Base station device and communication system

Abstract

To provide a base station device and a communication system that can suppress the impact of attacks on a network.SOLUTION: A base station device includes: a receiving unit that receives a first message transmitted from a terminal device; a processing unit that, when the first message is received, determines whether information corresponding to the received first message is information indicating an initial connection procedure between the terminal device and a network or not; and a transmitting unit that, when it is determined that the information corresponding to the first message is information indicating an initial connection procedure, transmits the first message to a first communication control device, and, when it is determined that the information corresponding to the first message is not information indicating an initial connection procedure, transmits the first message to a second communication control device.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a base station device and a communication system. [Background technology]

[0002] In recent years, the threat of cyber attacks against various critical infrastructures has become apparent, and it is expected that the threat of cyber attacks will also become apparent in mobile networks (hereinafter simply referred to as networks) that comply with the communication standards of the 5th generation mobile communications (hereinafter simply referred to as 5G). Specifically, such networks may be subject to Denial of Service attacks, which place excessive load on the network using, for example, fraudulently manufactured terminal devices (hereinafter simply referred to as fraudulent terminal devices).

[0003] Therefore, in such a network, for example, a process for authenticating the terminal device (hereinafter also referred to as authentication process) is performed in the connection procedure with the terminal device, thereby prohibiting unauthorized terminal devices from accessing the network (see, for example, Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2019-534653 [Patent Document 2] Patent Publication No. 2022-020748 [Patent Document 3] International Publication No. 2021 / 030077 [Patent Document 4] US Patent Application Publication No. 2020 / 0267554 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned network, even if an authentication process is performed in the connection procedure with a terminal device, it may not be possible to prevent attacks against each device that performs each process up to the authentication process.

[0006] Therefore, in one aspect, the present invention has an object to provide a base station device and a communication system that can reduce the impact of attacks on a network. [Means for solving the problem]

[0007] In one aspect of the embodiment, a base station device is a base station device capable of communicating with both a first communication control device in a network and a second communication control device in the network, and has a receiving unit that receives a first message transmitted from a terminal device, a processing unit that, when the first message is received, determines whether information corresponding to the received first message is information indicating an initial connection procedure between the terminal device and the network, and a transmitting unit that, when it is determined that the information corresponding to the first message is information indicating the initial connection procedure, transmits the first message to the first communication control device, and, when it is determined that the information corresponding to the first message is not information indicating the initial connection procedure, transmits the first message to the second communication control device. Effect of the Invention

[0008] According to one aspect, it is possible to reduce the impact of attacks on a network. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a communication system 100. As shown in FIG. [Diagram 2] FIG. 2 is a diagram illustrating the configuration of the communication system 100. As shown in FIG. [Diagram 3] FIG. 3 is a diagram for explaining the hardware configuration of the CU1. [Figure 4]FIG. 4 is a diagram for explaining the hardware configuration of the AMF 2. [Diagram 5] FIG. 5 is a diagram for explaining the hardware configuration of the AMF 3. [Figure 6] FIG. 6 is a diagram illustrating the function of the CU1 in the first embodiment. [Figure 7] FIG. 7 is a diagram illustrating the function of the AMF 2 in the first embodiment. [Figure 8] FIG. 8 is a diagram illustrating the function of the AMF 3 in the first embodiment. [Figure 9] FIG. 9 is a flowchart of the communication control process in the first embodiment. [Figure 10] FIG. 10 is a flowchart of the communication control process in the first embodiment. [Figure 11] FIG. 11 is a flowchart of the communication control process in the first embodiment. [Figure 12] FIG. 12 is a sequence chart illustrating the communication control process in the first embodiment. [Figure 13] FIG. 13 is a sequence chart illustrating the communication control process in the first embodiment. [Figure 14] FIG. 14 is a flowchart of the communication control process in the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. However, such descriptions should not be interpreted in a limiting sense and do not limit the subject matter described in the claims. In addition, various changes, substitutions, and modifications can be made without departing from the spirit and scope of the present disclosure. In addition, different embodiments can be appropriately combined.

[0011] [Configuration of the communication system in the first embodiment] First, a configuration of the communication system 100 will be described. Figures 1 and 2 are diagrams for explaining the configuration of the communication system 100. Below, a case will be described in which the communication system 100 is a communication system compatible with the 5G communication standard.

[0012] As shown in FIG. 1, the communication system 100 includes, for example, a UE (User Equipment) 6, a Radio Access Network (RAN) 10 that establishes a wireless connection with the UE 6, and a Core Network 20 that establishes a wired connection with the RAN 10.

[0013] Specifically, the RAN 10 includes, for example, a CU (Central Unit) 1, a DU (Dustribeted Unit) 4, and a RU (Radio Unit) 5. Furthermore, the core network 20 includes, for example, an AMF (Access and Mobility Management Function) 2. Hereinafter, the CU 1 is also referred to as a base station device 1, and the UE 6 is also referred to as a terminal device 6. Hereinafter, the AMF 2 is also referred to as a second communication control device 2 or a normal processing AMF 2.

[0014] The CU1 is, for example, a physical machine or a virtual machine, and is a device that controls the DU 4 and the RU 5 and communicates with the core network 20. Specifically, the CU1 communicates with, for example, the AMF 2, as shown in FIG.

[0015] The DU 4 is, for example, a physical machine or a virtual machine, and is a device that modulates and demodulates signals transmitted and received between the DU 4 and the RU 5, and intermediates communication between the CU 1 and the RU 5.

[0016] The RU 5 is, for example, a physical machine or a virtual machine, and is a device that communicates with the UE 6 via an antenna (not shown). Specifically, the RU 5 converts, for example, radio waves transmitted from the UE 6 into signals and transmits the signals to the DU 4. The RU 5 also converts, for example, signals transmitted from the DU 4 into radio waves and transmits the signals to the UE 6.

[0017] More specifically, in the example shown in Fig. 1, the UE 6a communicates with the core network 20 via, for example, the RU 5a, the DU 4a, and the CU 1, and the UE 6b communicates with the core network 20 via, for example, the RU 5b, the DU 4a, and the CU 1. Also, in the example shown in Fig. 1, the UE 6c communicates with the core network 20 via, for example, the RU 5c, the DU 4b, and the CU 1, and the UE 6d communicates with the core network 20 via, for example, the RU 5d, the DU 4b, and the CU 1.

[0018] Note that, hereinafter, a case where the communication system 100 has four UEs 6 will be described, but the communication system 100 may have, for example, a number of UEs 6 other than four. Also, hereinafter, a case where the communication system 100 has one CU1 will be described, but the communication system 100 may have, for example, a number of CUs 1 other than one. Also, hereinafter, a case where the communication system 100 has two DUs 4 will be described, but the communication system 100 may have, for example, a number of DUs 4 other than two. Also, hereinafter, a case where the communication system 100 has four RUs 5 will be described, but the communication system 100 may have, for example, a number of RUs 5 other than four.

[0019] The AMF2 is, for example, a physical machine or a virtual machine, and is a device that performs authentication processing, security processing, and location management processing of messages transmitted from the UE 6 via the RU 5, DU 4, and CU 1 in cooperation with other devices (not shown) constituting the core network 20. Specifically, the AMF2 prohibits unauthorized terminal devices from accessing the core network 20 by performing authentication processing of the UE 6 in a connection procedure with the UE 6. The AMF2 performs authentication processing, security processing, and location management processing (hereinafter also simply referred to as authentication processing, etc.) in cooperation with, for example, an AUSF (Authentication Server Function) not shown, an SMF (Session Management Function) not shown, and a UDM (Unified Data Management) not shown.

[0020] Here, in the above-described communication system 100, even if an authentication process is performed in the connection procedure with UE 6, it may not be possible to prevent attacks against each device (e.g., AMF 2) that performs each process up to the authentication process.

[0021] Therefore, as shown in FIG. 2, the core network 20 in this embodiment further includes, in addition to the AMF 2, an AMF 3 (hereinafter, also referred to as first communication control device 3 or initial connection AMF 3).

[0022] Then, the CU1 in this embodiment receives, for example, a message (hereinafter also referred to as a first message) transmitted from the UE 6. The first message is, for example, a Registration Request (hereinafter also simply referred to as a Registration Request) in the NAS (Non-Access-Stratum protocol). In addition, the first message is, for example, an RRC (Radio Resource Control) Setup Request.

[0023] Next, when CU1 receives a first message, for example, CU1 determines whether or not information corresponding to the received first message is information indicating an initial connection procedure between UE 6 and the core network 20 (hereinafter also simply referred to as an initial connection procedure). The information corresponding to the first message is, for example, information included in the first message. The initial connection procedure is, for example, a connection procedure performed when UE 6 first connects to the communication system 10. Specifically, in this case, CU1 determines whether the information corresponding to the received first message is information indicating either an initial connection procedure or a reconnection procedure. The reconnection procedure is, for example, a connection procedure performed when UE 6 reconnects to the communication system 10.

[0024] As a result, for example, when it is determined that the information corresponding to the received first message is information indicating an initial connection procedure, the CU1 transmits the received first message to the AMF 3. On the other hand, when it is determined that the information corresponding to the first message is not information indicating an initial connection procedure, the CU1 transmits the received first message to the AMF 2.

[0025] That is, when a DoS attack is carried out against the communication system 10, it can be determined that the UE 6 (unauthorized terminal device) used in the DoS attack is highly likely to perform an initial connection procedure with the core network 20. For this reason, when the CU1 in this embodiment determines that the information corresponding to the first message transmitted from the UE 6 is not information indicating an initial connection procedure, it causes the AMF 2 to perform authentication processing, etc. On the other hand, when the CU1 determines that the information corresponding to the first message transmitted from the UE 6 is information indicating an initial connection procedure, it causes the AMF 3 different from the AMF 2 to perform authentication processing, etc.

[0026] As a result, even if, for example, a DoS attack is carried out and a large amount of first messages are transmitted from an unauthorized terminal device, the communication system 10 in this embodiment can suppress the effect of this attack on the AMF 2. Therefore, even if, for example, a DoS attack is carried out, the communication system 10 can limit the scope of the effect of this attack.

[0027] [Hardware configuration of communication system] Next, the hardware configuration of the communication system 100 will be described. Fig. 3 is a diagram for explaining the hardware configuration of the CU1. Fig. 4 is a diagram for explaining the hardware configuration of the AMF2. Fig. 5 is a diagram for explaining the hardware configuration of the AMF3.

[0028] First, a description will be given of the hardware configuration of the CU 1. As shown in Fig. 3, the CU 1 has, for example, a CPU (Central Processing Unit) 101, which is a processor, a memory 102, a communication device (I / O interface) 103, and a storage device 104. Each part is connected to each other via a bus 105.

[0029] The storage device 104 has, for example, a program storage area (not shown) that stores a program 110 for performing a process (hereinafter also referred to as a communication control process) for controlling a connection between the UE 6 and the core network 20. The storage device 104 also has, for example, a storage unit 130 (hereinafter also referred to as an information storage area 130) that stores information used when performing the communication control process. The storage device 104 may be, for example, a hard disk drive (HDD) or a solid state drive (SSD).

[0030] The CPU 101 executes, for example, a program 110 loaded from the storage device 104 to the memory 102 to perform communication control processing.

[0031] The communication device 103 communicates with, for example, the DU 4. Also, the communication device 103 communicates with, for example, each of the AMF 2 and the AMF 3.

[0032] Next, a description will be given of the hardware configuration of the AMF 2. As shown in Fig. 4, the AMF 2 has, for example, a CPU 201 which is a processor, a memory 202, a communication device 203, and a storage device 204. Each unit is connected to each other via a bus 205.

[0033] The storage device 204 has, for example, a program storage area (not shown) that stores a program 210 for performing the communication control process. The storage device 204 also has, for example, a storage unit 230 (hereinafter also referred to as information storage area 230) that stores information used when performing the communication control process. The storage device 204 may be, for example, an HDD or an SSD.

[0034] The CPU 201 executes, for example, a program 210 loaded from the storage device 204 to the memory 202 to perform communication control processing.

[0035] The communication device 203 communicates with, for example, the CU1. The communication device 203 also communicates with, for example, the AUSF, SMF, UDM, and the like (hereinafter, these are also collectively referred to as AUSF, and the like).

[0036] Next, a description will be given of the hardware configuration of the AMF 3. As shown in Fig. 5, the AMF 3 has, for example, a CPU 301 which is a processor, a memory 302, a communication device 303, and a storage device 304. Each unit is connected to each other via a bus 305.

[0037] The storage device 304 has, for example, a program storage area (not shown) that stores a program 310 for performing the communication control process. The storage device 304 also has, for example, a storage unit 330 (hereinafter also referred to as an information storage area 330) that stores information used when performing the communication control process. The storage device 304 may be, for example, an HDD or an SSD.

[0038] The CPU 301 executes, for example, a program 310 loaded from the storage device 304 to the memory 302 to perform communication control processing.

[0039] The communication device 303 communicates with, for example, the CU1. The communication device 203 communicates with, for example, the AUSF.

[0040] [Functions of the communication system in the first embodiment] Next, functions of the communication system 100 in the first embodiment will be described. Fig. 6 is a diagram for explaining functions of the CU1 in the first embodiment. Fig. 7 is a diagram for explaining functions of the AMF2 in the first embodiment. Fig. 8 is a diagram for explaining functions of the AMF3 in the first embodiment.

[0041] First, the functions of CU1 will be described. As shown in Fig. 6, for example, hardware such as CPU 101 and memory 102 and a program 110 work together organically to realize various functions including a message receiving unit 111 (hereinafter also simply referred to as receiving unit 111), a procedure determining unit 112 (hereinafter also simply referred to as processing unit 112), an AMF determining unit 113, and a message transmitting unit 114 (hereinafter also simply referred to as transmitting unit 114) as functions for performing communication control processing in CU1.

[0042] The message receiving unit 111 receives, for example, a message transmitted from the UE 6 via the RU 5 and the DU 4. Specifically, the message receiving unit 111 receives, for example, a Registration Request transmitted from the UE 6.

[0043] For example, when message receiving unit 111 receives a message, procedure determining unit 112 determines whether or not information corresponding to the received message (for example, information included in the message) is information indicating an initial connection procedure.

[0044] For example, when procedure determination unit 112 determines that the information corresponding to the message is information indicating an initial connection procedure, AMF determination unit 113 determines that the destination of the message received by message receiving unit 111 is AMF 3. That is, in this case, AMF determination unit 113 determines that, for example, authentication processing of the message received by message receiving unit 111 is to be performed by AMF 3.

[0045] Furthermore, for example, when procedure determination unit 112 determines that the information corresponding to the message is not information indicating an initial connection procedure, AMF determination unit 113 determines that the destination of the message received by message receiving unit 111 is AMF2. That is, in this case, AMF determination unit 113 determines that, for example, authentication processing of the message received by message receiving unit 111 is to be performed by AMF2.

[0046] Message sending unit 114, for example, sends the message received by message receiving unit 111 to the destination determined by AMF determining unit 113. Note that in this case, message sending unit 114 may send another message that has at least a part of information in common with the message received by message receiving unit 111, for example.

[0047] Next, the functions of the AMF 2 will be described. As shown in Fig. 7, the AMF 2 realizes various functions including a message receiving unit 211, a message processing unit 212, and a message sending unit 213 as a function for performing communication control processing in the AMF 2, by organically cooperating with hardware such as a CPU 201 and a memory 202 and a program 210.

[0048] The message receiving unit 211 receives, for example, a message transmitted from the CU 1. Specifically, the message receiving unit 111 receives, for example, a Registration Request transmitted from the CU 1.

[0049] The message processing unit 212 performs, for example, authentication processing of the message received by the message receiving unit 211 .

[0050] The message transmitting unit 213 transmits, for example, a message on which the message processing unit 212 has performed authentication processing or the like, to the AUSF, etc. In this case, the message transmitting unit 213 may transmit, for example, another message having at least a part of information in common with the message received by the message receiving unit 211.

[0051] Next, the functions of the AMF 3 will be described. As shown in Fig. 8, the AMF 3 realizes various functions including a message receiving unit 311, a message processing unit 312, and a message sending unit 313 as a function for performing communication control processing in the AMF 3, by organically cooperating with hardware such as a CPU 301 and a memory 302 and a program 310.

[0052] The message receiving unit 311 receives, for example, a message transmitted from the CU 1. Specifically, the message receiving unit 311 receives, for example, a Registration Request transmitted from the CU 1.

[0053] The message processing unit 312 performs, for example, authentication processing of the message received by the message receiving unit 311 .

[0054] The message transmitting unit 313 transmits, for example, a message on which the message processing unit 312 has performed authentication processing or the like, to the AUSF, etc. In this case, the message transmitting unit 313 may transmit, for example, another message having at least a part of information in common with the message received by the message receiving unit 311.

[0055] The AMF changing unit 314 changes, for example, the AMF that performs a connection procedure with the UE 6 that is the source of the message received by the message receiving unit 311 (hereinafter also simply referred to as the source UE 6) from AMF 3 to AMF 2. That is, the AMF changing unit 314 transmits, for example, information required when performing a connection procedure (reconnection procedure) with the source UE 6 to AMF 2.

[0056] Specifically, in this case, the AMF change unit 314 transmits the context information of the source UE 6 to the AMF 2, in the same manner as when a handover of the UE 6 is performed in accordance with the provisions of 3GPP (registered trademark) (Third Generation Partnership Project).

[0057] [Details of communication control process in the first embodiment] Next, a description will be given of details of the communication control process in the first embodiment. Figures 9 to 11 are flowcharts of the communication control process in the first embodiment.

[0058] First, a flowchart of the communication control process in CU1 will be described.

[0059] As shown in FIG. 9, the message receiving unit 111 waits until it receives a message transmitted from the source UE 6 via the RU 5 and the DU 4 (NO in S1).

[0060] Then, when a message sent from the source UE 6 is received (YES in S1), the procedure determination unit 112 determines, for example, whether or not information corresponding to the received message is information indicating an initial connection procedure between the source UE 6 and the core network 20 (S2).

[0061] As a result, if it is determined that the information corresponding to the message received in the processing of S1 is information indicating an initial connection procedure (YES in S2), the message sending unit 114 sends, for example, the destination of the message received in the processing of S1 to AMF3 (initial connection AMF3) (S3).

[0062] On the other hand, if it is determined that the information corresponding to the message received in the processing of S1 is not information indicating an initial connection procedure (NO in S2), the message sending unit 114, for example, sends the message received in the processing of S1 to AMF2 (normal processing AMF2) (S4).

[0063] Next, a flowchart of the communication control process in AMF2 (normal process AMF2) will be described.

[0064] 10, the message receiving unit 211 waits until it receives a message transmitted from CU1 (NO in S11). That is, the message receiving unit 211 waits until it receives a message that CU1 has determined does not include information indicating an initial connection procedure.

[0065] Then, when a message transmitted from CU1 is received (YES in S11), the message processor 212 performs, for example, authentication processing of the received message (S12).

[0066] Thereafter, when the authentication process or the like of the message is completed in the process of S12 (YES in S13), the message transmitting unit 213 transmits, for example, the message that has been authenticated in the process of S12 to the AUSF or the like (S14).

[0067] On the other hand, if the authentication process of the message is not completed in the process of S12 (NO in S13), the message sending unit 213 does not perform the process of S14, for example. That is, if the authentication of the message fails in the process of S12, for example, the message sending unit 213 does not perform the process of S14. In this case, the message sending unit 213 sends, for example, information indicating that the authentication of the message received in the process of S11 has failed to the source UE 6.

[0068] Next, a flowchart of the communication control process in AMF 3 (initial connection AMF 3) will be described.

[0069] 11, the message receiving unit 311 waits until it receives a message transmitted from CU1 (NO in S21). That is, the message receiving unit 211 waits until it receives a message that CU1 has determined to include information indicating an initial connection procedure.

[0070] Then, when a message transmitted from CU1 is received (YES in S21), the message processor 312 performs, for example, authentication processing of the received message (S22).

[0071] Thereafter, when the authentication process or the like of the message is completed in the process of S22 (YES in S23), the message transmitting unit 313 transmits, for example, the message that has been authenticated in the process of S22 to the AUSF or the like (S24).

[0072] On the other hand, if the authentication process of the message is not completed in the process of S22 (NO in S23), the message transmitting unit 313 does not perform the process of S23, for example. That is, if the authentication of the message fails in the process of S22, for example, the AMF 3 does not perform the process of S23, as in the case of the AMF 2. In this case, the AMF 3 transmits, for example, to the source UE 6, information indicating that the authentication of the message received in the process of S21 has failed.

[0073] As a result, even if, for example, a DoS attack is carried out and a large amount of first messages are transmitted from an unauthorized terminal device, the communication system 10 in this embodiment can suppress the effect of this attack on the AMF 2. Therefore, even if, for example, a DoS attack is carried out, the communication system 10 can limit the range of the effect of this attack.

[0074] Unlike AMF2, AMF3 may receive a large amount of messages transmitted from CU1 due to a DoS attack. Therefore, when AMF3 receives a large amount of messages from CU1, AMF3 may perform authentication processing or the like only on some of the received large amount of messages. In this case, AMF3 may transmit information indicating that authentication of the remaining messages of the received large amount of messages has failed to UE6, which is the source of each message.

[0075] [Specific example of communication control process in the first embodiment] Next, a specific example of the communication control process in the first embodiment will be described. Figures 12 and 13 are sequence charts illustrating the communication control process in the first embodiment.

[0076] First, the UE 6 and the RU 5 perform a random access procedure (RACH: Random Access CHannel procedure) to enable wireless communication between the UE 6 and the RU 5. In the following, a case where a four-step random access procedure is performed between the UE 6 and the RU 5 will be described.

[0077] Specifically, in this case, the UE 6 measures, for example, the RSRP (Reference Signal Received Power) of the SSB (Synchronization Signal Block) broadcast from the RU 5. Then, the UE 6 selects, for example, an SSB whose measured RSRP is equal to or greater than a threshold value previously stored in the UE 6. Thereafter, as shown in FIG. 12, the UE 6 transmits a RACH Preamble to the DU 4 by using, for example, the selected SSB (S101).

[0078] Next, for example, in response to receiving the RACH preamble in the process of S101, the DU 4 transmits a RACH response to the UE 6 (S102).

[0079] After that, the UE 6 transmits, for example, an RRC Setup Request to the CU 1 (S103). Then, the CU 1 transmits, for example, an RRC setup to the UE 6 in response to receiving the RRC Setup Request (S104).

[0080] Next, the UE 6 transmits, for example, a Registration Request in the NAS to the CU 1 (S105). Specifically, the UE 6 transmits, for example, an RRC Setup Complete including the Registration Request to the CU 1.

[0081] Then, for example, in response to receiving a Registration Request in the processing of S105, CU1 determines whether the received Registration Request is a message used for the initial connection procedure between UE 6 and core network 20 (S105, YES in S1 of FIG. 9, S2 in FIG. 9).

[0082] Specifically, in this case, CU1 may refer to the 5GS registration type value in the 5GS registration type information element included in the Registration Request received in the processing of S105, for example.

[0083] If the 5GS registration type value is "000 (initial registration)", the CU1 may determine, for example, that the Registration Request received in the process of S105 is a message used for the initial connection procedure. On the other hand, if the 5GS registration type value is not "000", the CU1 may determine, for example, that the Registration Request received in the process of S105 is not a message used for the initial connection procedure.

[0084] That is, the connection reason of the UE6 is set in the 5GS registration type value. Therefore, when a value other than "000" is set in the 5GS registration type value, the CU1 can determine, for example, that the connection reason of the UE6 has already been set, and can determine that the Registration Request received in the process of S105 is not a message used in the initial connection procedure. On the other hand, when "000" is set in the 5GS registration type value, the CU1 can determine, for example, that the connection reason of the UE6 has not been set, and can determine that the Registration Request received in the process of S105 is a message used in the initial connection procedure.

[0085] Furthermore, when CU1 receives a Registration Request in the process of S105, CU1 may refer to, for example, the first bit of InitialUE-Identity included in the RRC Setup Request received in the process of S103.

[0086] Then, when the first bit of InitialUE-Identity is "1", CU1 may determine that the Registration Request received in the process of S105 is a message used for the initial connection procedure. On the other hand, when the first bit of InitialUE-Identity is "0", CU1 may determine that the Registration Request received in the process of S105 is not a message used for the initial connection procedure.

[0087] That is, InitialUE-Identity is set to randomValue used in the initial connection procedure, or ng-5G-S-TMSI-Part1 which is at least a part of the ID already assigned to UE 6. Then, the leading bit of InitialUE-Identity is set to "0" indicating that randomValue is set in InitialUE-Identity, or to "1" indicating that ng-5G-S-TMSI-Part1 is stored in InitialUE-Identity.

[0088] Therefore, for example, when the first bit of InitialUE-Identity is set to "0", CU1 can determine that the initial connection procedure has not yet been performed for UE 6 that transmitted the Registration Request received in the process of S105, and can determine that the Registration Request received in the process of S105 is a message used for the initial connection procedure. Also, for example, when the first bit of InitialUE-Identity is set to "1", CU1 can determine that the initial connection procedure has already been performed for UE 6 that transmitted the Registration Request received in the process of S105, and can determine that the Registration Request received in the process of S105 is not a message used for the initial connection procedure.

[0089] In addition, when CU1 receives a Registration Request in the processing of S105, it may determine, for example, whether or not the random access procedure performed in the processing of S101 to S104 is a four-step random access procedure and a contention based random access procedure.

[0090] As a result, if the random access procedure performed in the processes from S101 to S104 is not a four-step random access procedure or is not a contention-based random access procedure, the CU1 may determine, for example, that the Registration Request received in the process from S105 is not a message used for the initial connection procedure. On the other hand, if it is determined that the random access procedure performed in the processes from S101 to S104 is a four-step random access procedure and is a contention-based random access procedure, the CU1 may determine, for example, that the Registration Request received in the process from S105 is a message used for the initial connection procedure.

[0091] That is, it can be determined that the random access procedure performed in the initial connection procedure is, for example, a four-step random access procedure and is highly likely to be a contention-based random access procedure. In other words, it can be determined that the random access procedure performed in the initial connection procedure is, for example, a two-step random access procedure or a non-contention-based random access procedure (Contention Free Random Access Procedure). Therefore, for example, when the random access procedure performed in the process from S101 to S104 is not a four-step random access procedure or is not a contention-based random access procedure, CU1 can determine that the Registration Request received in the process from S105 is not a message used for the initial connection procedure. Also, for example, when the random access procedure performed in the process from S101 to S104 is a four-step random access procedure and is a contention-based random access procedure, CU1 can determine that the Registration Request received in the process from S105 is a message used for the initial connection procedure.

[0092] Returning to Figure 12, if it is determined that the Registration Request received in the processing of S105 is not a message used for the initial connection procedure between UE 6 and core network 20, CU1, for example, transmits the Registration Request received in the processing of S105 to AMF 2 (S105-1, NO of S2 in Figure 9, S4 in Figure 9).

[0093] Next, in response to receiving the Registration Request in the process of S105-1, the AMF 2 transmits an Identity Request in the NAS to the UE 6 (S106-1). Then, in response to receiving the Identity Request in the process of S106-1, the UE 6 transmits an Identity Response to the UE 6 (S107-1).

[0094] Next, the AMF 2 transmits an Authentication Request in the NAS in response to receiving an Identity Response in the process of S107-1 (S108-1). Then, the UE 6 transmits an Authentication Response to the UE 6 in response to receiving an Authentication Request in the process of S108-1 (S109-1).

[0095] After that, for example, in response to receiving an Authentication Response in the process of S109-1, the AMF 2 transmits a Security Mode Command in the NAS to the UE 6 (S110-1). Then, for example, in response to receiving a Security Mode Command in the process of S110-1, the UE 6 transmits a Security Mode Complete to the UE 6 (S111-1).

[0096] On the other hand, if it is determined that the Registration Request received in the processing of S105 is a message used for the initial connection procedure between the UE 6 and the core network 20, then the CU1 transmits, for example, the Registration Request received in the processing of S105 to the AMF 3, as shown in FIG. 13 (S105-2, YES in S2 of FIG. 9, S3 of FIG. 9).

[0097] Then, the UE 6 and AMF 3 perform processing of S107-2, S108-2, S109-2, S110-2 and S111-2, in the same manner as, for example, processing of S106-1, S107-1, S108-1, S109-1, S110-1 and S111-1 in FIG. 12.

[0098] Note that, for example, even if it is determined that the Registration Request received in the process of S105 is not a message used for the initial connection procedure, if the UE 6 that transmitted the Registration Request in the process of S105 is an unauthorized terminal device, the CU 1 may transmit the Registration Request received in the process of S105 to the AMF 3. Specifically, for example, even if it is determined that the Registration Request received in the process of S105 is not a message used for the initial connection procedure, if the mobile operator contracted with the UE 6 that transmitted the Registration Request in the process of S105 is different from the mobile operator that owns the core network 20, the CU 1 may transmit the Registration Request received in the process of S105 to the AMF 3.

[0099] [AMF change processing in the first embodiment] Next, a process (hereinafter, also referred to as AMF change process) for changing the AMF for performing a connection procedure (reconnection procedure) with the source UE 6 from AMF3 (initial connection AMF3) to AMF2 (normal processing AMF2) will be described among the communication control processes in the first embodiment. Fig. 14 is a flowchart diagram of the communication control process in the first embodiment.

[0100] As shown in FIG. 14, the AMF change unit 314 waits until the AMF change timing, for example (NO in S31). The AMF change timing may be, for example, the timing at which authentication processing or the like of the message received in the processing of S21 is completed in the processing of S23 described in FIG. 11. That is, the AMF change timing may be, for example, the timing at which the source UE 6 of the message received in the processing of S21 becomes in a state where it can be determined that it is not an unauthorized terminal device. Specifically, the AMF change timing may be, for example, the timing after the processing of S111-2 described in FIG. 13 is performed. Also, the AMF change timing may be, for example, the timing after the processing of S111-2 described in FIG. 13 is performed and further, the connection between the UE 6 and a UPF (User Plane Function) not shown is completed.

[0101] Then, when the AMF change timing arrives (YES in S31), the AMF change unit 314 transmits, for example, information required to perform a connection procedure (reconnection procedure) with the source UE 6 to the AMF 2 (S32).

[0102] That is, for example, when a reconnection procedure between the source UE 6 and the core network 20 is performed, the CU 1 transmits a Registration Request to the AMF 2. Therefore, for example, when the authentication process or the like of the message received in the process of S21 is completed, the AMF change unit 314 transmits information required for performing a connection procedure (reconnection procedure) with the source UE 6 to the AMF 2 in preparation for the reconnection procedure between the source UE 6 and the core network 20.

[0103] As a result, in the communication system 100, it becomes possible to control the AMF 3 to perform authentication processing, etc. in the initial connection procedure with each UE 6, and the AMF 2 to perform other processing (normal processing) including authentication processing, etc. in the reconnection procedure with each UE 6.

[0104] In this manner, the CU1 in the present embodiment receives, for example, the first message transmitted from the UE 6. Then, when the CU1 receives the first message, for example, the CU1 determines whether or not information corresponding to the received first message is information indicating an initial connection procedure between the UE 6 and the core network 20.

[0105] As a result, for example, when CU1 determines that the information corresponding to the received first message is information indicating an initial connection procedure, it transmits the received first message to AMF 2. On the other hand, for example, when CU1 determines that the information corresponding to the first message is not information indicating an initial connection procedure, it transmits the received first message to AMF 3.

[0106] That is, when a DoS attack is carried out against the communication system 10, it can be determined that the UE 6 (unauthorized terminal device) used in the DoS attack is highly likely to perform an initial connection procedure with the core network 20. For this reason, when the CU1 in this embodiment determines that the information corresponding to the first message transmitted from the UE 6 is not information indicating an initial connection procedure, it causes the AMF 2 to perform authentication processing, etc. On the other hand, when the CU1 determines that the information corresponding to the first message transmitted from the UE 6 is information indicating an initial connection procedure, it causes the AMF 3 different from the AMF 2 to perform authentication processing, etc.

[0107] As a result, even if, for example, a DoS attack is carried out and a large amount of first messages are transmitted from an unauthorized terminal device, the communication system 10 in this embodiment can suppress the effect of this attack on the AMF 2. Therefore, even if, for example, a DoS attack is carried out, the communication system 10 can limit the scope of the effect of this attack.

[0108] The above embodiment can be summarized as follows:

[0109] (Appendix 1) A base station device capable of communicating with each of a first communication control device in a network and a second communication control device in the network, a receiving unit that receives a first message transmitted from a terminal device; a processing unit that, when receiving the first message, determines whether or not information corresponding to the received first message is information indicating an initial connection procedure between the terminal device and the network; a transmission unit that transmits the first message to the first communication control device when it is determined that the information corresponding to the first message is information indicating the initial connection procedure, and transmits the first message to the second communication control device when it is determined that the information corresponding to the first message is not information indicating the initial connection procedure. A base station device comprising: (Appendix 2) In Appendix 1: The first message is a Registration Request message in a Non-Access-Stratum protocol (NAS). A base station device comprising: (Appendix 3) In Appendix 1: The first communication control device is an AMF (Access and Mobility Management Function), The second communication control device is another AMF different from the AMF, A base station device comprising: (Appendix 4) In Appendix 1: When the first message includes information indicating that the information corresponds to the initial connection procedure, the processing unit determines that the information corresponding to the first message corresponds to the initial connection procedure. A base station device comprising: (Appendix 5) In Appendix 4: The first message is an RRC Setup Request message. A base station device comprising: (Appendix 6) In Appendix 1: When the random access procedure performed in association with the transmission and reception of the first message is a four-step random access procedure and a contention based random access procedure, the processing unit determines that the information corresponding to the first message is information indicating the initial connection procedure. A base station device comprising: (Appendix 7) In Appendix 1: The first communication control device, When the first message is received, the first message is authenticated; If the authentication of the first message is successful, transmitting information required for authentication of the first message to the second communication control device. A base station device comprising: (Appendix 8) A communication system having a first communication control device in a network, a second communication control device in the network, and a base station device capable of communicating with each of the first communication control device and the second communication control device, The base station device, receiving a first message transmitted from a terminal device; When the first message is received, determining whether or not information corresponding to the received first message is information indicating an initial connection procedure between the terminal device and the network; When it is determined that the information corresponding to the first message is information indicating the initial connection procedure, it transmits the first message to the first communication control device, and when it is determined that the information corresponding to the first message is not information indicating the initial connection procedure, it transmits the first message to the second communication control device; The first communication control device, When the first message is received from the base station device, the first message is authenticated; If the authentication of the first message is successful, transmitting information required for authentication of the first message to the second communication control device. A communication system comprising: (Appendix 9) In Appendix 8: When the random access procedure performed in association with the transmission and reception of the first message is a four-step random access procedure and a contention based random access procedure, the base station device determines that the information corresponding to the first message is information indicating the initial connection procedure. A communication system comprising: (Appendix 10) In Appendix 8: When information indicating that the information corresponding to the first message is information indicating the initial connection procedure is included in the first message, the base station device determines that the information corresponding to the first message is information indicating the initial connection procedure. A communication system comprising: [Explanation of symbols]

[0110] 1:CU 2:AMF 3:AMF 4:DU 5:RU 6:UE 10:RAN 20:Core Network 100: Communication system 101: CPU 102: Memory 103: I / O interface 104: Storage device 105: Bus 130: Information storage area 201: CPU 202: Memory 203: I / O interface 204: Storage device 205: Bus 230: Information storage area 301: CPU 302: Memory 303: I / O interface 304: Storage device 305: Bus 330: Information storage area

Claims

1. A base station device capable of communicating with each of a first communication control device in a network and a second communication control device in the network, a receiving unit that receives a first message transmitted from a terminal device; a processing unit that, when the first message is received, determines whether or not information corresponding to the received first message is information indicating an initial connection procedure between the terminal device and the network; a transmission unit that transmits the first message to the first communication control device when it is determined that the information corresponding to the first message is information indicating the initial connection procedure, and transmits the first message to the second communication control device when it is determined that the information corresponding to the first message is not information indicating the initial connection procedure. A base station device comprising:

2. In claim 1, The first message is a Registration Request message in a Non-Access-Stratum protocol (NAS). A base station device comprising:

3. In claim 1, The first communication control device is an AMF (Access and Mobility Management Function), The second communication control device is another AMF different from the AMF, A base station device comprising:

4. In claim 1, When the first message includes information indicating that the information corresponds to the initial connection procedure, the processing unit determines that the information corresponding to the first message corresponds to the initial connection procedure. A base station device comprising:

5. In claim 4, The first message is an RRC Setup Request message. A base station device comprising:

6. In claim 1, When the random access procedure performed in association with the transmission and reception of the first message is a four-step random access procedure and a contention based random access procedure, the processing unit determines that the information corresponding to the first message is information indicating the initial connection procedure. A base station device comprising:

7. In claim 1, The first communication control device When the first message is received, the first message is authenticated; If the authentication of the first message is successful, transmitting information required for authentication of the first message to the second communication control device. A base station device comprising:

8. A communication system having a first communication control device in a network, a second communication control device in the network, and a base station device capable of communicating with each of the first communication control device and the second communication control device, The base station device, receiving a first message transmitted from a terminal device; When the first message is received, determining whether or not information corresponding to the received first message is information indicating an initial connection procedure between the terminal device and the network; When it is determined that the information corresponding to the first message is information indicating the initial connection procedure, the first message is transmitted to the first communication control device, and when it is determined that the information corresponding to the first message is not information indicating the initial connection procedure, the first message is transmitted to the second communication control device; The first communication control device When the first message is received from the base station device, the first message is authenticated; If the authentication of the first message is successful, transmitting information required for authentication of the first message to the second communication control device. A communication system comprising:

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