Communication device, communication system, and signal transfer method

Abstract

A communication device including a duplication unit that, when a switching condition for switching the transfer destination of a signal is satisfied, duplicates transfer data to be transferred, and transfers the duplicated transfer data to a switching source communication device that is a switching source and a switching destination communication device that is a switching destination.

Description

Communication device, communication system, and signal transfer method

[0001] The present invention relates to a communication device, a communication system, and a signal transfer method.

[0002] When multiple communication devices communicate simultaneously, such as when multiple upper devices and multiple lower devices communicate with each other, congestion can occur, resulting in communication delays. Congestion can sometimes be resolved by switching the communication path (hereinafter referred to as "path switching") using a transfer device installed on the communication path, thereby changing the connection relationship between the upper device and the lower device. If communication traffic (hereinafter referred to as "traffic") concentrated on a specific communication device (e.g., an upper device) can be distributed to multiple communication devices by path switching, congestion can be resolved, and communication delays can be reduced.

[0003] Conventionally, in a communication system having a transfer device that can change the connection relationship between a higher-level device and a lower-level device, there is a technology that collects information indicating the amount of traffic measured by the higher-level device and the lower-level device (hereinafter referred to as "traffic volume"), determines whether congestion has occurred at the offload destination based on the collected traffic volume, and performs route switching (see, for example, Patent Document 1).

[0004] International Publication No. 2023 / 181139

[0005] Conventional communication systems predict traffic volume in advance and switch routes based on the predicted results before congestion occurs. When switching routes, switching control instructions are sent to the upper device, lower device, and forwarding device, and sequences for establishing communication and changing routes are executed. This has led to problems such as switching delays and packet loss during route switching.

[0006] In view of the above circumstances, an object of the present invention is to provide a technique capable of suppressing faults such as switching delays and packet loss when switching routes.

[0007] One aspect of the present invention is a communication device that includes a duplication unit that, when a switching condition for switching the destination of a signal is met, copies transfer data to be transferred and transfers the copied transfer data to a source communication device that is the source of the switching and a destination communication device that is the destination of the switching.

[0008] One aspect of the present invention is a communication system comprising a first communication device, a plurality of second communication devices that communicate with the first communication device, and a control device, wherein the plurality of second communication devices are a second communication device that is a switching source and a second communication device that is a switching destination, and when a switching condition for switching the destination of a signal is met, the control device notifies the first communication device, the second communication device that is the switching source, and the second communication device that is the switching destination that the switching condition has been met, and the first communication device has a copying unit that copies the transfer data to be transferred when the notification is received from the control device, and transfers the copied transfer data to the second communication device that is the switching source and the second communication device that is the switching destination.

[0009] One aspect of the present invention is a signal transfer method that, when a switching condition for the signal transfer destination is met, copies transfer data to be transferred and transfers the copied transfer data to a switching source communication device that is the source of the transfer and a switching destination communication device that is the destination of the transfer.

[0010] The present invention makes it possible to suppress problems such as switching delays and packet loss when switching routes.

[0011] FIG. 1 is a diagram showing the configuration of a communication system which is an example of a conventional communication system. FIG. 2 is a diagram showing the configuration of a mobile communication system which is an example of a conventional communication system. FIG. 3 is a sequence diagram showing the flow of route switching processing in a conventional mobile communication system. FIG. 4 is a diagram showing an example configuration of a communication system in an embodiment. FIG. 5 is a diagram showing a first example configuration of a duplication unit in an embodiment. FIG. 6 is a diagram showing a second example configuration of a duplication unit in an embodiment. FIG. 7 is a sequence diagram showing the flow of processing in a communication system in an embodiment. FIG. 8 is a sequence diagram showing the flow of route switching processing performed by a communication system in an embodiment. FIG. 9 is a diagram showing an example configuration of a communication system in a modified example of an embodiment.

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each embodiment, components having the same function are denoted by the same reference numerals, and repeated description of the functions may be omitted.

[0013] FIG. 1 is a diagram showing the configuration of a communication system 1, which is an example of a conventional communication system. The communication system 1 has a plurality of lower-level devices 3, a plurality of upper-level devices 4, and a switching instruction device 7. The lower-level devices 3 and the upper-level device 4 are connected via a network 5. The network 5 includes one or more transfer devices (not shown; devices corresponding to the transfer device 15 shown in FIG. 2, which will be described later). The transfer device also functions as a switching device that can change the connection relationship between the lower-level devices 3 and the upper-level device 4.

[0014] 1, the four lower devices 3 are respectively referred to as lower devices 3-1 to 3-4, and the two upper devices 4 are respectively referred to as upper devices 4-1 and 4-2. Hereinafter, the direction from the lower device 3 to the upper device 4 will be referred to as "upstream," and the direction from the upper device 4 to the lower device 3 will be referred to as "downstream."

[0015] The lower device 3 transmits an upstream signal to the connected upper device 4. The network 5 transfers the upstream signal to the upper device 4 according to the communication path between the lower device 3 and the upper device 4. The upper device 4 also transmits a downstream signal to the connected lower device 3. The network 5 transfers the downstream signal to the lower device 3 according to the communication path between the lower device 3 and the upper device 4. The switching instruction device 7 instructs each device, such as a transfer device, to switch the communication path.

[0016] The switching instruction device 7 uses information such as traffic volume or traffic allocation volume (hereinafter collectively referred to as "traffic volume") acquired from the lower-level device 3 and the upper-level device 4 to predict in advance the traffic volume of some or all communication links (hereinafter simply referred to as "links" or "flows") in the communication path between the lower-level device 3 and the upper-level device 4. The switching instruction device 7 determines a switching threshold for each link based on the traffic volume prediction accuracy and the transmission capacity of the link.

[0017] For example, the link rate can be used as an index representing the transmission capacity of a link. The link rate is the maximum communication speed of the link. The switching threshold is a threshold used to determine whether congestion requiring a switch of the communication path (route switching) is predicted to occur. For example, even for the same link rate, the switching instruction device 7 determines a lower switching threshold as the prediction accuracy of the traffic volume becomes lower.

[0018] The switching instruction device 7 determines whether congestion will occur for each link using the predicted traffic volume and a switching threshold. If congestion is predicted to occur in any link, the switching instruction device 7 determines to perform path switching for load balancing. The switching instruction device 7 instructs switching of communication paths (path switching) so that at least a portion of the traffic transmitted through a link predicted to be congested is transmitted through a link predicted not to be congested. This enables optimal communication path switching according to prediction accuracy. Furthermore, link congestion delays are reduced, enabling higher bandwidth utilization efficiency.

[0019] As shown in FIG. 1 , the switching instruction device 7 includes a prediction unit 71, a switching threshold determination unit 72, and a switching determination unit 75. The prediction unit 71 acquires prediction information from each device to be used for predicting the traffic volume of each link. The prediction information includes, for example, the traffic volume observed by the device, the traffic allocation volume to the device, the number of terminals connected to the device, and communication quality. The prediction unit 71 predicts the future traffic volume for each link using the prediction information. Any existing technology can be used to predict the future traffic volume.

[0020] The switching threshold determination unit 72 includes a prediction accuracy calculation unit 73 and a threshold calculation unit 74. The prediction accuracy calculation unit 73 calculates prediction accuracy for each link based on past prediction results of future traffic volume and actual traffic volume. The threshold calculation unit 74 determines a switching threshold for each link such that the ratio to the link's transmission capacity (e.g., link rate) becomes lower as the prediction accuracy becomes lower.

[0021] The switching determination unit 75 determines in advance whether congestion will occur for each link using the predicted future traffic volume value and a switching threshold. If congestion is predicted, the switching determination unit 75 determines to perform route switching for load balancing. For example, the switching determination unit 75 determines to perform route switching from a link where congestion is predicted to occur to a link with a lower link utilization rate. The switching determination unit 75 instructs each device to perform processing for route switching.

[0022] An example in which the communication system 1 is applied to a mobile communication system will be described below.

[0023] 2 is a diagram showing the configuration of a mobile communication system 10, which is an example of a conventional communication system. The mobile communication system 10 is an example of the communication system 1. The mobile communication system 10 is, for example, a fifth-generation mobile communication system (5G). The mobile communication system 10 includes a plurality of terminal stations 11, a plurality of antenna stations 12, a plurality of remote stations 13, a plurality of central stations 14, a transfer device 15, a switching instruction device 17, and a resource allocation device 16.

[0024] The terminal station 11, the antenna station 12, the distributed station 13, and the central station 14 are UE (User Equipment), RU (Radio Unit), DU (Distributed unit), and CU (Central unit), respectively, of a fifth-generation mobile communication system. The distributed station 13 is an example of a lower-level device 3, and the central station 14 is an example of a higher-level device 4. However, the combination of a device corresponding to the lower-level device 3 and a device corresponding to the higher-level device 4 is not limited to the combination of the distributed station 13 and the central station 14, and is arbitrary. The transfer device 15 is an example of a transfer device that constitutes the network 5.

[0025] The transfer device 15 also functions as a switching device that can change the connection relationship between the remote stations 13 and the central station 14. The transfer function and the switching function of the transfer device 15 may be realized by separate devices. The switching instruction device 17, the transfer device 15, the resource allocation device 16, and other devices do not necessarily need to be separate devices, and may be configured as an integrated device.

[0026] The mobile communication system 10 is connected to an upper network 20. Here, the M (M is an integer equal to or greater than 1) remote stations 13 are referred to as remote stations 13-1 to 13-M, respectively. Furthermore, the Km (Km is an integer equal to or greater than 1) antenna stations 12 subordinate to the remote station 13-m (m is an integer equal to or greater than 1 and equal to or less than M) are referred to as antenna stations 12-m, respectively. Furthermore, the N (N is an integer equal to or greater than 2) central stations 14 are referred to as central stations 14-1 to 14-N, respectively. Therefore, the mobile communication system 10 shown in FIG. 2 is an example of a mobile communication system in which M=4, K1=2, K2=2, K3=2, K4=2, and N=2.

[0027] The terminal station 11 transmits and receives radio signals to and from the antenna station 12 using radio resources allocated by the remote station 13. The allocated radio resources include information indicating the start and end timings of time periods during which radio signal transmission and reception are permitted. The start and end timings are represented by, for example, slots. A slot is a unit of scheduling for data transmission and reception in a radio frame. The allocated radio resources may further include information indicating a coding rate and a modulation method.

[0028] The antenna station 12 receives uplink data from the terminal station 11 via a wireless signal. The antenna station 12-m sets the received uplink data as an uplink signal and transmits the uplink signal to the remote station 13-m via a wired interface. The antenna station 12-m also receives a downlink signal from the remote station 13-m via a wired interface. The antenna station 12 transmits the downlink data addressed to the terminal station 11, which is set in the received downlink signal, to the terminal station 11 via a wireless signal.

[0029] The remote station 13-m receives uplink signals from each of the Km antenna stations 12-m. The uplink signals received by the remote station 13-m include uplink data received by the antenna station 12-m from the terminal stations 11 under its control. The remote station 13 generates an uplink signal that aggregates the uplink data and transmits the generated uplink signal to the central station 14 to which the remote station 13 is connected. The remote station 13 also receives a downlink signal from the central station 14 to which the remote station 13 is connected, in which downlink data addressed to the terminal stations 11 under its control is set. The remote station 13-m converts the received downlink signal into a downlink signal corresponding to the radio signal to be transmitted from each antenna station 12-m. The remote station 13-m transmits the converted downlink signal to the antenna station 12-m corresponding to the downlink signal.

[0030] The central station 14 aggregates the uplink signals received from the subordinate remote stations 13 and transfers them to the upper network 20. The central station 14 also receives downlink signals from the upper network 20, in which downlink data addressed to the terminal stations 11 is set, and transfers the received downlink signals to the remote stations 13 connected to the destination terminal stations 11.

[0031] The transfer device 15 is connected to the remote stations 13, the central station 14, and the switching instruction device 17. The transfer device 15 is an example of a switching device that switches (switches) communication paths. The transfer device 15 transfers signals along the communication path between the remote stations 13 and the central station 14. That is, the transfer device 15 transfers upstream signals received from the remote stations 13 to the destination central station 14 along the communication path. The transfer device 15 also transfers downstream signals received from the central station 14 to the destination remote station 13 along the communication path. The transfer of signals along the communication path is performed under instructions from the switching instruction device 17. The resource allocation device 16 manages the resources of the central station 14.

[0032] The switching instruction device 17 is connected to the remote station 13, the central station 14, and the transfer device 15. The switching instruction device 17 may further be connected to the resource allocation device 16. The switching instruction device 17 instructs the transfer device 15 (switching device) to switch the communication path between the remote station 13 and the central station 14. In the mobile communication system 10, the communication path between the remote station 13 and the central station 14 is determined based on the connection relationship between the remote station 13 and the central station 14. Therefore, in the mobile communication system 10, the path between the remote station 13 and the central station 14 is switched by controlling the transfer device 15 (switching device) to change the central station 14 to which the remote station 13 is connected.

[0033] Also, as an example, it is assumed here that the switching instruction device 17 of the mobile communication system 10 determines, based on the upstream traffic, whether or not congestion has occurred on the central station 14 side, which corresponds to the higher-level device 4. Therefore, unless otherwise specified, traffic in the following description refers to the traffic of upstream signals.

[0034] Fig. 3 is a sequence diagram showing the flow of a route switching process in a conventional mobile communication system 10. Fig. 3 shows, as an example, switching of the central station 14. In the following description, it is assumed that the DU 13-1 in Fig. 3 corresponds to the remote station 13-1 in Fig. 2, the Source CU 14-1 corresponds to the central station 14-1 in Fig. 2, and the Target CU 14-2 corresponds to the central station 14-2 in Fig. 2.

[0035] Assume that a trigger for path switching occurs in Source CU 14-1, which is the connection destination of DU 13-1 (step S1). The C-Plane of Source CU 14-1 transmits a BEARER CONTEXT SETUP REQUEST to Target CU 14-2 (step S2). The BEARER CONTEXT SETUP REQUEST is a request signal for requesting the establishment of a new bearer. Target CU 14-2 receives the BEARER CONTEXT SETUP REQUEST transmitted from Source CU 14-1. Target CU 14-2 transmits a BEARER CONTEXT SETUP RESPONSE to Source CU 14-1 (step S3). The BEARER CONTEXT SETUP RESPONSE is a response signal to the BEARER CONTEXT SETUP REQUEST.

[0036] Thereafter, Source CU 14-1 notifies terminal stations 11 connected to DU 13-1 of the bearer change via DU 13-1 (step S4). The C-Plane of Source CU 14-1 sends a BEARER CONTEXT MODIFICATION REQUEST to the U-Plane of Source CU 14-1 (step S5). The BEARER CONTEXT MODIFICATION REQUEST is a request signal for requesting a bearer change. The U-Plane of Source CU 14-1 receives the BEARER CONTEXT MODIFICATION REQUEST sent from the C-Plane of Source CU 14-1. The U-Plane of Source CU 14-1 transmits a BEARER CONTEXT MODIFICATION RESPONSE to the C-Plane of Source CU 14-1 (step S6). The BEARER CONTEXT MODIFICATION RESPONSE is a response signal to the BEARER CONTEXT MODIFICATION REQUEST.

[0037] Furthermore, the C-Plane of Source CU 14-1 transmits a BEARER CONTEXT MODIFICATION REQUEST to Target CU 14-2 (step S7). Target CU 14-2 receives the BEARER CONTEXT MODIFICATION REQUEST transmitted from the C-Plane of Source CU 14-1. Target CU 14-2 transmits a BEARER CONTEXT MODIFICATION RESPONSE to the C-Plane of Source CU 14-1 (step S8).

[0038] After the above steps S1 to S8 are executed, downstream traffic is transferred in the following order: AMF / UPF → Source CU14-1 → Target CU14-2 → DU13-1 (step S9). On the other hand, upstream traffic is transferred in the following order: DU13-1 → Source CU14-1 → AMF / UPF. In other words, at this point, upstream traffic is transferred to the upper network without passing through Target CU14-2.

[0039] The Source CU 14-1 instructs the AMF / UPF to forward downstream traffic directly to the Target CU 14-2. The AMF / UPF updates the path in response to the instruction from the Source CU 14-1 (step S10). The AMF / UPF sends an End marker to the Source CU 14-1 (step S11). The Source CU 14-1 then sends the End marker sent from the AMF / UPF to the Target CU 14-2, thereby notifying the end of traffic forwarding on the old route. The AMF / UPF then establishes a new path between the Target CU 14-2 and the Source CU 14-1 (step S12). As a result, downstream traffic sent from the AMF / UPF is forwarded to the DU 13-1 via the Target CU 14-2.

[0040] The C-Plane of Source CU 14-1 transmits a BEARER CONTEXT REALEASE COMMAND to the U-Plane of Source CU 14-1 (step S13). The BEARER CONTEXT REALEASE COMMAND is a request signal for instructing the deletion of the old bearer. The U-Plane of Source CU 14-1 receives the BEARER CONTEXT REALEASE COMMAND transmitted from the C-Plane of Source CU 14-1. The U-Plane of Source CU 14-1 transmits a BEARER CONTEXT REALEASE COMPLETE to the C-Plane of Source CU 14-1 (step S14). BEARER CONTEXT RELEASE COMPLETE is a signal to notify that the deletion of the old bearer has been completed.

[0041] As described above, when a trigger occurs in Source CU 14-1, the higher-level connection is first changed, and the downlink connection is changed to the switching destination CU (Target CU 14-2). After that, upon receiving BEARER CONTEXT RELEASE COMPLETE, the uplink connection is changed to the switching destination CU (Target CU 14-2). Therefore, a time lag occurs between the downlink switching and the uplink switching. When the path switching is performed in accordance with the downlink, a section occurs where uplink traffic cannot be transmitted, resulting in packet loss and switching delays. Furthermore, when the path switching is performed in accordance with the uplink, downlink packet loss and switching delays occur. Therefore, the present invention solves these problems. A specific configuration of the present invention is described below.

[0042] Fig. 4 is a diagram showing an example of the configuration of a communication system 100 according to an embodiment. The communication system 100 includes a first communication device 30, a plurality of second communication devices 40, a control device 50, and a subsequent device 60. Although Fig. 4 shows a configuration in which the communication system 100 includes one first communication device 30, two second communication devices 40-1 and 40-2, and one subsequent device 60, the number of these devices is not particularly limited.

[0043] The communication system 100 may include at least a plurality of second communication devices 40. Hereinafter, the second communication device 40-1 is the device from which switching is performed, and the second communication device 40-2 is the device to which switching is performed. In addition, the following explanation will be given taking route switching based on upstream traffic as an example.

[0044] The first communication device 30 and each second communication device 40, and each second communication device 40 and subsequent device 60 are connected via optical transmission paths. The optical transmission paths are optical fibers. The optical transmission paths may be provided with one or more optical amplifiers that amplify optical signals. The first communication device 30 and the control device 50, and each second communication device 40 and the control device 50 are connected via control lines (electrical lines) for transmitting and receiving information.

[0045] The first communication device 30 forwards traffic transmitted from a connected user terminal or a core network to the second communication device 40, which is the forwarding destination. For example, the first communication device 30 forwards traffic to the second communication device 40-1 to which it is connected until it becomes necessary to switch the path.

[0046] The first communication device 30 forwards traffic to both the second communication device 40-1 and the second communication device 40-2 from the time when the switching conditions are satisfied until the path switching is completed. That is, the first communication device 30 forwards traffic to both the second communication device 40-1, which is the source of switching, and the second communication device 40-2, which is the destination of switching, from the time when the switching conditions are satisfied until the path switching is completed. Hereinafter, the forwarding of traffic by the first communication device 30 to both the second communication device 40-1, which is the source of switching, and the second communication device 40-2, which is the destination of switching, may also be referred to as redundant forwarding. The first communication device 30 is, for example, a DU in the 5G communication standard.

[0047] The switching condition here refers to a condition that requires switching of the signal forwarding destination. The switching condition may be, for example, that a switching notification is received from the control device 50, that a handover is required, or that a switching instruction is received from the second communication device 40.

[0048] The second communication device 40 receives traffic forwarded from the first communication device 30 and processes it or forwards it to the subsequent device 60. Furthermore, the second communication device 40 forwards traffic transmitted from the subsequent device 60 to the first communication device 30. The second communication device 40 is, for example, a CU in a 5G communication standard.

[0049] The control device 50 controls the path switching between the first communication device 30 and the second communication device 40. For example, the control device 50 collects traffic information from the first communication device 30, and controls the path switching between the first communication device 30 and the second communication device 40 based on the collected traffic information.

[0050] The subsequent device 60 receives traffic forwarded from at least one of the second communication device 40-1 or the second communication device 40-2 and processes the traffic or forwards the traffic to another network. The subsequent device 60 is, for example, a UPF (User Plane Function) in the 5G communication standard.

[0051] Next, the functional configuration of each device will be described in detail.

[0052] (Functional configuration of first communication device 30) The first communication device 30 includes an information processing unit 31 and a duplication unit 32. The information processing unit 31 acquires traffic transmitted from a connected user terminal or from the core network. The information processing unit 31 outputs the acquired traffic to the duplication unit 32. The information processing unit 31 also outputs load information to the control device 50. The load information is information related to the load on the first communication device 30, such as traffic information, the number of newly connected terminals, the number of terminals for each QoS (Quality of Service), and the usage rate or traffic volume of a CPU (Central Processing Unit).

[0053] The duplicating unit 32 duplicates the traffic output from the information processing unit 31 and transfers it to at least one of the second communication device 40-1, which is the switching source, or the second communication device 40-2, which is the switching destination. The duplicating unit 32 transfers the traffic to the second communication device 40-1, which is the switching source, based on the header information of the traffic, during the period until the switching condition is satisfied. In other words, even if the duplicating unit 32 duplicates the traffic, it does not transfer the traffic to the second communication device 40-2, which is the switching destination, during the period until the switching condition is satisfied.

[0054] The duplicator 32 duplicates traffic from the time when the switching condition is satisfied until the path switching is completed, and transfers the duplicated traffic to both the second communication device 40-1, which is the switching source, and the second communication device 40-2, which is the switching destination. Information indicating the second communication device 40-2, which is the switching destination, may be notified from the control device 50. Completion of the path switching may be the completion of the processing of step S14 in FIG. 3.

[0055] After the path switching is completed, the duplicating unit 32 transfers the copied traffic to the second communication device 40-2, which is the switching destination. In other words, after the path switching is completed, even if the duplicating unit 32 has copied the traffic, it does not transfer the traffic to the second communication device 40-1, which is the switching source.

[0056] The duplicating unit 32 can duplicate traffic in two ways: a method of duplicating optical signals as they are, and a method of electrically duplicating traffic. Each method will be described later.

[0057] (Functional configuration of control device 50) The control device 50 includes a collection unit 51, a prediction unit 52, and a switching determination unit 53. The collection unit 51 collects load information related to the first communication device 30. In the following description, a case will be described in which the load information related to the first communication device 30 is traffic information. The collection unit 51 collects the traffic information from the first communication device 30.

[0058] The prediction unit 52 predicts a future load on the first communication device 30 based on the load information collected by the collection unit 51. The prediction unit 52 predicts a future traffic volume on the first communication device 30 based on, for example, traffic information collected by the collection unit 51. Note that any existing technology can be used to predict the future traffic volume.

[0059] The prediction unit 52 predicts the number of new connection terminals in the future in the first communication device 30, based on, for example, the number of new connection terminals collected by the collection unit 51. The prediction unit 52 predicts the future number of terminals for each QoS in the first communication device 30, based on, for example, the number of terminals for each QoS collected by the collection unit 51. The prediction unit 52 predicts the future CPU usage rate in the first communication device 30, based on, for example, the CPU usage rate collected by the collection unit 51.

[0060] The switching determination unit 53 determines in advance whether congestion will occur based on the future load on the first communication device 30 predicted by the prediction unit 52. The switching determination unit 53 determines in advance whether congestion will occur based on, for example, the future traffic volume on the first communication device 30 predicted by the prediction unit 52. If congestion is predicted to occur, the switching determination unit 53 determines to perform path switching for load balancing. Then, the switching determination unit 53 determines the second communication device 40 to be the switching destination.

[0061] The switching determination unit 53 may determine the second communication device 40 to switch to based on, for example, the available bandwidth information of the second communication device 40, the distance from the first communication device 30, or the CPU usage rate of the second communication device 40.

[0062] Delays in the optical path can be reduced by determining the second communication device 40, which is closer to the first communication device 30, as the switching destination. Delays in the hardware resources can be reduced by determining the second communication device 40, which has a lower CPU usage rate, as the switching destination.

[0063] After determining the second communication device 40 (for example, the second communication device 40-2) to be the switching destination, the switching determination unit 53 transmits a switching notification to the first communication device 30, the second communication device 40-1 as the switching source, and the second communication device 40-2 as the switching destination. The switching notification includes information for identifying the second communication device 40-2 as the switching destination.

[0064] (Functional configuration of subsequent device 60) The subsequent device 60 includes a selection unit 61 and an information processing unit 62. The selection unit 61 acquires traffic transmitted from each second communication device 40. The selection unit 61 outputs the acquired traffic to the information processing unit 62. Note that the selection unit 61 discards traffic that has already been acquired (for example, the same traffic) from the acquired traffic. The information processing unit 62 receives the traffic output from the selection unit 61 and processes it or transfers it to another network.

[0065] Next, a method for the duplicating unit 32 to duplicate traffic will be described with reference to FIGS. 5 and 6 . FIG. 5 is a diagram illustrating a first configuration example of the duplicating unit 32 in an embodiment. The duplicating unit 32 illustrated in FIG. 5 illustrates a configuration for electrically duplicating traffic. Therefore, when the traffic acquired by the information processing unit 31 is an optical signal, the information processing unit 31 converts the optical signal traffic (e.g., a main signal) into an electrical signal and outputs it to the duplicating unit 32. On the other hand, when the traffic acquired by the information processing unit 31 is an electrical signal, the information processing unit 31 outputs the acquired traffic to the duplicating unit 32.

[0066] The duplicating unit 32 is composed of a distributing unit 33, a first communication unit 34, and a second communication unit 35. The distributing unit 33 electrically duplicates input traffic by distributing (e.g., copying) the traffic. For example, the distributing unit 33 electrically duplicates the input traffic using port mirroring technology. The traffic duplicated by the distributing unit 33 is input to the first communication unit 34 and the second communication unit 35.

[0067] The first communication unit 34 transfers the traffic copied by the distribution unit 33 to the second communication device 40-1, which is the switching source, based on the header information. The first communication unit 34 is composed of a transfer control unit 341 and a first transfer unit 342. The transfer control unit 341 acquires the header information of the traffic copied by the distribution unit 33. The first transfer unit 342 determines a transfer destination based on the header information acquired by the transfer control unit 341, and transfers the traffic to the determined transfer destination.

[0068] The header information of the traffic includes information indicating the second communication device 40 that the first communication device 30 is currently using as the forwarding destination. Therefore, before the path switching is performed, the header information of the traffic includes information indicating the second communication device 40-1, which is the source of the path switching. In this case, the first forwarding unit 342 forwards the traffic copied by the distribution unit 33 to the second communication device 40-1.

[0069] On the other hand, after the path switching is completed, the header information of the traffic will include information indicating the second communication device 40-2, which is the switching destination. In this case, the first forwarding unit 342 forwards the traffic copied by the distribution unit 33 to the second communication device 40-2. In other words, the first communication unit 34 will stop transmitting traffic to the second communication device 40-1, which is the switching source, at the timing when the switching of the signal forwarding destination is completed.

[0070] The second communication unit 35 transfers the traffic copied by the distribution unit 33 to the second communication device 40-2, which is the switching destination, based on information indicating the switching destination included in the switching notification transmitted from the control device 50. The second communication unit 35 is composed of a transfer control unit 351 and a second transfer unit 352. The transfer control unit 351 acquires the information indicating the switching destination included in the switching notification transmitted from the control device 50. The second transfer unit 352 determines the transfer destination based on the information indicating the switching destination acquired by the transfer control unit 351, and transfers the traffic to the determined transfer destination.

[0071] For example, the information indicating the switching destination includes information indicating the second communication device 40-2, which is the switching destination. Therefore, the second forwarding unit 352 forwards the traffic copied by the distribution unit 33 to the second communication device 40-2, which is the switching destination.

[0072] On the other hand, after the path switching is completed, the control device 50 does not transmit a switching notification until the switching condition is satisfied again. Therefore, the transfer control unit 351 cannot obtain information indicating the switching destination. As a result, the second transfer unit 352 does not transfer the traffic duplicated by the distribution unit 33.

[0073] 6 is a diagram showing a second configuration example of the duplicating unit 32 in the embodiment. The duplicating unit 32 shown in FIG. 6 shows a configuration in which traffic is duplicated as an optical signal. Therefore, when the traffic acquired by the information processing unit 31 is an optical signal, the information processing unit 31 outputs the acquired traffic to the duplicating unit 32. Note that in the first communication device 30, a case will be considered in which a control signal is photoelectrically converted in the information processing unit 31 for the C-Plane, but is communicated as is in optical form for the U-Plane without electrical conversion.

[0074] The duplicating unit 32 is composed of an optical branching unit 36, a first communication unit 37, and a second communication unit 38. The optical branching unit 36 ​​duplicates traffic, which is an input optical signal, by branching it. The optical branching unit 36 ​​is, for example, an optical coupler. The traffic duplicated by the optical branching unit 36 ​​is input to the first communication unit 37 and the second communication unit 38.

[0075] The first communication unit 37 forwards the traffic to the second communication device 40-1, which is the source of switching, based on the header information of the traffic duplicated by the optical branching unit 36. The first communication unit 37 is composed of a forwarding control unit 371 and a first forwarding unit 372. The forwarding control unit 371 acquires the header information of the traffic duplicated by the optical branching unit 36. The first forwarding unit 372 determines a forwarding destination based on the header information acquired by the forwarding control unit 371, and forwards the traffic to the determined forwarding destination.

[0076] The header information of the traffic includes information indicating the second communication device 40 that the first communication device 30 is currently using as the forwarding destination. Therefore, before the path switching is performed, the header information of the traffic includes information indicating the second communication device 40-1, which is the source of the path switching. In this case, the first forwarding unit 372 forwards the traffic copied by the optical branching unit 36 ​​to the second communication device 40-1.

[0077] On the other hand, after the path switching is completed, the header information of the traffic will include information indicating the second communication device 40-2, which is the switching destination. In this case, the first forwarding unit 372 forwards the traffic copied by the distribution unit 33 to the second communication device 40-2. In other words, the first communication unit 37 will stop transmitting traffic to the second communication device 40-1, which is the switching source, at the timing when the switching of the signal forwarding destination is completed.

[0078] The second communication unit 38 converts the traffic copied by the optical branching unit 36 ​​to a wavelength of the switching destination based on information indicating the switching destination included in the switching notification transmitted from the control device 50, and forwards the traffic to the switching destination, the second communication device 40-2. The second communication unit 38 is composed of a forwarding control unit 381 and a second forwarding unit 382. The forwarding control unit 381 acquires the information indicating the switching destination included in the switching notification transmitted from the control device 50. The switching notification transmitted from the control device 50 includes, as information indicating the switching destination, information capable of identifying the second communication device 40-2, the switching destination, and information indicating the wavelength to be used by the second communication device 40-2. The second forwarding unit 382 determines a forwarding destination based on the information indicating the switching destination acquired by the forwarding control unit 381, and converts the traffic to the wavelength of the second communication device 40-2, the switching destination, and forwards the traffic.

[0079] On the other hand, after the path switching is completed, the control device 50 does not transmit a switching notification until the switching condition is satisfied again. Therefore, the forwarding control unit 381 cannot obtain information indicating the switching destination. As a result, the second forwarding unit 382 does not forward the traffic duplicated by the optical splitter 36.

[0080] 7 is a sequence diagram showing the flow of processing in the communication system 100 according to the embodiment. It is assumed that the first communication device 30 is transferring a signal via the second communication device 40-1 when the processing in FIG. 7 starts.

[0081] The information processing unit 31 of the first communication device 30 transmits traffic information to the control device 50 (step S101). Note that the information processing unit 31 may transmit the traffic information to the control device 50 periodically, in response to a request from the control device 50, or at a predetermined timing.

[0082] Furthermore, when the information processing unit 31 obtains traffic, it outputs the obtained traffic to the duplicating unit 32. Here, it is assumed that the obtained traffic is an optical signal, and that the configuration of the duplicating unit 32 is the configuration shown in FIG. 6. The duplicating unit 32 forwards the traffic output from the information processing unit 31 to a forwarding destination. Specifically, the traffic input to the duplicating unit 32 is first duplicated by the optical branching unit 36 ​​and input to the first communication unit 37 and the second communication unit 38. Next, the first communication unit 37 refers to header information of the input traffic. It is assumed that the header information of the traffic includes information indicating the second communication device 40-1. Then, the first communication unit 37 identifies a forwarding destination based on the header information of the traffic, and forwards the traffic to the identified forwarding destination, the second communication device 40-1 (step S102).

[0083] Note that the second communication unit 38 does not forward the input traffic because it has not received a switching notification from the control device 50. The second communication device 40-1 receives the traffic forwarded from the first communication device 30. The second communication device 40-1 forwards the received traffic to the subsequent device 60 (step S103). The subsequent device 60 receives the traffic forwarded from the second communication device 40-1 and processes it or forwards it to another network.

[0084] The collection unit 51 of the control device 50 collects traffic information transmitted from the first communication device 30 (step S104). The collection unit 51 outputs the collected traffic information to the prediction unit 52. The prediction unit 52 predicts future traffic volume in the first communication device 30 based on the traffic information output from the collection unit 51 (step S105). The prediction unit 52 outputs information indicating the predicted future traffic volume in the first communication device 30 to the switching determination unit 53. The switching determination unit 53 determines whether or not path switching is necessary based on the information indicating the future traffic volume in the first communication device 30 output from the prediction unit 52 (step S105).

[0085] For example, the switching determination unit 53 determines that route switching is necessary when congestion is predicted to occur based on the future traffic volume in the first communication device 30. On the other hand, the switching determination unit 53 determines that route switching is not necessary when congestion is not predicted to occur based on the future traffic volume in the first communication device 30. Here, the method of determining whether congestion will occur based on the future traffic volume may be the same as the method described above. Here, it is assumed that the switching determination unit 53 determines that route switching is necessary (step S106).

[0086] In this case, the switching determination unit 53 transmits a switching notification to the first communication device 30, the second communication device 40-1, which is the switching source, and the second communication device 40-2, which is the switching destination (step S107). The first communication device 30, the second communication device 40-1, and the second communication device 40-2 receive the switching notification transmitted from the control device 50. The first communication device 30, the second communication device 40-1, and the second communication device 40-2 execute a route switching process in response to the received switching notification (step S108). The route switching process is a process for switching the signal forwarding path. The specific flow of the route switching process will be described later.

[0087] The first communication device 30 starts redundant transfer in response to receiving the switching notification transmitted from the control device 50 (step S109). Here, redundant transfer means transferring traffic to both the second communication device 40-1, which is the switching source, and the second communication device 40-2, which is the switching destination. When the information processing unit 31 obtains traffic, it outputs the obtained traffic to the duplication unit 32. The duplication unit 32 forwards the traffic output from the information processing unit 31 to the transfer destination.

[0088] Specifically, first, the traffic input to the duplicating unit 32 is duplicated by the optical branching unit 36 ​​and input to the first communication unit 37 and the second communication unit 38. Next, the first communication unit 37 refers to the header information of the input traffic. Then, the first communication unit 37 identifies a forwarding destination based on the header information of the traffic, and forwards the traffic to the identified forwarding destination, the second communication device 40-1. Furthermore, since the second communication unit 38 has received a switching notification from the control device 50, it forwards the input traffic to the switching destination, the second communication device 40-2, based on information indicating the switching destination included in the switching notification (step S110).

[0089] Through the above processing, traffic is forwarded from the first communication device 30 to the second communication device 40-1 and the second communication device 40-2. The second communication device 40-1 receives the traffic forwarded from the first communication device 30. The second communication device 40-1 forwards the received traffic to the subsequent device 60 (step S111).

[0090] Furthermore, the second communication device 40-2 receives traffic forwarded from the first communication device 30. The second communication device 40-2 forwards the received traffic to the subsequent device 60 (step S112). The selection unit 61 of the subsequent device 60 receives the traffic forwarded from each of the second communication device 40-1 and the second communication device 40-2. If the received traffic is the same traffic, the selection unit 61 outputs the traffic that was acquired first to the information processing unit 62. The information processing unit 62 processes the traffic output from the selection unit 61 or forwards it to another network.

[0091] When the control device 50 receives a notification of completion of the path switching from the second communication device 40-1, which is the switching source, it transmits a switching completion instruction indicating that the path switching has been completed to the first communication device 30, the second communication device 40-1, and the second communication device 40-2 (step S113). In response to receiving the switching completion instruction transmitted from the control device 50, the first communication device 30 terminates the redundant transfer (step S114). Thereafter, when traffic is obtained, the first communication device 30 transfers the obtained traffic to the second communication device 40-2, which is the switching destination (step S115).

[0092] 8 is a sequence diagram showing the flow of the route switching process performed by the communication system 100 in the embodiment. In the route switching process shown in FIG. 8, the same processes as those in the route switching process shown in FIG. 3 are denoted by the same reference numerals as in FIG. 3, and the description thereof will be omitted. In FIG. 8, switching of the second communication device 40 is shown as an example. In the following description, the DU 30 in FIG. 8 corresponds to the first communication device 30 in FIG. 4, the Source 40-1 corresponds to the second communication device 40-1 in FIG. 2, and the Target CU 40-2 corresponds to the second communication device 40-2 in FIG. 2.

[0093] Assume that a trigger for path switching occurs in Source CU 40-1, to which DU 30 is connected (step S1). In this embodiment, the trigger is when the switching condition is satisfied, as described above. In this case, DU 30 starts redundant transfer of upstream traffic (step S21). Then, the processing from step S2 onwards is executed. After processing step S13, the U-Plane of Source CU 40-1 receives a BEARER CONTEXT REALEASE COMMAND transmitted from the C-Plane of Source CU 40-1. The U-Plane of Source CU 40-1 transmits a BEARER CONTEXT REALEASE COMPLETE to the C-Plane of Source CU 40-1 (step S14). Furthermore, the U-Plane of Source CU 40-1 transmits BEARER CONTEXT RELEASE COMPLETE to the control device 50 (step S22).

[0094] The control device 50 receives the BEARER CONTEXT RELEASE COMPLETE sent from the Source CU 40-1. The control device 50 recognizes that the path switching has been completed in response to the received BEARER CONTEXT RELEASE COMPLETE. The control device 50 then transmits a switching completion instruction to the Source CU 40-1, the Target CU 40-2, and the DU 30. The DU 30 receives the switching completion instruction sent from the control device 50 (step S23). In response to receiving the switching completion instruction, the DU 30 ends the redundant transfer. The DU 30 then transfers the upstream traffic to the Target CU 40-2 (step S24).

[0095] As described above, switching delays (in the case of electricity) and packet loss (in the case of optical) due to differences in switching timing between uplink and downlink can be eliminated by making the transfer path redundant. Furthermore, with this configuration, the processes of steps S9, S11, and S12 can be omitted, data transfer between devices becomes unnecessary, and the sequence (processing) required for switching can be reduced.

[0096] According to the communication system 100 configured as described above, the first communication device 30 has a duplication unit 32 that, when the switching condition is satisfied, copies the traffic (transfer data) to be forwarded and transfers the copied traffic to the second communication device 40-1, which is the source of the switching, and the second communication device 40-2, which is the destination of the switching.

[0097] In this way, from the time when the switching conditions are satisfied and route switching is initiated until route switching is completed, traffic is forwarded to both the second communication device 40-1, which is the source of switching, and the second communication device 40-2, which is the destination of switching. This makes it possible to suppress communication interruptions during switching. Therefore, packet loss can be reduced. Furthermore, switching delays can be suppressed even when a time difference occurs between switching downlink and uplink. Therefore, it is possible to suppress failures such as switching delays and packet loss during route switching.

[0098] Furthermore, in the communication system 100, the duplicating unit 32 of the first communication device 30 duplicates traffic electrically or as an optical signal. Therefore, the system can be applied regardless of whether the traffic is an electrical signal or an optical signal. This improves convenience.

[0099] (Variation 1) In the process of FIG. 8 , the second communication device 40-1, which is the switching source, notifies the control device 50 of a switching completion notification indicating the completion of path switching, and the first communication device 30 terminates the redundant transfer in response to receiving the switching completion instruction transmitted from the control device 50. The conditions under which the first communication device 30 terminates the redundant transfer are not limited to those described above. For example, the first communication device 30 may be configured to terminate the redundant transfer in response to receiving the switching completion notification transmitted from the second communication device 40-1, which is the switching source. In this configuration, the second communication device 40-1, which is the switching source, notifies the first communication device 30 of a switching completion notification in the process of step S22 shown in FIG. 8 . Then, the first communication device 30 may terminate the redundant transfer in response to receiving the switching completion notification transmitted from the second communication device 40-1, which is the switching source.

[0100] (Variation 2) In the above-described embodiment, the first communication device 30 (DU) starts redundant transfer upon receiving a switching notification from the control device 50. However, the timing at which the first communication device 30 (DU) starts redundant transfer is not limited to this. For example, the first communication device 30 may start redundant transfer due to a communication environment factor such as a handover between base stations. In a configuration like this, the first communication device 30 may start redundant transfer upon receiving a BEARER CONTEXT MODIFICATION REQUEST from the second communication device 40-1, which is the switching source. Then, the second communication device 40-1, which is the switching source, transmits BEARER CONTEXT REALEASE COMPLETE to the first communication device 30. The first communication device 30 ends redundant transfer upon receiving BEARER CONTEXT REALEASE COMPLETE.

[0101] (Variation 3) In the above-described embodiment, the case where the first communication device 30 is a DU (distributed unit) and the second communication device 40 is a CU (central unit) has been described as an example of a situation where path switching is performed based on upstream traffic, but the present invention can also be applied to other combinations. For example, the present invention can be applied to the following combinations. Combination 1: The first communication device 30 is a CU, and the second communication device 40 is a UPF. Combination 2: The first communication device 30 is a CU, and the second communication device 40 is a DU. Combination 3: The first communication device 30 is a UPF, and the second communication device 40 is a CU. Combination 4: The first communication device 30 is an OLT (Optical Line Terminal), and the second communication device 40 is an ONU (Optical Network Unit). Combination 5: The first communication device 30 is an ONU, and the second communication device 40 is an OLT.

[0102] The above-described combination 1 (the first communication device 30 is a CU and the second communication device 40 is a UPF) assumes a situation in which path switching is performed based on uplink traffic. In this configuration, the first communication device 30, which is a CU, may start redundant transfer in response to a Handover request. Upon starting redundant transfer, the first communication device 30 (CU) duplicates and forwards traffic to both the second communication device 40-1 (UPF), which is the source of switching, and the second communication device 40-2 (UPF), which is the destination of switching. The duplication method is as described above. Then, the first communication device 30 terminates redundant transfer in response to reception of a UE context release. Upon termination of redundant transfer, the first communication device 30 terminates forwarding of traffic to the second communication device 40-1 (UPF) and forwards traffic to the second communication device 40-2 (UPF).

[0103] The above-described combination 2 (the first communication device 30 is a CU and the second communication device 40 is a DU) assumes a situation in which path switching is performed based on downstream traffic. The configuration in this case is as shown in FIG. 9 . FIG. 9 is a diagram showing an example of the configuration of a communication system 100a in a modified example of the embodiment. The communication system 100a includes a first communication device 30, a plurality of second communication devices 40, a control device 50, and a subsequent device 60a. In FIG. 9 , the first communication device 30 is a CU, the second communication device 40 is a DU, and the subsequent device 60a is a UPF.

[0104] The communication system 100a may include at least a plurality of second communication devices 40. Hereinafter, it is assumed that the second communication device 40-1 is the source DU of switching, and the second communication device 40-2 is the destination DU of switching. The information processing unit 62 included in the subsequent device 60a transmits downstream traffic forwarded from the upper network to the first communication device 30. The information processing unit 31 of the first communication device 30 outputs the downstream traffic forwarded from the subsequent device 60a to the duplicating unit 32. Furthermore, the information processing unit 31 outputs load information to the control device 50.

[0105] In the configuration shown in FIG. 9 , the first communication device 30 starts redundant transfer upon receiving an RRC reconfiguration transmitted from the second communication device 40-1, which is the switching source. Upon starting redundant transfer, the first communication device 30 (CU) duplicates and forwards traffic to both the second communication device 40-1 (DU), which is the switching source, and the second communication device 40-2 (DU), which is the switching destination. The duplication method is as described above. Then, the first communication device 30 terminates redundant transfer upon receiving DL user data from a new route. Upon termination of redundant transfer, the first communication device 30 terminates forwarding of traffic to the second communication device 40-1 (DU) and forwards traffic to the second communication device 40-2 (DU).

[0106] The above-described combination 3 (the first communication device 30 is a UPF and the second communication device 40 is a CU) assumes a situation in which path switching is performed based on downstream traffic. In this configuration, the first communication device 30, which is a UPF, transmits traffic information as a REPORT to the control device 50, as shown in step S101 of FIG. 7. The control device 50 then performs prediction based on the traffic information. If the control device 50 determines that path switching is necessary, it transmits a switching notification to the first communication device 30, the second communication device 40-1, which is the source of switching, and the second communication device 40-2, which is the destination of switching. The first communication device 30 (UPF) may start redundant forwarding in response to the switching notification transmitted from the control device 50. Upon initiation of redundant forwarding, the first communication device 30 (UPF) duplicates and forwards traffic to both the second communication device 40-1 (CU), which is the source of switching, and the second communication device 40-2 (CU), which is the destination of switching. The duplication method is as described above. Then, the first communication device 30 ends the redundant transfer after transmitting the End marker. After that, the first communication device 30 ends the transfer of traffic to the second communication device 40-1 (CU) due to the end of the redundant transfer, and transfers traffic to the second communication device 40-2 (CU).

[0107] The above-described combination 4 (the first communication device 30 is an OLT and the second communication device 40 is an ONU) assumes a situation in which path switching is performed based on downstream traffic. In this configuration, the first communication device 30, which is the OLT, transmits traffic information (e.g., bandwidth allocation information and ONU location information) to the control device 50, as shown in step S101 of FIG. 7 . The bandwidth allocation information indicates the bandwidth allocated by the OLT to each ONU. The control device 50 then performs prediction based on the traffic information. If the control device 50 determines that path switching is necessary, it transmits a switching notification to the first communication device 30, the second communication device 40-1, which is the source of the path switching, and the second communication device 40-2, which is the destination of the path switching. The first communication device 30 (OLT) may initiate redundant transfer in response to the switching notification transmitted from the control device 50. When the redundant transfer is started, the first communication device 30 (OLT) copies and transfers traffic to both the second communication device 40-1 (ONU), which is the switching source, and the second communication device 40-2 (ONU), which is the switching destination. The method of copying is as described above. Then, the first communication device 30 ends the redundant transfer when it receives a switching completion instruction. When the redundant transfer is finished, the first communication device 30 ends the transfer of traffic to the second communication device 40-1 (ONU) and transfers traffic to the second communication device 40-2 (ONU).

[0108] The above-described combination 5 (the first communication device 30 is an ONU, and the second communication device 40 is an OLT) assumes a situation in which path switching is performed based on upstream traffic. The transmission request volume is determined from a REPORT sent from the ONU using the PON's DBA (Dynamic Bandwidth Allocation) function. Therefore, the control device 50 detects OLT congestion based on the REPORT information and uses this as a trigger to perform switching. The control device 50 then performs predictions based on the REPORT information. If the control device 50 determines that path switching is necessary, it transmits a switching notification to the first communication device 30, the second communication device 40-1 (the source of switching), and the second communication device 40-2 (the destination of switching). The first communication device 30, which is an ONU, may initiate redundant transfer upon receiving the switching notification sent from the control device 50. When the redundant transfer is started, the first communication device 30 (ONU) copies and transfers traffic to both the second communication device 40-1 (OLT), which is the switching source, and the second communication device 40-2 (OLT), which is the switching destination. The method of copying is as described above. Then, the first communication device 30 ends the redundant transfer when it receives a switching completion instruction. After that, when the redundant transfer is completed, the first communication device 30 ends the transfer of traffic to the second communication device 40-1 (OLT) and transfers traffic to the second communication device 40-2 (OLT).

[0109] Some of the functional units of the control device 50 in the above-described embodiment may be implemented by a computer. In this case, a program for implementing the functions may be recorded on a computer-readable recording medium, and the program may be read into a computer system and executed. Note that the term "computer system" here includes hardware such as an operating system (OS) and peripheral devices.

[0110] Furthermore, "computer-readable recording media" refers to portable media such as flexible disks, optical magnetic disks, ROMs (Read Only Memory), and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Furthermore, "computer-readable recording media" may also include devices that dynamically store programs for a short period of time, such as communication lines used when transmitting programs over networks like the Internet or communication lines like telephone lines, or devices that store programs for a fixed period of time, such as volatile memory within the computer systems that serve as servers or clients. Furthermore, the programs may be designed to realize some of the aforementioned functions, or may be capable of realizing the aforementioned functions in combination with programs already stored in the computer system, or may be realized using programmable logic devices such as FPGAs (Field Programmable Gate Arrays).

[0111] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention.

[0112] The present invention is applicable to technology.

[0113] 100...communication system, 30...first communication device, 40, 40-1 to 40-2...second communication device, 50...control device, 31...information processing unit, 32...duplicating unit, 33...distributing unit, 34, 37...first communication unit, 35, 38...second communication unit, 36...optical branching unit, 51...collecting unit, 52...predicting unit, 53...switching determination unit, 61...selecting unit, 62...information processing unit, 341, 351, 371, 381...transfer control unit, 342, 372...first transfer unit, 352, 382...second transfer unit

Claims

1. A communication device comprising a duplication unit that, when a switching condition for switching the destination of a signal is met, copies transfer data to be transferred and transfers the copied transfer data to a switching source communication device that is the source of the switching and a switching destination communication device that is the destination of the switching.

2. The communication device according to claim 1, wherein the duplicating unit electrically copies the transfer data.

3. The communication device according to claim 2, further comprising an information processing unit that converts the transfer data into electrical signal transfer data when the transfer data is an optical signal, and the duplicating unit electrically duplicates the electrical signal transfer data.

4. The communication device according to claim 1, wherein the duplicating unit copies the transfer data as is in optical form.

5. The communication device described in claim 4, wherein the duplication unit is composed of an optical branching unit that duplicates the transfer data, which is an optical signal, by branching it, a first communication unit that transfers the transfer data duplicated by the optical branching unit to the source communication device, and a second communication unit that converts the transfer data duplicated by the optical branching unit to a wavelength at the destination of switching and transfers it to the destination communication device.

6. A communication device according to any one of claims 1 to 5, wherein the duplicating unit stops sending the transfer data to the switching source communication device when switching of the transfer destination of the signal is completed.

7. A communication system comprising a first communication device, a plurality of second communication devices communicating with the first communication device, and a control device, wherein the plurality of second communication devices are a second communication device that is a switching source and a second communication device that is a switching destination, wherein the control device, when a switching condition for switching the transfer destination of a signal is satisfied, notifies the first communication device, the second communication device that is the switching source, and the second communication device that is the switching destination that the switching condition has been satisfied, and wherein the first communication device, at the timing when the notification is obtained from the control device, has a duplication unit that copies transfer data to be transferred and transfers the copied transfer data to the second communication device that is the switching source and the second communication device that is the switching destination.

8. A signal transfer method for duplicating transfer data to be transferred when a switching condition for the signal transfer destination is satisfied, and transferring the copied transfer data to a switching source communication device that is the switching source and a switching destination communication device that is the switching destination.

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