MTU Adaptation Control in Core Network Nodes

Abstract

A network management device according to the present invention executes a decision process and an application process. The decision process decides a maximum transmission unit (MTU) value on the basis of information obtained from a reception packet transmitted from a node constituting a wireless access network and received in a core network that integrates a plurality of wireless access networks including the wireless access network constituted by the node. The application process applies the decided MTU value to a transmission packet to be transmitted from the core network to the node.

Description

[Technical field]

[0001] The present disclosure relates to MTU adaptation control in a core network node. [Background technology]

[0002] The mobile network includes a Radio Access Network (RAN) and a Core Network (CN). The RAN nodes are connected to a CN node (hereinafter referred to as the "core") via a backhaul network. For example, in the case of a 5G mobile network, the RAN node is the CU (Central Unit) and the core is the AMF (Access and Mobility Management Function).

[0003] When the CN and RAN constituting a mobile network are owned by one MNO (Mobile Network Operator), the MNO can determine the path MTU (Maximum Transmission Unit) between the core and the RAN node in advance and set an MTU value based on the path MTU in the core. This enables the core to transmit packets to the RAN node with a size as close as possible to the path MTU and not exceeding the path MTU, thereby improving transmission efficiency. Here, the path MTU is the smallest value among the link MTUs from the source to the destination, and is the maximum size of a packet that can be transferred from the source node to the destination node without dividing the packet (fragmentation).

[0004] However, in recent years, in 5G networks (local 5G) operated individually by multiple operators (companies, local governments, etc.), the core functions of the MNO are shared, which is becoming more common. In this case, the core can be connected to each CU of the local 5G-RAN. The core and the CU of the local 5G-RAN are connected by a dedicated line or a VPN (Virtual Private Network), so the path MTU between them is different for each operator. Therefore, the core dynamically detects the path MTU using path MTU discovery technology and transmits packets. As a conventional path MTU discovery technique, for example, Path MTU Discovery for IPv6 is known (see Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] J. McCann et al., "Path MTU Discovery for IP version 6", Internet Engineering Task Force (IETF), RFC8201, July 2017, [online], [Retrieved June 21, 2022], Internet<https: / / datatracker.ietf.org / doc / html / rfc8201> Summary of the Invention [Problem to be solved by the invention]

[0006] In the above conventional path MTU discovery technology, if a packet reaches a route that cannot be forwarded due to an MTU problem, the packet is discarded and an Internet Control Message Protocol (ICMP) error message is sent to the sender from the intermediate node (such as a router) that was unable to forward the packet. This ICMP error message contains the MTU value of the intermediate node that caused the packet to be discarded, and the sender that receives the ICMP error message must adjust the packet size to be equal to or less than the MTU value contained in the ICMP error message and send the packet again. If there are multiple intermediate nodes between the sender and destination, the above process is repeated until the packet sent from the sender reaches the destination. As described above, with conventional path MTU discovery technology, packet transmission processing takes time because ICMP error messages and packet retransmissions may occur.

[0007] It is also possible to set the minimum value of each path MTU determined by discussion between the MNO and each local 5G operator in advance as the MTU value of the core without using the above-mentioned path MTU discovery technology. In this case, the core can transmit packets that do not exceed all path MTUs between each CU. Therefore, the above-mentioned ICMP error message transmission and packet retransmission do not occur, and the processing can be accelerated accordingly. However, the minimum MTU value that does not exceed all path MTUs is applied to all messages sent to each CU. If the MTU value is set small, more packets are required to deliver the same amount of data to the destination. Because a header of a fixed size is added to each packet, the data area in the transmitted packet becomes relatively small, and transmission efficiency decreases. Therefore, it is desirable to set the MTU value as large as possible without exceeding the path MTU.

[0008] Therefore, an object of the present disclosure is to apply an appropriate MTU value in a core network node and further improve packet transmission efficiency. [Means for solving the problem]

[0009] In order to solve the above problems, a network management device according to an embodiment of the present disclosure includes one or more processors. A determination process and an application process are executed by at least one of the one or more processors. The determination process is a process of determining an MTU (Maximum Transmission Unit) value based on information obtained from a received packet transmitted from a node constituting a radio access network and received in a core network that aggregates multiple radio access networks including the radio access network. The application process is a process of applying the MTU value to a packet transmitted from the core network to the node.

[0010] In order to solve the above problems, a network management method according to one embodiment of the present disclosure includes determining an MTU (Maximum Transmission Unit) value based on information obtained from a received packet transmitted from a node constituting a radio access network and received in a core network that aggregates multiple radio access networks including the radio access network, and applying the MTU value to a packet transmitted from the core network to the node.

[0011] In order to solve the above problems, a network management system according to an embodiment of the present disclosure includes one or more processors. A determination process and an application process are executed by at least one of the one or more processors. The determination process is a process of determining an MTU (Maximum Transmission Unit) value based on information obtained from a received packet transmitted from a node constituting a radio access network and received in a core network that aggregates multiple radio access networks including the radio access network. The application process is a process of applying the MTU value to a packet transmitted from the core network to the node. Effect of the Invention

[0012] According to one aspect of the present disclosure, an appropriate MTU value can be applied in a core network node, thereby further improving packet transmission efficiency. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a mobile network equipped with an MNO-RAN. [Diagram 2] FIG. 2 is a diagram illustrating an example configuration of a mobile network equipped with a local 5G-RAN. [Diagram 3] FIG. 3 is an example of a functional block diagram of the core (AMF). [Figure 4] FIG. 4 is an example of a mapping table. [Diagram 5] FIG. 5 is a sequence diagram showing the operation of applying an MTU value based on a RAN attribute. [Figure 6] FIG. 6 is a sequence diagram showing an operation of applying an MTU value based on a UE attribute. [Figure 7] FIG. 7 is a sequence diagram showing the operation of applying the MTU value based on the packet size. [Figure 8] FIG. 8 is a block diagram illustrating an example of a hardware configuration of a network management device. [Figure 9] FIG. 9 is a sequence diagram showing a packet transmission operation to the MNO-RAN. [Figure 10] FIG. 10 is a sequence diagram showing a conventional packet transmission operation to a local 5G-RAN. [Figure 11] FIG. 11 is a sequence diagram showing a conventional packet transmission operation to a local 5G-RAN. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. Among the components disclosed below, those having the same functions are given the same reference numerals, and their description will be omitted. Note that the embodiment disclosed below is one form of the present disclosure, and should be appropriately modified or changed depending on the configuration of the device and various conditions, and is not limited to the following embodiment. In addition, not all of the combinations of features described in this embodiment are necessarily essential to solving the above problem.

[0015] In this embodiment, a fifth generation (5G) mobile network standardized by 3GPP (Third Generation Partnership Project) (registered trademark) is assumed as a network to which the technology according to the present disclosure is applied. Note that the technology according to the present disclosure may be applied to networks other than 5G mobile networks.

[0016] Hereinafter, a case will be described in which the network management device according to this embodiment has an MTU (Maximum Transmission Unit) application control function for applying an MTU (Maximum Transmission Unit) value in a core network node of a 5G mobile network. In this embodiment, a case will be described in which the core network node is an AMF (Access and Mobility Management Function), which is one of the network elements of the 5G core network.

[0017] FIG. 1 is a diagram showing an example of a network configuration of a mobile network 100 to which a network management system according to the present embodiment is applied. The mobile network 100 shown in Fig. 1 includes a Radio Access Network (RAN) to which a user equipment (UE) directly accesses, and a Core Network (CN) that aggregates multiple RANs. In the mobile network 100, the UE and the RAN communicate wirelessly, and the information is sent to the CN for processing. This allows the UE to connect to the Internet or to connect to another company's network to make voice calls. The UE may be a communication terminal capable of mobile communication, such as a smartphone, a tablet terminal, or a personal computer (PC).

[0018] As shown in Fig. 1, the mobile network 100 includes a base station 11 and multiple accommodating stations 12 to 14. Here, the accommodating station 12 is an edge data center, the accommodating station 13 is a regional data center (Regional Data Center: RDC), and the accommodating station 14 is a central data center (Central Data Center: CDC). A backhaul network is formed between the edge data center 12 and the central data center 14. The mobile network 100 in this embodiment may be a virtualized network built on a virtualization platform. In this case, in the mobile network 100, the switching equipment of the backbone network to the wireless access function of the base station can be realized by software on a general-purpose server.

[0019] The base station 11 includes an antenna, a distribution board, a battery, etc. The base station 11 performs the function of a Radio Unit (RU) 220, which is part of the function of the RAN. The edge data center 12 is installed near the base station 11 and is connected to each of the multiple base stations 11 via optical fiber cables or the like. The regional data center 13 is connected to a plurality of edge data centers 12 arranged in a target region. The edge data center 12 or the regional data center 13 performs the functions of a distributed unit (DU) and a central unit (CU) 230, which are part of the RAN functions.

[0020] A central data center (CDC) 14 is connected to multiple edge data centers 12 and multiple regional data centers 13. This central data center 14 performs the functions of a 5G core network. The CDC 10 realizes functions such as the AMF, SMF (Session Management Function), and UPF (User Plane Function) of the 5G core network.

[0021] The number of data centers (accommodation stations) such as the edge data center 12, the regional data center 13, and the central data center 14 is not limited to the number shown in Fig. 1. For example, although only one regional data center 13 and one central data center 14 are shown in Fig. 1, multiple regional data centers 13 and multiple central data centers 14 may be installed.

[0022] In the mobile network 100 shown in FIG. 1, one MNO (Mobile Network Operator) performs end-to-end network management. In the mobile network 100 shown in Fig. 1, the CU 230, which is a RAN node of the MNO-RAN, connects to the AMF 210, which is a core network node. There is a NG Application Protocol (NGAP) standardized by 3GPP as a communication protocol between the CU 230 and the AMF 210, and communication control between the CU 230 and the AMF 210, including establishment of a connection, is performed by transmitting and receiving an NGAP message.

[0023] In this embodiment, in the mobile network 100, the functions of the core network managed by the MNO may be shared by multiple operators (local 5G operators) including companies, local governments, etc. In other words, in the mobile network 100, local 5G-RAN nodes operated by multiple operators may be connected to CN nodes operated by the MNO. That is, the mobile network 100 to which the network management system of the present embodiment is applied may be configured to include a central data center (CDC) 14 and base stations 21 and 22, as shown in Fig. 2. The base stations 21 and 22 are 5G base stations (gNB (gNodeB)) constituting a local 5G-RAN for each operator.

[0024] The base station 21 includes an antenna, a distribution board, a battery, etc. The base station 21 performs the function of a Radio Unit (RU) 220, which is part of the function of the RAN. The base station 22 is installed near the base station 21 and is connected to each of the multiple base stations 21 via optical fiber cables or the like. The base station 22 performs the functions of a distributed unit (DU) and a central unit (CU) 230, which are part of the functions of the RAN.

[0025] Note that the method of dividing the RU, DU, and CU is not limited to the above, and for example, the RU and DU may be placed in base station 21, and the CU may be placed in base station 22. Also, the RU, DU, and CU may be placed together in one base station.

[0026] In the mobile network 100 shown in Fig. 1, one MNO manages the network end-to-end. Since the MNO can know the path MTU between the AMF 210 and the CU 230 in advance, the MNO can set an MTU value in the AMF 210 in advance. For example, if the path MTU between the AMF 210 and the CU 230 of the MNO-RAN is 1500 bytes, the MNO can pre-configure the AMF 210 to have 1500 bytes as the MTU value for communicating with the CU 230.

[0027] Here, the path MTU is the maximum packet size that can be transmitted from a source node (e.g., AMF) to a destination node (e.g., CU) without fragmenting the packet, and is equal to the minimum of the link MTUs in the path from the source node (e.g., AMF) to the destination node (e.g., CU).

[0028] In this case, when the AMF 210 transmits an NGAP message to the CU 230 of the MNO-RAN, the NGAP message can be transmitted with the packet size adjusted to 1500 bytes or less, as shown in step S101 of Fig. 9. As a result, the CU 230 of the MNO-RAN can normally receive the packet transmitted from the AMF 210. In addition, the AMF 210 can transmit a message with a size as close as possible to the path MTU and not exceeding the path MTU. For example, when it is necessary to transmit an NGAP message with a packet size exceeding 1500 bytes, the AMF 210 transmits the NGAP message by performing packet division (fragmentation) into a packet size as close as possible to 1500 bytes and not exceeding 1500 bytes. This can improve data transmission efficiency and effectively utilize network resources.

[0029] On the other hand, the AMF 210 and the CU 230 of the local 5G-RAN are connected by a dedicated line or a VPN (Virtual Private Network), and the path MTU between them is different for each operator. For example, the path MTU between the AMF 210 and the CU 230 of the local 5G-RAN may be 1400 bytes, which is smaller than the path MTU (e.g., 1500 bytes) between the AMF 210 and the CU 230 of the MNO-RAN (MNO backhaul network). Therefore, in the mobile network 100 shown in Fig. 2, even if the AMF 210 transmits a 1500-byte message to the CU 230 of the local 5G-RAN in the same manner as in the case of the CU 230 of the MNO-RAN, the CU 230 cannot directly receive the message. The packet transmission operation in this case is shown in Fig. 10.

[0030] First, in step S111, AMF210 transmits an NGAP message having a packet size of 1500 bytes to CU230 of the local 5G-RAN. When the MTU value supported by an intermediate node such as a router arranged between the CU 230 of the local 5G-RAN and the AMF 210 is 1400 bytes, in step S112, the intermediate node returns an ICMP error message (Too big) indicating that the packet size is too large to the AMF 210. This ICMP error message includes information indicating the MTU value (1400 bytes) supported by the intermediate node.

[0031] Therefore, the AMF 210 divides the packet based on the MTU value included in the ICMP error message, and resends the packet. Specifically, in step S113, AMF210 transmits an NGAP message with a packet size of 1,400 bytes, and in step S114, transmits the remaining NGAP message with a packet size of 100 bytes. This allows the local 5G-RAN CU230 to successfully receive the NGAP message sent from the AMF210. In this case, however, the transmission process takes time because an ICMP error message must be sent and the packet must be retransmitted.

[0032] Therefore, it is conceivable to set the minimum MTU value that does not exceed all path MTUs between each RAN node to the AMF. In this case, the MNO sets the minimum value of the path MTUs between each RAN CU to the AMF 210. This enables the AMF to transmit packets that do not exceed the MTUs of all paths between each CU, so that the transmission of ICMP error messages and retransmission of packets as described above do not occur. Therefore, it is possible to speed up the processing accordingly. However, the smallest MTU value that does not exceed the MTU of any path is applied to all messages sent to each CU, resulting in poor transmission efficiency.

[0033] For example, if AMF210 can connect to an MNO-RAN (path MTU = 1500 bytes) and a local 5G-RAN (path MTU = 1400 bytes), an MTU value of 1400 bytes is pre-configured in AMF210 (step S121 in FIG. 11). Then, when sending an NGAP message of 1500 bytes to the CU 230 of the MNO-RAN, the MTU value = 1400 bytes is applied, and the packet is divided and transmitted (steps S122, 123). In this case, the CU 230 can receive the NGAP message transmitted from the AMF 210 normally.

[0034] In this case, however, a packet that can be transmitted in one go will be divided and transmitted in two to CU 230 of the MNO-RAN, resulting in a decrease in transmission efficiency. In order to utilize network resources more effectively, it is desirable to set the optimal MTU value for each operator (RAN) in the core (AMF). It is also desirable for the MTU value to be set automatically without human intervention.

[0035] Therefore, in this embodiment, the core (AMF) has an MTU application control function that applies an optimal MTU value for each operator (each RAN). Specifically, the AMF 210 receives a packet transmitted from a RAN node, determines an MTU value based on information obtained from the received packet, and automatically applies the determined MTU value to the packet transmitted to the RAN node.

[0036] FIG. 3 is an example of a functional block diagram of the AMF 210. The AMF 210 includes a communication unit 211 , a RAN attribute acquisition unit 212 , an MTU determination unit 213 , an MTU application unit 214 , and a mapping table 215 . The communication unit 211 transmits and receives packets to and from the CU 230. When transmitting a packet to the CU 230, the communication unit 211 adjusts the packet size based on the MTU value applied by the MTU application unit 214 to an MTU value or less corresponding to the RAN (CU) to which the packet is to be transmitted, and transmits the packet.

[0037] The RAN attribute acquisition unit 212 extracts, from a received packet received by the communication unit 211, attribute information relating to the RAN to which the RAN node that is the transmission source of the received packet belongs. Here, the received packet may be, for example, a message transmitted from a RAN node when the RAN or UE connects to a core network. The message may be, for example, a setup request (NG SETUP REQUEST) message transmitted from the CU 230 to the AMF 210, or an NGAP message including a registration request (REGISTRATION REQUEST) message of a Non-Access Stratum (NAS) protocol transmitted from the UE to the AMF 210 via the CU 230.

[0038] Furthermore, the attribute information of a RAN may be any information that can identify the operator that owns (operates) the RAN. The attribute information of the RAN may be, for example, a PLMN (Public Land Mobile Network) number. The PLMN number is an identification number of an operator network that combines an MCC (Mobile Country Number) that indicates a country or region and an MNC (Mobile Network Code) that indicates an operator.

[0039] The MTU determination unit 213 determines an MTU value based on the RAN attribute information acquired by the RAN attribute acquisition unit 212. Specifically, the MTU determination unit 213 derives an MTU value corresponding to the RAN attribute information acquired by the RAN attribute acquisition unit 212, with reference to a mapping table 215 in which the RAN attribute information and the MTU value are associated with each other. The MTU application unit 214 sets the MTU value determined by the MTU determination unit 213 as the MTU value for communicating with the source RAN node of the received packet used to determine the MTU value.

[0040] The mapping table 215 is correspondence information that associates attribute information of a RAN that can be connected to a core network in the mobile network 100 with a path MTU between a node (CU) of the RAN and a node (AMF) of the core network. The MTU determination unit 213 refers to this mapping table 215, derives a path MTU value that corresponds to the attribute information of the RAN acquired by the RAN attribute acquisition unit 212, and determines the derived path MTU value as the above-mentioned MTU value. The mapping table 215 may be created according to an agreement between an operator that owns a core network (in this embodiment, an MNO) and an operator that owns a RAN (in this embodiment, a local 5G operator). Records may be added to the mapping table 215 at any time.

[0041] FIG. 4 is an example of the mapping table 215. The mapping table 215 stores the PLMN number and the MTU value in association with each other. 4 stores 1500 bytes as an MTU value corresponding to an MNO-RAN with a PLMN number of xxxxx. Also, mapping table 215 stores 1450 bytes as an MTU value corresponding to a local 5G-RAN of enterprise A with a PLMN number of yyyyy, and stores 1400 bytes as an MTU value corresponding to a local 5G-RAN of enterprise B with a PLMN number of zzzzz.

[0042] In this embodiment, a case will be described in which the mapping table 215 is stored in an internal memory of the AMF 210, but the mapping table 215 may be managed outside the AMF 210. In this case, the AMF 210 inquires of an external node that manages the mapping table 215 about an MTU value associated with information related to the RAN attribute. Upon receiving the inquiry from the AMF 210, the external node derives an MTU value by referring to the mapping table 215, and transmits the derivation result to the AMF 210. In this case, it becomes possible for one mapping table 215 to be shared by multiple AMFs 210.

[0043] FIG. 5 is a sequence diagram showing the operation of applying an MTU value based on a RAN attribute. When establishing a connection between the RAN (CU) and the core (AMF), first, in step S1, the CU 230 transmits an NGAP setup request message to the AMF 210. This setup request message is "NG SETUP REQUEST" defined in 3GPP TS38.413. The setup request message includes the PLMN number of the RAN to which the CU 230 belongs.

[0044] When the AMF 210 receives the setup request message from the CU 230, the AMF 210 acquires the PLMN number contained in the message. Then, the AMF 210 refers to the mapping table 215 in Fig. 4 and derives the MTU value corresponding to the acquired PLMN number. 5 is a CU belonging to a local 5G-RAN of enterprise A, the setup request message sent by the CU 230 includes PLMN=yyyyy. Therefore, the AMF 210 refers to the mapping table 215 and derives the MTU value=1450. In this case, in step S2, AMF210 applies MTU value=1450 as the MTU value for communicating with CU230.

[0045] Then, in step S3, the AMF 210 transmits a response message (NG SETUP RESPONSE) responding to the setup request message and the subsequent NGAP message to the CU 230. At this time, the AMF 210 recognizes that the maximum size that can be transmitted without dividing a packet in communication with the CU 230 is 1450 bytes, and transmits the NGAP message to the CU 230.

[0046] On the other hand, when the setup request message transmitted from the CU 230 includes PLMN=zzzzz, the AMF 210 refers to the mapping table 215 in Fig. 4 and derives the MTU value=1400. Then, the AMF 210 applies the MTU value=1400 as the MTU value for communicating with the CU 230. In this way, the MTU value=1450 is automatically applied to communication with the CU 230 belonging to the local 5G-RAN of PLMN=yyyyy, and the MTU value=1400 is automatically applied to communication with the CU 230 belonging to the local 5G-RAN of PLMN=zzzzz. In other words, the optimal MTU value for each operator (for each RAN) can be set in the AMF 210.

[0047] In the example shown in Fig. 5, the setup request message includes only one PLMN number, but multiple PLMN numbers may be included. For example, if a base station belongs to both a RAN owned by enterprise A and a RAN owned by enterprise B, the setup request message transmitted by CU 230 included in the base station includes two PLMN numbers. In this case, the AMF 210 derives MTU values ​​corresponding to the two PLMN numbers included in the setup request message, and selects the smaller of the two derived MTU values ​​as the MTU value to be applied. In this way, when a setup request message includes multiple pieces of attribute information, the minimum value of multiple MTU values ​​determined based on the attribute information may be determined as the MTU value to be finally set in the AMF 210. This makes it possible to set an appropriate MTU value even when the base station belongs to multiple RANs operated by different operators.

[0048] FIG. 6 is a sequence diagram showing another example of the operation of applying an MTU value based on a RAN attribute. When registering the UE in the core (AMF), first, in step S11, the UE 240 transmits a NAS registration request message to the AMF 210. This registration request message is a "REGISTRATION REQUEST" defined in 3GPP TS24.501. The registration request message includes the PLMN number of the RAN to which the UE 240 belongs. The NAS registration request message transmitted from the UE 240 is transmitted to the AMF 210 via the CU 230. In step S12, the CU 230 transmits an NGAP message including the NAS registration request message transmitted from the UE 240 to the AMF 210. This NGAP message includes the PLMN number of the RAN to which the UE 240 belongs.

[0049] When the AMF 210 receives the NGAP message from the CU 230, the AMF 210 acquires the PLMN number included in the message. Then, the AMF 210 refers to the mapping table 215 in Fig. 4 and derives the MTU value corresponding to the acquired PLMN number. For example, when the UE 240 shown in FIG. 6 belongs to a local 5G-RAN of the enterprise A, the registration request message sent by the UE 240 includes PLMN=yyyyy. Therefore, the AMF 210 refers to the mapping table 215 and derives the MTU value=1450. In this case, in step S13, AMF210 applies MTU value=1450 as the MTU value for communicating with CU230.

[0050] Then, in step S14, the AMF 210 transmits an NGAP message including a NAS message (REGISTRATION ACCEPT) responding to the registration request message to the CU 230. At this time, the AMF 210 recognizes that the maximum transmittable size of an NGAP message including a NAS message is 1450 bytes, and transmits the NGAP message to the CU 230. In step S15, the CU 230 transmits to the UE 240 a response message to the registration request message.

[0051] As described above, the AMF 210, which is a network management device in this embodiment, receives a packet transmitted from a RAN node, and determines an MTU value based on information obtained from the received packet. Then, the AMF 210 applies the determined MTU value to a packet transmitted from the core network to the RAN node that is the source of the received packet.

[0052] In this way, the AMF 210 can automatically set the MTU value for each RAN node that is the source of the packet. At this time, the AMF 210 determines the MTU value based on information obtained from the received packet, so that it is possible to set an appropriate MTU value for each RAN node. Therefore, in packet transmission from the AMF 210 to the RAN node, efficient transmission processing can be performed without dividing the packet. In other words, it is possible to prevent the transmission of ICMP error messages and the retransmission of packets, which occurs when using the conventional Path MTU Discovery, and to speed up the packet transmission processing. In addition, since an appropriate MTU value can be set for each RAN node and the data payload can be increased, the packet transmission efficiency can be improved.

[0053] Specifically, the AMF 210 may extract attribute information related to the RAN to which the RAN node belongs from the received packet, and determine the MTU value based on the attribute information. Here, the attribute information may be information that can identify the operator that owns the RAN, such as the PLMN. Therefore, in a core network that aggregates multiple RANs (e.g., local 5G-RANs) each owned by a different operator, the AMF 210 can apply an appropriate MTU value for each RAN (CU).

[0054] Furthermore, when determining the MTU value, the AMF 210 uses a mapping table 215 that associates attribute information of a RAN with a path MTU value of the RAN. First, the AMF 210 derives a path MTU value corresponding to the attribute information extracted from the received packet by referring to the mapping table 215. Then, the AMF 210 determines and applies the derived path MTU value as the MTU value for communicating with the RAN (CU). In this way, the MTU value can be easily and appropriately determined by using the mapping table 215. In addition, the MTU value for communicating with each RAN (CU) can be set to the path MTU value between each RAN (CU), so that the packet transmission efficiency can be further improved.

[0055] Here, the received packet may be a setup request message transmitted from a RAN node, or a registration request message transmitted from a UE (communication terminal) via a RAN. In this way, the AMF 210 can determine the MTU value based on a setup request message triggered by the CU 230, which is a RAN node, and transmitted, or a registration request message triggered by the UE 240 and transmitted via the CU 230. Therefore, an appropriate MTU value can be applied to the first transmission packet from the AMF 210 to the CU 230.

[0056] In this embodiment, a case has been described in which the PLMN is used as attribute information of the RAN and the MTU value is derived based on the PLMN, but the information used to derive the MTU value is not limited to the PLMN. For example, the MTU value may be derived using the IMSI (International Mobile Subscriber Identity) of the UE. In this case, the AMF 210 stores a mapping table in which the IMSI range is associated with the MTU value. Here, the IMSI range is a set of IMSIs consisting of one or more IMSIs, and may be, for example, a set of IMSIs assigned to each operator.

[0057] The AMF 210 receives a NAS registration request message transmitted from the UE 240 via the CU 230, and acquires the IMSI of the UE 240 included in the registration request message. Then, the AMF 210 identifies an IMSI range that includes the acquired IMSI, and derives an MTU value corresponding to the identified IMSI range from a mapping table. Here, the registration request message is "REGISTRATION REQUEST" defined in 3GPP TS24.501, and the IMSI is information defined in 3GPP TS23.502.

[0058] In addition, the RAN attribute information used to derive the MTU value may be at least one of the MCC, MNC, TAC (Tracking Area Code), Cell ID, S-NSSAI (Single-Network Slice Selection Assistance Information), and RAN node ID. These pieces of information are notified to the AMF 210 from the CU 230 or the UE 240 by an NGAP message or a NAS message. Furthermore, the attribute information of the RAN used to derive the MTU value may be the IP address of the CU 230 or the IP address range / subnet to which the CU 230 belongs. The AMF 210 can identify the IP address of the CU 230 from the source IP address of the NGAP message. Even when this information is used, it is possible to determine and apply an appropriate MTU value for each RAN (CU).

[0059] In the present embodiment, the AMF 210 derives the MTU value based on information included in a setup request message or a registration request message transmitted when the RAN or the UE connects to the core network. However, the AMF 210 may set the MTU value using the packet size of a packet received from the CU 230. When the AMF 210 normally receives a packet from the CU 230, it can be determined that the path MTU between the AMF 210 and the CU 230 is equal to or larger than the packet size of the received packet. Therefore, the AMF 210 may obtain the packet size of the received packet, and determine the MTU value when transmitting the packet to the CU 230 that is the source of the received packet, based on the obtained packet size. In this case, the AMF 210 can automatically set an MTU value that allows packets to be transmitted without fragmentation, and the mapping table 215 for deriving the MTU value as described above can be eliminated.

[0060] In addition, AMF 210 may store the packet size of a packet received from CU 230 as the MTU value, and each time it receives a packet from the same CU 230, it may compare the stored MTU value with the packet size of the received packet and re-store the larger one as the MTU value. In this way, the maximum packet size of received packets sent from the same RAN node may be determined and applied as the MTU value, making it possible to apply an MTU value close to the path MTU.

[0061] The AMF 210 may store an MTU value for each CU 230 that has a common IP address range or a common subnetwork. In other words, the CUs 230 may be grouped, and the same MTU value may be applied to the CUs 230 that belong to the same group. 8 is a sequence diagram showing the operation of applying the MTU value based on the packet size of a received packet. Here, a case will be described in which the first CU (CU1) 231 and the second CU (CU2) 232 belong to the same subnet (subnet 1).

[0062] First, in step S21, it is assumed that the first CU 231 transmits a 1,200-byte NGAP message to the AMF 210, and the AMF 210 receives the message normally. In this case, in step S22, the AMF 210 applies the packet size of the message, 1200 bytes, as the MTU value for communicating with a CU in the subnetwork 1 to which the first CU 231 belongs. Then, the AMF 210 recognizes that the MTU value is 1200 bytes and transmits an NGAP message to the first CU 231 (step S23). The subnetwork to which the first CU 231 belongs can be identified from the IP address of the first CU 231.

[0063] Then, in step S24, the second CU 232, which belongs to the same subnetwork 1 as the first CU 231, transmits a 1,400-byte NGAP message to the AMF 210, and it is assumed that the AMF 210 successfully receives the message. In this case, the AMF 210 compares the packet size of the packet received from the second CU 232 with the packet size stored as the MTU value for communicating with the CU of subnet 1. The packet size of the packet received from the second CU 232 is larger than the stored MTU value. Therefore, in step S25, the AMF 210 updates the MTU value for communicating with the CU of subnet 1 to 1400, which is the packet size of the received packet. Then, the AMF 210 recognizes that the MTU value is 1400 bytes and transmits an NGAP message to the second CU 232 (step S26).

[0064] Thereafter, in step S27, it is assumed that the AMF 210 receives an NGAP message of 1200 bytes from the first CU 231. In this case, the packet size of the packet received from the first CU 231 is smaller than the packet size stored as the MTU value for communicating with the CU of subnet 1. Therefore, the AMF 210 does not update the stored MTU value. In other words, the MTU value for communicating with the CU of subnet 1 is maintained as 1400 bytes (step S28). Then, the AMF 210 recognizes that the MTU value is 1400 bytes for the first CU 231 and transmits an NGAP message to the first CU 231 (step S29).

[0065] In this way, the MTU value determined based on the packet size of the packet received from the CU 230 may be applied to a packet transmitted from the AMF 210 to a CU 230 in the group to which the CU 230 belongs. Here, the nodes belonging to the same group may be nodes whose IP addresses are included in a predetermined IP address range or nodes belonging to the same subnetwork. By applying a common MTU value to the grouped CUs 230, as in the example shown in Fig. 7, even if the first CU 231 has only transmitted a 1200-byte message, the MTU value can be recognized as 1400 bytes and the message can be sent back. This improves packet transmission efficiency. In addition, since the CUs 230 are grouped by IP address range or subnetwork, the CUs 230 belonging to the RAN owned by the same operator can be grouped and a common MTU value can be applied to the CUs 230. Therefore, the MTU value for communication with each CU 230 can be appropriately set.

[0066] As described above, in this embodiment, an appropriate MTU value can be applied in a core network node without changing the standard specifications, thereby making it possible to further improve packet transmission efficiency.

[0067] In the above embodiment, the mobile network 100 includes a CN owned by an MNO and a RAN owned by a local 5G operator. However, the mobile network 100 may include a CN owned by a local 5G operator or another operator, and a RAN owned by an MNO or another operator.

[0068] Furthermore, in the above embodiment, the case where the mobile network 100 is a 5G mobile network has been described, but the mobile network 100 may be a 4G mobile network. That is, the above-mentioned operation of the AMF 210 can also be applied to the operation of an MME (Mobility Management Entity) constituting a 4G core network. When applied to a 4G mobile network, the AMF should be replaced with the MME, the CU with a BBU (Base Band Unit), the gNB (gNodeB) with an eNB (eNodeB), and the NGAP with the S1AP. Moreover, the mobile network 100 is not limited to a 5G mobile network or a 4G mobile network, and may be a mobile network after 5G, such as a sixth generation (6G) mobile network.

[0069] The network management device according to this embodiment may be implemented in any general-purpose server constituting the core network of the mobile network 100. The network management device may also be implemented in a dedicated server. The network management device may also be implemented on a single computer or multiple computers. When the network management device is implemented in a single computer, as shown in Fig. 8, the network management device 1 may include a CPU 2, a ROM 3, a RAM 4, a HDD 5, an input unit (keyboard, pointing device, etc.) 6, a display unit (monitor, etc.) 7, a communication I / F 8, etc. The network management device 1 may also include an external memory.

[0070] The CPU 2 is configured with one or more processors, and performs overall control of the operations in the network management device 1. At least some of the functions of each element shown in Fig. 3 can be realized by the CPU 2 executing a program. Note that the program may be stored in a non-volatile memory such as the ROM 3 or the HDD 5, or in an external memory such as a removable storage medium (not shown).

[0071] 3 may be configured to operate as dedicated hardware. In this case, the dedicated hardware operates under the control of the CPU 2. For functions that are realized by hardware, for example, a specific compiler may be used to automatically generate a dedicated circuit on an FPGA from a program for realizing the function of each functional module. Alternatively, a gate array circuit may be formed in the same manner as an FPGA to realize the functions as hardware. Alternatively, the functions may be realized by an ASIC (Application Specific Integrated Circuit).

[0072] Aspects of the present disclosure may include a computer-readable storage medium storing a program, where the program includes instructions that, when executed by a CPU 2 (at least one of one or more processors) of the network management device 1, cause the network management device 1 to perform at least any of the methods described above.

[0073] Although specific embodiments have been described above, the embodiments are merely illustrative and are not intended to limit the scope of the present disclosure. The devices and methods described herein can be embodied in forms other than those described above. Furthermore, the above-described embodiments can be appropriately omitted, substituted, and modified without departing from the scope of the present disclosure. Such omitted, substituted, and modified forms are included in the scope of the claims and their equivalents, and belong to the technical scope of the present disclosure.

[0074] (Embodiments of the present disclosure) The present disclosure includes the following embodiments. [1] A network management device comprising one or more processors, wherein at least one of the one or more processors executes a determination process for determining an MTU (Maximum Transmission Unit) value based on information obtained from a received packet transmitted from a node constituting a radio access network and received in a core network that aggregates multiple radio access networks including the radio access network, and an application process for applying the MTU value to a packet transmitted from the core network to the node.

[0075] [2] The network management device described in [1], wherein the determination process extracts attribute information regarding the wireless access network to which the node belongs from the received packet, and determines the MTU value based on the attribute information.

[0076] [3] The network management device described in [2] is characterized in that the determination process derives the path MTU value corresponding to the attribute information extracted from the received packet by referring to a mapping table that corresponds attribute information regarding the radio access network with a path MTU value between a node of the radio access network and a node of the core network, and determines the derived path MTU value as the MTU value.

[0077] [4] A network management device according to [2] or [3], characterized in that the received packet is a setup request message sent from the node.

[0078] [5] A network management device according to [2] or [3], characterized in that the received packet is a registration request message transmitted from a communication terminal via the wireless access network.

[0079] [6] A network management device according to any one of [2] to [5], characterized in that the attribute information is information capable of identifying an operator that owns the wireless access network.

[0080] [7] A network management device according to any one of [2] to [6], characterized in that the attribute information includes at least one of PLMN (Public Land Mobile Network), MCC (Mobile Country Number), MNC (Mobile Network Code), IMSI (International Mobile Subscriber Identity), TAC (Tracking Area Code), Cell ID, S-NSSAI (Single-Network Slice Selection Assistance Information), radio access network node ID and IP address.

[0081] [8] A network management device described in any of [2] to [7], characterized in that, when multiple attribute information is extracted from the received packet, the determination process determines the minimum of the MTU values ​​determined based on the multiple attribute information as the final MTU value.

[0082] [9] A network management device according to any one of [1] to [8], characterized in that the determination process obtains the packet size of the received packet and determines the MTU value based on the packet size.

[0083]

[10] The network management device described in [9], wherein the determination process determines the maximum packet size of the received packets sent from the same node as the MTU value.

[0084]

[11] A network management device as described in [9] or

[10] , characterized in that the application process applies the MTU value to packets transmitted from the core network to nodes in the group to which the node belongs.

[0085]

[12] The network management device described in

[11] , wherein the application process determines that nodes whose IP addresses are included in a specified IP address range or nodes that belong to the same subnetwork are nodes that belong to the same group.

[0086]

[13] A network management method comprising: determining an MTU (Maximum Transmission Unit) value based on information obtained from a received packet transmitted from a node constituting a radio access network and received in a core network that aggregates multiple radio access networks including the radio access network; and applying the MTU value to a packet transmitted from the core network to the node.

[0087]

[14] A network management system comprising one or more processors, wherein at least one of the one or more processors executes a determination process for determining an MTU (Maximum Transmission Unit) value based on information obtained from a received packet transmitted from a node constituting a radio access network and received in a core network that aggregates multiple radio access networks including the radio access network, and an application process for applying the MTU value to a packet transmitted from the core network to the node. [Explanation of symbols]

[0088] 11...base station, 12...edge data center, 13...regional data center (RDC), 14...central data center (CDC), 21, 22...base station, 100...mobile network, 210...AMF, 211...communication unit, 212...RAN attribute acquisition unit, 213...MTU determination unit, 214...MTU application unit, 215...mapping table, 220...RU, 230...CU, 240...UE

Claims

1. one or more processors; by at least one of the one or more processors, A process of determining a maximum transmission unit (MTU) value based on information obtained from a received packet transmitted from a node constituting a radio access network and received in a core network aggregating a plurality of radio access networks including the radio access network; applying the MTU value to packets sent from the core network to the node; is executed, A network management device comprising:

2. The determination process extracts attribute information related to the radio access network to which the node belongs from the received packet, and determines the MTU value based on the attribute information.

2. The network management device according to claim 1.

3. The determination process refers to a mapping table that associates attribute information related to the radio access network with a path MTU value between a node of the radio access network and a node of the core network, derives the path MTU value corresponding to the attribute information extracted from the received packet, and determines the derived path MTU value as the MTU value.

3. The network management device according to claim 2.

4. The received packet is a setup request message sent from the node.

3. The network management device according to claim 2.

5. The received packet is a registration request message transmitted from a communication terminal via the wireless access network.

3. The network management device according to claim 2.

6. The attribute information is information capable of identifying a carrier that owns the wireless access network.

3. The network management device according to claim 2.

7. The attribute information includes at least one of a Public Land Mobile Network (PLMN), a Mobile Country Number (MCC), a Mobile Network Code (MNC), an International Mobile Subscriber Identity (IMSI), a Tracking Area Code (TAC), a Cell ID, a Single-Network Slice Selection Assistance Information (S-NSSAI), a Radio Access Network Node ID, and an IP address.

3. The network management device according to claim 2.

8. When a plurality of pieces of attribute information are extracted from the received packet, the determination process determines a minimum value of the MTU values ​​determined based on the plurality of pieces of attribute information as the final MTU value.

3. The network management device according to claim 2.

9. The determination process obtains a packet size of the received packet, and determines the MTU value based on the packet size.

2. The network management device according to claim 1.

10. The determination process determines the maximum value of the packet size of the received packets transmitted from the same node as the MTU value.

10. The network management device according to claim 9.

11. The application process applies the MTU value to a packet transmitted from the core network to a node in a group to which the node belongs.

10. The network management device according to claim 9.

12. The application process determines that nodes whose IP addresses are included in a predetermined IP address range or that belong to the same subnetwork are nodes that belong to the same group.

12. The network management device according to claim 11.

13. A network management method executed by a network management device, comprising: determining a maximum transmission unit (MTU) value based on information obtained from a received packet transmitted from a node constituting a radio access network and received in a core network aggregating a plurality of radio access networks including the radio access network; applying the MTU value to packets transmitted from the core network to the node; 23. A network management method comprising:

14. one or more processors; by at least one of the one or more processors, A process of determining a maximum transmission unit (MTU) value based on information obtained from a received packet transmitted from a node constituting a radio access network and received in a core network aggregating a plurality of radio access networks including the radio access network; applying the MTU value to packets sent from the core network to the node; is executed, A network management system comprising:

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