN (Access Point Name) from a communication device, and provides entity information such as information related to IP addresses from this name information to the communication device. The entity information includes network identification information that identifies networks to which various communication destinations belong.

[0046] The network identification information is made up of a set of IP network identifiers, and may include IP address and netmask information. The IP address and netmask together define an address range that includes multiple IP addresses. The address range includes a single IP address identified by the APN.

[0047] The communication unit 73 of the DNS server 70 communicates (wired communication or wireless communication) with the terminal 10 and the EPC device 50. The communication unit 73, for example, receives communication destination identification information (e.g., APN) for identifying a communication destination of the terminal 10 and transmits network identification information.

[0048] The storage unit 72 of the DNS server 70 may have, for example, a ROM, a RAM, or various storages (for example, a HDD, an SSD), and stores various information, data, programs, and the above database. The database may store the APN and the network identification information. The database may store the network identification information in a text record (TXT record) among the resource records. The network identification information may indicate an IP address range including a plurality of specific IP addresses. The network identification information may be information such as "192.0.2.0 255.255.255.0", "198.51.100.0 / 24", etc. The DNS server 70 can search for and provide the network identification information corresponding to the communication destination identification information by previously storing the communication destination identification information and the network identification information in association with each other in the database.

[0049] The processing unit 71 of the DNS server 70 realizes various functions by a processor (e.g., a CPU) executing a program stored in the storage unit 72. The processing unit 71 controls the operation of each unit of the DNS server 70. The processing unit 71 may, for example, refer to a database, extract network identification information corresponding to communication destination identification information, and provide it via the communication unit 73.

[0050] In addition, in Fig. 1, the DNS server 70 is located at an arbitrary position. In order to show that the DNS server 70 is located at an arbitrary position, the specific connection relationship between the DNS server 70 and other devices is not clearly shown in Fig. 1. Communication between the DNS server 70 and the terminal 10 is performed using, for example, IP packets.

[0051] FIG. 2 is a diagram showing an example of information stored in the database DB of the DNS server 70. In FIG. 2, the database DB stores an APN in association with network identification information. The APN is described in a fully qualified domain name (FQDN) format, that is, a domain name format. The network identification information includes an IP address corresponding to the APN and information on its netmask. Note that both the entire APN (full name) and a part of it (abbreviation) are described in the FQDN format. For example, the entire APN is represented as "example1.jp.mncxxx.mccyyy.3gppnetwork.org" and a part of the APN is represented as "example1.jp". Here, the part of the APN as shown in FIG. 2 will be mainly described as the APN, but the same applies to the entire APN.

[0052] Next, routing by the communication system 5 will be described.

[0053] The terminal 10 refers to the routing table to communicate communication data to other communication devices. The routing table holds communication control information for the terminal 10 to communicate with one or more candidate communication destinations (candidate communication destinations). The candidate communication destinations are intended to be potential communication destinations of the actual terminal 10. One of the candidate communication destinations will be the actual communication destination of the terminal 10.

[0054] The communication control information is held for each communication destination candidate. The routing table includes, as the communication control information, information such as a network destination, a netmask, a gateway, an interface, and a metric.

[0055] The network destination indicates the IP address of the destination network (candidate communication destination). The netmask indicates the subnet mask of the destination network. The gateway indicates the IP address of the gateway (next hop communication device). The interface indicates the IP address of the interface that sends out the IP packet. The interface may include, for example, a wireless LAN (non-3GPP), a wired LAN (non-3GPP), and an interface for a public line (3GPP). The metric is a metric value that indicates the priority for selecting a network. When there are multiple networks defined by the destination network and the netmask, the communication unit 13 selects the network with the smallest metric value and communicates with it.

[0056] The communication unit 13 communicates with the communication destination based on the communication control information held in the routing table. When the routing table contains communication control information (individual communication control information) including network identification information (individual network identification information) corresponding to an address range including the IP address of the communication destination of the terminal 10, the communication unit 13 communicates with the communication destination according to the individual communication control information. When the routing table does not contain individual communication control information of the communication destination, the communication unit 13 communicates according to the communication control information of the default route held in the routing table.

[0057] For example, the default route is indicated by a network destination of "0.0.0.0" and a netmask of "0.0.0.0". When multiple default routes are stored in the routing table, the communication unit 13 selects the route (network) with the smallest metric value. That is, the communication unit 13 communicates with the communication destination according to the communication control information of the default route with the smallest metric value. In this case, the same single route is selected without considering the placement position of the communication destination on the network and without considering the communication load in each network, so that a route with a high communication load or a route that does not allow communication data to reach the communication destination may be selected.

[0058] The communication unit 13 may acquire individual network identification information of the communication destination from the DNS server 70. The processing unit 11 may add the communication control information including the individual network identification information of the communication destination to the routing table and store it. The gateway information in the communication control information is determined based on the individual network identification information of the communication destination. The interface information in the communication control information may be set to one of the interfaces with which the terminal 10 can communicate, and may be specified via the operation unit 14, for example, or one of the interfaces held by the terminal 10 may be automatically specified. The metric information in the communication control information may be specified via the operation unit 14.

[0059] As a result, even if individual communication control information of a communication destination is not registered in the routing table at first, the terminal 10 can communicate according to the specific communication control information of the additionally registered communication destination, not the communication control information of the default route. Therefore, the terminal 10 can specify a route with a low communication load or a network that allows communication data to reach the communication destination, according to the registered communication control information.

[0060] The method of acquiring the network identification information of the communication destination by the terminal 10 is arbitrary. For example, the terminal 10 may acquire the network identification information of the communication destination corresponding to the APN from the DNS server 70. The APN may be used as identification information for identifying an external network to which a bearer for the terminal 10 to communicate is connected. In the case of the same APN, the bearer is connected to a communication destination of the same external network. The APN may be determined when the bearer is established.

[0061] FIG. 3 is a diagram showing the initial state (first state) of the routing table TB. In the first state, individual communication control information of the communication destination is not registered. Therefore, when communication with the communication destination is attempted in the first state, communication is performed according to the default route registered in the routing table TB. For example, the two default routes shown in FIG. 3 have metrics of 50 and 100, and the smaller value of 50 is prioritized. In this case, for example, the non-3GPP network N1 in which the router 60 exists is prioritized, and the 3GPP network N2 as a mobile network is not used. In this case, the terminal 10 cannot enjoy services that are provided only through communication via a mobile network, for example. Note that interface information is omitted from FIG. 3.

[0062] FIG. 4 is a diagram showing a state (second state) in which individual communication control information of a communication destination is registered in the routing table TB. In the second state, the terminal 10 communicates according to the individual communication control information CC1 of the registered communication destination. The individual communication control information CC1 of the communication destination can be set based on the acquired network identification information, information specified by the user via the operation unit 14, or information held by the terminal 10. Thus, by setting the terminal 10 to use the 3GPP network N2 for communication with the communication destination, for example, the terminal 10 can communicate with the communication destination via the 3GPP network N2 and enjoy services provided only for communication via the 3GPP network N2. Note that interface information is omitted from FIG. 4.

[0063] In this way, the communication system 5 can use a routing table to manage which network a packet is to be sent to depending on the communication destination of the terminal 10. The communication system 5 can appropriately control routes in multiple networks that the terminal 10 can use by appropriately rewriting the information in the routing table. For example, the terminal 10 can use a desired network (e.g., 3GPP network N2) in accordance with a longest match by registering individual communication control information CC1 of the communication destination in the routing table.

[0064] FIG. 5 is a sequence diagram showing an example of the operation of the communication system 5. As shown in FIG.

[0065] It is assumed that individual communication control information of the communication destination is not held in the routing table at the start of the process in Fig. 5. It is also assumed that, as an example, at the start of the process in Fig. 5, the non-3GPP network N1 is set to be selected with priority over the 3GPP network N2 according to communication control information of a default route held in the routing table.

[0066] The PGW 51 of the EPC device 50 establishes a bearer with the terminal 10 via the gateway 30 (S11). The PGW 51 assigns an IP address to the terminal 10 corresponding to the bearer, and determines an APN corresponding to the communication destination of the external network to which the bearer is connected (S11). The APN information is shared between the EPC device 50 and the terminal 10, and is held in each memory unit.

[0067] The processing unit 11 of the terminal 10 acquires information on the APN corresponding to the bearer shared with the EPC device 50 (S12). The processing unit 11 transmits the information on the APN to the DNS server 70 via the communication unit 13, and inquires about network identification information of the communication destination (S13).

[0068] The communication unit 73 of the DNS server 70 acquires the information of the APN. The processing unit 71 refers to the database, extracts the network identification information of the communication destination corresponding to the APN, and notifies the terminal 10 via the communication unit 73 (S14). This network identification information corresponds to, for example, information that the terminal 10 transmits to the 3GPP network N2.

[0069] The communication unit 13 of the terminal 10 receives the destination network identification information from the DNS server 70 (S15). The processing unit 11 registers the communication control information CC1 including the destination network identification information in the routing table (S15).

[0070] In the communication system 5, when a bearer related to the terminal 10 is established, an APN corresponding to the communication destination of the terminal 10 is determined. The processing unit 11 of the terminal 10 inquires of the DNS server 70, via the communication unit 13, about network identification information of the communication destination for transmission to, for example, the 3GPP network N2, based on the determined APN. The processing unit 71 of the DNS server 70 refers to a database, extracts network identification information corresponding to the APN, and responds to the inquiry using a TXT record via the communication unit 73. The processing unit 11 of the terminal 10 adds communication control information CC1 including network identification information of the communication destination for transmission to, for example, the 3GPP network N2, to the routing table, based on the information described in the TXT record from the DNS server 70.

[0071] As a result, the communication system 5 can newly register the individual communication control information CC1 of the communication destination in the routing table, and can communicate using the communication control information CC1 without needing to communicate using a default route. In other words, the DNS server 70 can provide the terminal 10, which can communicate in both the non-3GPP network N1 and the 3GPP network N2, with network identification information for optimally controlling the network to be used for transmission depending on the communication destination. The terminal 10 can register the communication control information CC1 in the routing table based on the provided network identification information, and can select the optimal network. Therefore, the communication system 5 can prevent communication with the communication destination from becoming impossible or communication efficiency from becoming low.

[0072] Also, the function of the DNS server 70 is to respond with an IP address based on information in FQDN format, which is the description format of the APN. Therefore, it is easy to use a combination of the APN and DNS. Thus, the DNS server 70 provides the network identification information of the communication destination based on the APN, and the communication system 5 can improve the efficiency of providing the network identification information of the communication destination. Note that the network identification information of the communication destination for the APN may be provided to the terminal 10 by something other than the DNS server 70.

[0073] (First example of DNS server placement) Next, a first specific example of the arrangement of the DNS server 70 is shown. Fig. 6 is a block diagram showing the first example of the arrangement of the DNS server 70 in the communication system 5. In the communication system 5A1, which is the communication system 5 taking into account the first example of the arrangement of the DNS server 70, the same components as those in the communication system 5 shown in Fig. 1 are given the same reference numerals, and the description thereof will be omitted or simplified. In the communication system 5A1, the DNS server 70 is arranged in a higher-level network of the EPC device 50.

[0074] Fig. 7 is a sequence diagram showing a first operation example of the communication system 5A1, in which the priority of the network selection is taken into consideration.

[0075] It is assumed that individual communication control information of the communication destination is not held in the routing table at the start of the process of Fig. 7. It is also assumed that, as an example, the non-3GPP network N1 is set to be selected preferentially over the 3GPP network N2 according to communication control information of a default route held in the routing table at the start of the process of Fig. 7. It is also assumed that individual communication control information for communicating with the DNS server 70 is not registered in the routing table at the start of the process of Fig. 7.

[0076] First, the PGW 51 of the EPC device 50 establishes a bearer with the terminal 10 via the gateway 30 (S21). The PGW 51 assigns an IP address to the terminal 10 corresponding to the bearer, and determines an APN corresponding to a communication destination of an external network to which the bearer is connected (S21). Information on the APN is shared between the EPC device 50 and the terminal 10, and is held in each memory unit. In addition, the PGW 51 determines a DNS server 70 arranged in an upper network of the EPC device 50 as a server for obtaining network identification information of the communication destination (S21).

[0077] The communication unit 13 of the terminal 10 acquires information on the APN corresponding to the bearer shared with the EPC device 50 (S22). In addition, the processing unit 11 reduces the metric value in the communication control information of the default route for communication via the 3GPP network N2 held in the routing table in order to increase the priority of the 3GPP network N2 as a network to be used for communication (S22). The communication unit 13 refers to the routing table, transmits information on the APN to the DNS server 70, and inquires about network identification information of the communication destination (S23).

[0078] The communication unit 73 of the DNS server 70 acquires the APN information from the terminal 10. The processing unit 71 refers to the database, extracts the network identification information of the communication destination corresponding to the APN, and notifies the terminal 10 via the communication unit 73 (S24). This network identification information corresponds to, for example, information that the terminal 10 transmits to the 3GPP network N2.

[0079] The communication unit 13 of the terminal 10 receives destination network identification information from the DNS server 70 (S25). The processing unit 11 registers communication control information CC1 including the destination network identification information in the routing table (S25). Then, the processing unit 11 increases the metric value in the communication control information of the default route for communication via the 3GPP network N2 held in the routing table in order to lower the priority of the 3GPP network N2 as a network to be used for communication (S25).

[0080] In this way, by the communication system 5A1 performing the first operation example, the terminal 10 can select communication toward the gateway 30 by increasing the priority for selecting the 3GPP network N2 held as a default route in the routing table, and can reliably select the 3GPP network N2. Therefore, even if the priority of the default route related to the 3GPP network N2 is initially set lower than the priority of the default route related to the non-3GPP network N1, the terminal 10 can reach the DNS server 70 arranged in the 3GPP network N2. Therefore, the DNS server 70 can be accessed, and network identification information of the communication destination corresponding to the APN can be obtained. Therefore, the terminal 10 can register individual communication control information CC1 of the communication destination, and can communicate according to the communication control information CC1.

[0081] Moreover, by lowering the priority for selecting the 3GPP network N2 after acquiring the network identification information of the communication destination, the terminal 10 can restore the state of the routing table before starting the process in Fig. 7. Therefore, after acquiring the network identification information of the communication destination, the terminal 10 can prevent only communication via the 3GPP network N2 from being selected and communication via the non-3GPP network N1 from being disabled.

[0082] Therefore, the terminal 10 can perform communication via another communication route only for the specific communication (here, communication from the terminal 10 to the DNS server 70) while maintaining communication via the default communication route according to the communication control information held in the routing table. This allows communication between the terminal 10 and the DNS server 70 to be realized even if the DNS server 70 can be reached only via one of the multiple networks. Also, if the DNS server 70 can be reached via any of the multiple networks, it is possible to prioritize the preferred network by designating the more preferred network as the specific communication.

[0083] 8 is a sequence diagram showing a second operation example of the communication system 5A1, in which the IP address of the DNS server 70 is taken into consideration.

[0084] It is assumed that individual communication control information of the communication destination is not held in the routing table at the start of the process of Fig. 8. It is also assumed that, as an example, the non-3GPP network N1 is set to be selected preferentially over the 3GPP network N2 according to communication control information of a default route held in the routing table at the start of the process of Fig. 8. It is also assumed that individual communication control information for communicating with the DNS server 70 is not registered in the routing table at the start of the process of Fig. 8.

[0085] First, the PGW 51 of the EPC device 50 performs the process of S21. The communication unit 13 of the terminal 10 acquires information of the APN corresponding to the bearer shared with the EPC device 50 (S22B). In addition, the communication unit 13 acquires network identification information for identifying the network to which the DNS server 70 belongs, for example, when the bearer is established (S22B). The network identification information of the DNS server 70 may include IP address and netmask information, similar to the network identification information of the communication destination. The processing unit 11 of the terminal 10 may acquire the network identification information of the DNS server 70 from the DNS server 70 itself via the communication unit 13, may acquire it from another communication device via the communication unit 13, or may hold it in the storage unit 12 and acquire it from the storage unit 12. The processing unit 11 registers individual communication control information including the individual network identification information of the DNS server 70 in the routing table (S22B). As a result, the processing unit 11 specifies a route to the DNS server 70 (S22B). Information other than the network identification information in the individual communication control information of the DNS server 70 may be set, for example, via the operation unit 14, or may be set by obtaining information held by the terminal 10, in the same manner as the communication control information of the communication destination.

[0086] The terminal 10 performs the processes of S23 and S24. The communication unit 13 receives the network identification information of the communication destination from the DNS server 70, and registers the communication control information CC1 including the network identification information of the communication destination in the routing table (S25B). The processing unit 11 also deletes the communication control information of the DNS server 70 from the routing table (S25B). Note that the deletion of the communication control information of the DNS server 70 from the routing table may be omitted.

[0087] In this way, by the communication system 5A1 performing the second operation example, the terminal 10 can directly register the communication control information of the DNS server 70 in the routing table and communicate according to this communication control information. Therefore, even if the priority of the default route related to the 3GPP network N2 is set lower than the priority of the default route related to the non-3GPP network N1 in the routing table, the terminal 10 can directly specify the route to the DNS server 70 by the individual communication control information of the DNS server 70, and can reach the DNS server 70 arranged in the 3GPP network N2. Therefore, the DNS server 70 can be accessed, and network identification information of the communication destination corresponding to the APN can be obtained. Therefore, the terminal 10 can register the individual communication control information CC1 of the communication destination, and can communicate according to the communication control information CC1.

[0088] (Second example of DNS server placement) Next, a second specific example of the arrangement of the DNS server 70 will be shown. Fig. 9 is a block diagram showing the second example of the arrangement of the DNS server 70 in the communication system 5. In the communication system 5A2, which is the communication system 5 incorporating the second example of the arrangement of the DNS server 70, the same components as those in the communication system 5 shown in Fig. 1 or 6 are denoted by the same reference numerals, and the description thereof will be omitted or simplified.

[0089] In the communication system 5A2, the DNS server 70 is disposed inside the EPC device 50. Therefore, the terminal 10 does not have direct communication with the DNS server 70. In other words, since the DNS server 70 exists inside the EPC device 50, the terminal 10 does not substantially recognize the DNS server 70 in the EPC device 50.

[0090] The DNS server 70 may have its functions integrated into a device (server) together with other functions within the EPC device 50, or may be configured as a physically separate device (server). In either case, the following description will be given assuming that the functions related to processing, storage, and communication by the DNS server 70 are performed by a processing unit 71, a storage unit 72, and a communication unit 73, respectively.

[0091] FIG. 10 is a sequence diagram showing a first operation example of the communication system 5A2. In FIG. 10, it is assumed that the gateway 30 operates as a DNS cache server. That is, the gateway 30 may have a DNS cache server 70c as a DNS server smaller in size than the DNS server 70 in the EPC device 50. The storage unit 32 of the gateway 30 has a database DB2 that associates and holds the APN and the network identification information, similar to the DNS server 70. However, the database DB2 of the gateway 30 is smaller in size than the database DB of the DNS server 70 arranged inside the EPC device 50. Therefore, although the database DB of the DNS server 70 holds the APN and its network identification information, it may not be held in the database DB2 of the DNS cache server 70c of the gateway 30.

[0092] It is assumed that individual communication control information of the communication destination is not held in the routing table at the start of the process of Fig. 10. It is also assumed that, as an example, at the start of the process of Fig. 10, the non-3GPP network N1 is set to be selected with priority over the 3GPP network N2 according to communication control information of a default route held in the routing table.

[0093] First, the PGW 51 of the EPC device 50 establishes a bearer with the terminal 10 via the gateway 30 (S31). The PGW 51 assigns an IP address to the terminal 10 corresponding to the bearer, and determines an APN corresponding to the connection destination of the external network to which the bearer is connected (S31). The APN information is shared between the EPC device 50 and the terminal 10, and is held in each memory unit.

[0094] The communication unit 13 of the terminal 10 acquires information on the APN corresponding to the bearer shared with the EPC device 50 (S32). The processing unit 11 transmits the information on the APN to the gateway 30 via the communication unit 13, and inquires about network identification information of the communication destination (S33A1).

[0095] The communication unit 33 of the gateway 30 receives the information of the APN. The processing unit 31 refers to the database DB2 and searches for the network identification information of the communication destination corresponding to the APN. If the network identification information of the communication destination corresponding to the APN exists in the database DB2 of the DNS cache server 70c, the processing unit 31 does not inquire the DNS server 70 inside the EPC device 50 via the communication unit 33. In this case, the network identification information of the communication destination can be resolved within the gateway 30. On the other hand, if the network identification information of the communication destination does not exist in the database DB2 of the DNS cache server 70c, the processing unit 31 transmits the information of the APN to the EPC device 50 having the DNS server 70 via the communication unit 33 and inquires about the network identification information of the communication destination (S33A2).

[0096] The communication unit 73 of the DNS server 70 in the EPC device 50 receives the APN information. The processing unit 71 refers to the database DB, and searches for and extracts the network identification information of the communication destination corresponding to the APN. The communication unit 73 transmits the extracted network identification information of the communication destination to the gateway 30 (S34A1). The communication unit 33 of the gateway 30 receives the network identification information of the communication destination from the EPC device 50, and transmits it to the terminal 10 (S34A2). This network identification information corresponds to, for example, information for the terminal 10 to transmit to the 3GPP network N2.

[0097] The communication unit 13 of the terminal 10 receives the network identification information of the communication destination from the gateway 30. The processing unit 11 registers the communication control information CC1 including the network identification information of the communication destination in the routing table (S35).

[0098] In this way, by implementing the first operation example, the communication system 5A2 does not need to access the DNS server 70 installed independently of the EPC device 50, and therefore the terminal 10 does not need to add or change information in the routing table. In other words, it is sufficient for the gateway 30 to be aware of communication with the EPC device 50. Even in this case, the DNS server 70 can perform necessary processing within the EPC device 50. Also, the terminal 10 can autonomously inquire about network identification information of the communication destination corresponding to the APN, and the gateway 30 can provide the network identification information of the communication destination while suppressing the processing load.

[0099] Fig. 11 is a sequence diagram showing a second operation example of the communication system 5A2. In Fig. 11, it is assumed that the gateway 30 takes the initiative in inquiring about address information of the communication destination of the terminal 10.

[0100] It is assumed that individual communication control information of the communication destination is not held in the routing table at the start of the process of Fig. 11. It is also assumed that, as an example, at the start of the process of Fig. 11, the non-3GPP network N1 is set to be selected with priority over the 3GPP network N2 according to communication control information of a default route held in the routing table.

[0101] First, the PGW 51 of the EPC device 50 executes S31. The communication unit 33 of the gateway 30 acquires information on the APN corresponding to the bearer shared with the EPC device 50 (S32B). In this case, the communication unit 33 may receive and acquire the APN information from the terminal 10, for example. The processing unit 31 transmits the APN information to the EPC device 50 having the DNS server 70 via the communication unit 33, and inquires about network identification information of the communication destination (S33B).

[0102] The communication unit 73 of the DNS server 70 in the EPC device 50 receives the APN information. The processing unit 71 refers to the database DB, and searches for and extracts the network identification information of the communication destination corresponding to the APN. The communication unit 73 transmits the network identification information of the communication destination to the gateway 30 (S34B1). The communication unit 33 of the gateway 30 receives the network identification information of the communication destination from the EPC device 50, and transmits it to the terminal 10 (S34B2). This network identification information corresponds to, for example, information that the terminal 10 transmits to the 3GPP network N2. Then, the terminal 10 performs the process of S35.

[0103] In this way, by implementing the second operation example, the communication system 5A2 does not need to access the DNS server 70 installed independently of the EPC device 50, and therefore the terminal 10 does not need to add or change information in the routing table. In other words, it is sufficient for the gateway 30 to be aware of communication with the EPC device 50. Even in this case, the DNS server 70 can perform necessary processing within the EPC device 50. Furthermore, the terminal 10 can acquire route information of the communication connection destination corresponding to the APN by having the gateway 30 take the initiative in making an inquiry, without the terminal 10 taking the initiative in inquiring about network identification information of the communication destination.

[0104] In addition, in the second operation example shown in Fig. 11, the gateway 30 may have the DNS cache server 70c. In this case, if the network identification information corresponding to the APN can be resolved by the gateway 30 alone, the process related to providing the network control information of the communication destination may be completed in the gateway 30 without making an inquiry to the EPC device 50.

[0105] Generally, in a communication system capable of both communication in a non-3GPP network N1 and communication in a 3GPP network N2, which of the 3GPP network and the non-3GPP network is to be preferentially selected depends on the implementation, but the 3GPP network may be selected. This is to obtain the benefits of communication using the 3GPP network. In this case, communication via the non-3GPP network may not be possible. Conversely, the implementation may be such that communication via the non-3GPP network is possible and communication via the 3GPP network is not possible. Also, the non-3GPP network may be selected. This is because a communication method with a narrower communication range is often preferred. In this case, communication via the 3GPP network may not be possible. Conversely, the implementation may be such that communication via the 3GPP network is possible and communication via the non-3GPP network is not possible.

[0106] In contrast, the communication system 5 can flexibly select a network and improve communication performance. Therefore, the communication system 5 can prevent one of the multiple networks in the non-3GPP network N1 and the 3GPP network N2 from being uniformly selected according to the default route of the routing table. In addition, the communication system 5 can use existing LTE technologies such as APN and DNS.

[0107] Specifically, in the communication system 5, the DNS server 70 holds in a database various APNs and network identification information for identifying a communication destination network corresponding to the APN. This allows the DNS server 70 to provide the network identification information in response to a query from an external party (e.g., the terminal 10).

[0108] Furthermore, the terminal 10 acquires network identification information of the communication destination of the terminal 10, and registers the individual communication control information CC1 of the communication destination including the network identification information in the routing table. Thus, unlike the case where the terminal 10 uses communication control information of a default route stored in the routing table, the terminal 10 is able to communicate via a user-desired network described in the individual communication control information CC1 of the communication destination. Thus, the terminal 10 can, for example, select a network with a low communication load or a network through which communication data can reach the communication destination of the terminal 10, and can improve (for example, optimize) the suitability of the communication route for communicating with the communication destination.

[0109] Also, for example, according to the communication system 5, when the communication system has a terminal 10B and a gateway 30B, if the terminal 10B is capable of using both the LTE network and the wireless LAN network, like a smartphone, the terminal 10B can select the LTE network intended by the user without automatically prioritizing the router 60, and can perform individual communication via LTE.

[0110] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can come up with various modified or amended examples within the scope of the claims, and it is understood that these also naturally belong to the technical scope of the present invention. In addition, the components in the various embodiments described above may be arbitrarily combined within the scope of the invention.

[0111] In the above embodiment, there may be a plurality of terminals 10 and a plurality of communication destinations of the terminals 10. In this case, the APN corresponding to each communication destination may be different, and different network identification information may be provided for the different APNs. In this case, the communication control information including the network identification information of each communication destination of each terminal 10 may include information using communication via different networks. That is, a certain terminal 10 may be set to communicate via a non-3GPP network N1, and a certain terminal 10 may be set to communicate via a 3GPP network N2. This allows the communication system 5 to distribute the load related to communication between each terminal 10 and its communication destination, thereby improving communication efficiency.

[0112] In the above embodiment, the DNS server 70 is provided, but other servers may be provided. The other servers may be, for example, servers that respond with destination network identification information in response to a query for destination identification information (e.g., APN). In addition, other identification information may be used as the destination identification information instead of the APN.

[0113] In the above embodiment, the multiple networks are mainly exemplified as a non-3GPP network N1 and a 3GPP network N2, but are not limited thereto. For example, the multiple networks may be multiple networks in the non-3GPP network N1, may be multiple networks in the 3GPP network N2, or may be a combination of these networks. For example, the multiple networks may be multiple LTE networks. This makes the above embodiment very useful for a terminal that cannot roam in a foreign country.

[0114] As described above, in the communication system 5 of the above embodiment, the DNS server 70 (an example of a server) may be disposed in the 3GPP network N2 or the non-3GPP network N1. The DNS server 70 may acquire communication destination identification information that identifies a communication destination of the terminal 10 that can communicate in both the 3GPP network N2 and the non-3GPP network N1. The DNS server 70 may transmit, to the terminal 10, network identification information that identifies a network to which the communication destination belongs, based on the communication destination identification information.

[0115] This allows the DNS server 70 to provide network identification information in response to an inquiry from outside (for example, the terminal 10). Therefore, the DNS server 70 can support, for example, the terminal 10 to register communication control information including network identification information and communicate according to individual communication control information different from a default route. Thus, the DNS server 70 can support the terminal 10 to select, for example, a network with a low communication load or a network through which communication data can reach the communication destination of the terminal 10, thereby improving the suitability of a communication path for communicating with a communication destination.

[0116] Furthermore, in the communication system 5, the terminal 10 may acquire network identification information from the DNS server 70. The terminal 10 may store communication control information CC1, which includes the network identification information and is used to communicate with a communication destination, in a routing table (an example of a table).

[0117] This allows the terminal 10 to communicate via a user-desired network described in the individual communication control information CC1, unlike when using communication control information of a default route stored in a routing table. Therefore, the terminal 10 can select, for example, a network with a low communication load or a network through which communication data can reach the communication destination of the terminal 10, thereby improving the suitability of the communication path for communicating with the communication destination.

[0118] Furthermore, the terminal 10 may obtain, as the communication destination identification information, information on the APN corresponding to the communication destination, transmit the APN information to the DNS server 70, and obtain network identification information corresponding to the APN from the DNS server 70.

[0119] The APN is an identifier of a network higher than the EPC device 50, and coincides with identification information of a communication destination disposed in an external network higher than the EPC device 50. Therefore, the APN is closely related to information of a network to be accessed via the EPC device 50, and is a concept that goes well with the information. Therefore, the terminal 10 can easily obtain network identification information by using the APN.

[0120] Furthermore, the DNS server 70 may be placed in a network higher than the EPC device 50 (an example of a core network device) that manages communication in the 3GPP network N2. The terminal 10 may transmit APN information to the DNS server 70 after raising the priority for selecting communication via the 3GPP network N2. The terminal 10 may lower the priority after acquiring network identification information of the communication destination from the DNS server 70.

[0121] As a result, even if the individual communication control information of the DNS server 70 is not registered in the routing table and the terminal 10 communicates along a default route, by increasing the priority of communication via the 3GPP network N2, the terminal 10 can reach the DNS server 70 arranged on the 3GPP network N2 side and communicate with the DNS server 70. In addition, by lowering the priority of communication via the 3GPP network N2 after the terminal 10 acquires the network identification information of the communication destination from the DNS server 70, it is possible to prevent the selection of the network according to the default route in subsequent communication from being changed and maintained due to a change in priority.

[0122] The DNS server 70 may be disposed in a network higher than the EPC device 50 that manages communication in the 3GPP network N2. The terminal 10 may store second communication control information for communicating with the DNS server 70 in a routing table, and transmit APN information to the server based on the second communication control information.

[0123] As a result, by registering the individual communication control information of the DNS server 70 in the routing table, the terminal 10 can communicate according to the individual communication control information, reach the DNS server 70 located on the 3GPP network N2 side, and communicate with the DNS server 70.

[0124] Furthermore, the gateway 30 (an example of a relay device or gateway device) of the communication system 5 may relay communication between the terminal 10 and the EPC device 50. The DNS cache server 70c (an example of a server) may be disposed inside the gateway 30. The terminal 10 may transmit information of an APN to the gateway 30 and obtain network identification information corresponding to the APN from the gateway 30.

[0125] This allows the terminal 10 to take the initiative in making an inquiry to the relay device about the network identification information of the communication destination at the necessary timing. Also, the communication system 5 can use the function of the gateway 30 as an auxiliary DNS cache server 70c. For example, the gateway 30 has a database smaller than that of the DNS server 70, and when the database of the gateway 30 is sufficient, it can notify the terminal 10 of the network identification information of the communication destination without making an inquiry to the EPC device 50.

[0126] In addition, the DNS cache server 70c may be disposed inside the gateway 30, and the DNS server 70 may be disposed inside the EPC device 50. The gateway 30 may obtain APN information from the terminal 10 and transmit it to the EPC device 50. The gateway 30 may obtain network identification information corresponding to the APN from the EPC device 50 and transmit it to the terminal 10.

[0127] This allows the gateway 30 to take the initiative in inquiring about network information of the communication destination of the terminal 10 and provide it to the terminal 10. Even when the terminal 10 takes the initiative in inquiring about network identification information of the communication destination, if the auxiliary DNS cache server 70c held by the gateway 30 is insufficient for searching for network identification information, the gateway 30 can further inquire about the network identification information of the EPC device 50, obtain it from the EPC device 50, and notify the terminal 10.

[0128] The network identification information may include information on an address range that includes the IP address of the communication destination. The communication control information may include the network identification information and information on an interface for communicating with the communication destination.

[0129] As a result, the terminal 10 registers the communication control information in the routing table, and thus can grasp information about the destination network. Also, the terminal 10 can communicate with the destination network identified by the registered network identification information by using the registered interface by referring to the routing table.

[0130] Furthermore, the terminal 10 may be a terminal 10A that is a non-3GPP terminal, and the gateway 30 may be a gateway 30A that accommodates the terminal 10A in the 3GPP network N2.

[0131] When the terminal 10A is accommodated in the 3GPP network N2, for example, the network is often set to be selected as the 3GPP network N2. In this case, it becomes difficult for the terminal 10A to select the non-3GPP network N1 as the network to be used for communication. Even in this case, communication using a network desired by the user is possible based on the individual communication control information CC1 of the communication destination, and it is possible to prevent only a specific network from being selected. Therefore, the communication system 5 can suppress the occurrence of communication failure events and excessive communication loads.

[0132] Furthermore, the terminal 10 may be a terminal 10B that is a 3GPP terminal, and the gateway 30 may be a base station device (eNB) in the 3GPP network N2.

[0133] This allows the terminal 10B to communicate using a network desired by the user based on the individual communication control information CC1 of the communication destination. Therefore, the terminal 10B can prevent the non-3GPP network from being automatically selected preferentially, even though both the 3GPP network N2 and the non-3GPP network N1 are available, as in the case of a smartphone, for example. Therefore, the communication system 5B can prevent communication failure events and excessive communication loads from occurring. [Industrial Applicability]

[0134] INDUSTRIAL APPLICABILITY The present invention is useful for a communication system, a terminal, a communication control method, etc., which can prevent a terminal connectable to multiple networks including a 3GPP network or a non-3GPP network from becoming unable to communicate or from experiencing an excessive communication load. [Explanation of symbols]

[0135] 5. Communication Systems 10, 10A, 10B Terminal 30,30A,30B Gateway 31 Processing section 32 Storage section 33 Communications Department 50 EPC equipment 51 PGW 53 S.G.W. 54 MME 55 HSS 60 Router 70 DNS Server 70c DNS cache server DB, DB2 database N1 Non-3GPP network N2 3GPP network TB Routing Table

Claims

1. A communication system comprising a server, The server, Deployed in a Third Generation Partnership Project (3GPP) network or a non-3GPP network; Obtaining communication destination identification information that identifies a communication destination of a terminal capable of communicating in both the 3GPP network and the non-3GPP network; transmitting, to the terminal, network identification information including information on an IP address and a netmask for identifying a network to which the communication destination belongs, based on the communication destination identification information; Communication systems.

2. The terminal further comprises: The terminal includes: Obtaining the network identification information from the server; storing communication control information for communicating with the communication destination, the communication control information including the network identification information, in a table; The communication system according to claim 1 .

3. The terminal includes: Acquire information on an Access Point Name (APN) corresponding to the communication destination as the communication destination identification information, Sending the APN information to the server; obtaining the network identification information corresponding to the APN from the server; The communication system according to claim 2 .

4. The server is disposed in a network higher than an EPC (Evolved Packet Core) device that manages communications in the 3GPP network, The terminal includes: After increasing the priority for selecting communication via the 3GPP network, transmit information of the APN to the server; lowering the priority after obtaining the network identification information from the server; The communication system according to claim 3.

5. The server is disposed in a network higher than an EPC device that manages communications in the 3GPP network, The terminal includes: storing second communication control information for communicating with the server in the table; transmitting information of the APN to the server based on the second communication control information; The communication system according to claim 3.

6. A relay device that relays communication between the terminal and an EPC device that manages communication in the 3GPP network, the server is disposed inside the relay device, The terminal includes: Transmitting information of the APN to the relay device; obtaining the network identification information corresponding to the APN from the relay device; The communication system according to claim 3.

7. The present invention further comprises a relay device that relays communication between the terminal and an EPC device that manages communication in the 3GPP network, The server is disposed within the EPC device; The relay device is Acquire information of an APN corresponding to the communication destination as the communication destination identification information and transmit the information to the EPC device; Obtaining the network identification information corresponding to the APN from the EPC device and transmitting the network identification information to the terminal; The communication system according to claim 2 .

8. The server is a Domain Name System (DNS) server. A communication system according to any one of claims 1 to 7.

9. The network identification information includes information on an address range that includes the IP address of the communication destination. A communication system according to any one of claims 1 to 8.

10. The communication control information includes the network identification information and information of an interface for communicating with the communication destination. A communication system according to any one of claims 2 to 7.

11. A relay device that relays communication between the terminal and an EPC device that manages communication in the 3GPP network, the terminal is a non-3GPP terminal, the non-3GPP terminal is capable of communicating via the non-3GPP network, and further has a function of communicating via the 3GPP network with the assistance of communication control by the relay device; The relay device is a gateway device that accommodates the non-3GPP terminal in the 3GPP network. A communication system according to any one of claims 1 to 10.

12. A relay device that relays communication between the terminal and an EPC device that manages communication in the 3GPP network, The terminal is a 3GPP terminal, The 3GPP terminal is capable of communicating via the 3GPP network and further has a function of communicating via the non-3GPP network; The relay device is a base station device in the 3GPP network. A communication system according to any one of claims 1 to 10.

13. A terminal capable of communicating in both a 3GPP network and a non-3GPP network, A communication unit and a processing unit are provided, The communication unit receives the network identification information from a server that is disposed in the 3GPP network or the non-3GPP network and transmits network identification information including information on an IP address and a netmask that identify a network of the communication destination based on communication destination identification information that identifies the communication destination of the terminal; the processing unit causes communication control information for communicating with the communication destination, the communication control information including the network identification information, to be stored in a table. Terminal.

14. A communication control method in a server disposed in a 3GPP network or a non-3GPP network, comprising: Obtaining communication destination identification information that identifies a communication destination of a terminal capable of communicating in both the 3GPP network and the non-3GPP network; transmitting, to the terminal, network identification information including information on an IP address and a netmask for identifying the network of the communication destination based on the communication destination identification information; Communications control method.

15. A communication control method in a terminal capable of communicating in both a 3GPP network and a non-3GPP network, comprising: receiving network identification information from a server disposed in the 3GPP network or the non-3GPP network, the server transmitting network identification information including information on an IP address and a netmask for identifying a network of a communication destination based on communication destination identification information for identifying a communication destination of the terminal; storing communication control information for communicating with the communication destination, the communication control information including the network identification information, in a table; Communications control method.

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