Control device, program, communication system, and control method

Abstract

This control device (20) is provided with: a communication unit (23) that communicates with a plurality of transfer devices; and a control unit (21) that sets a shared time slot for passing, as a flow of data communication performed along a path that passes through a port of at least one transfer device among the plurality of transfer devices, both a flow of a limited class including a specific class and a flow of one or more other classes, to the port through which the path passes via the communication unit (23), switches the shared time slot to a dedicated time slot for passing only the flow of the limited class via the communication unit (23) when a notification of the start of the flow of the specific class of the data communication is received from an external device, and returns the dedicated time slot to the shared time slot via the communication unit (23) when a notification of the end of the flow of the specific class of the data communication is received from the external device.

Description

Control device, program, communication system, and control method

[0001] The present disclosure relates to a control device, a program, a communication system, and a control method.

[0002] Patent Document 1 discloses a technique for allocating a bandwidth to a low-priority flow and changing the cycle of the high-priority flow when there is no high-priority flow.

[0003] Non-Patent Document 1 defines TAS. "TAS" is an abbreviation for time aware shaper. Non-Patent Document 2 discloses a technology that applies TAS to allocate time slots according to VLAN ID and priority. "VLAN" is an abbreviation for virtual local area network.

[0004] Japanese Patent Application Laid-Open No. 2020-136777

[0005] IEEE Computer Society, IEEE Std 802.1Qbv-2015, IEEE Standard for Local and metropolitan area networks -- Bridges and Bridged Networks - Amendment 25: Enhancements for Scheduled Traffic, 2016-03-18Yuhei Kawakami, et al., “Applying Time-aware Shaper Considering User Identifier to Service Provider Network”, IEEE 19th Annual Consumer Communications & Networking Conference, 2022

[0006] The technology disclosed in Patent Document 1 is not suitable for fixed-period communications, because it takes time to calculate time slots when the period is changed, which can result in the loss of high-priority frames.

[0007] By constructing a network with multiple nodes with TAS functionality, it is possible to achieve deterministic communication with little delay and jitter. In this case, it is necessary to assign time slots dedicated to deterministic communication to the output ports of all nodes that are passed through end-to-end.

[0008] The mechanism of TAS is shown in Figure 6. TAS performs priority control by determining the traffic to be transmitted according to a time-shared schedule. Specifically, TAS stores frames in FIFO queues for each VLAN-CoS or IP-ToS, and allows transmission from queues with open gates according to the GCL. "CoS" is an abbreviation for class of service. "IP" is an abbreviation for Internet Protocol. "ToS" is an abbreviation for type of service. "FIFO" is an abbreviation for first in, first out. "GCL" is an abbreviation for gate control list.

[0009] An example of a GCL is shown in Figure 7. TAS can control the overlapping of best-effort traffic and delay-guaranteed communication. In the example shown in Figure 7, four ST flows and one NST flow are multiplexed. "ST" is an abbreviation for scheduled traffic. "NST" is an abbreviation for non-scheduled traffic. ST flows correspond to delay-guaranteed communication. NST flows correspond to non-guaranteed communication, i.e., best-effort traffic. The GCL shown in Figure 7 specifies that STs with CoS "7" are permitted in timeslots 1 and 3, STs with CoS "5" in timeslot 2, STs with CoS "4" in timeslot 4, and NSTs with CoS "3" or less in timeslot 5. This GCL further specifies that the duration for which communication is permitted in each of timeslots 1 through 4 is 15 microseconds, and the duration for which communication is permitted in timeslot 5 is 100 microseconds.

[0010] To avoid collisions end-to-end, all nodes in the network must be time-synchronized and the timing of opening and closing the GCL gates at each node must be coordinated. The GCL is either centrally managed by a controller called a CNC, or managed individually at each node. "CNC" stands for centralized network configuration. Each node opens its gate taking propagation delays into account, preventing collisions with other communications and enabling communication without queuing delays. The transmitting terminal is also time-synchronized and periodically transmits frames in accordance with the GCL timing, enabling communication without queuing delays.

[0011] As described above, by having a frame for deterministic communication occupy a time slot that matches the time at which it passes through a node, transmission waits due to collisions with other frames are eliminated, and deterministic communication with little delay or jitter can be realized. However, time slots for deterministic communication are consumed even when no frames for deterministic communication are flowing.

[0012] The present disclosure has been made in view of the above circumstances, and aims to make effective use of a band for deterministic periodic communication when it is not in use.

[0013] A control device according to one embodiment is a control device that sets a plurality of time slots for each port of a plurality of transfer devices, and includes: a communication unit that communicates with the plurality of transfer devices; and a control unit that sets, via the communication unit, a shared time slot that allows both a flow of a limited class including a specific class and a flow of one or more other classes to pass as a data communication flow that is performed along a path that passes through a port of at least one of the plurality of transfer devices, to a port passed along the path; when notified by an external device of the start of a flow of the specific class of the data communication, switches, via the communication unit, the shared time slot to a dedicated time slot that allows only a flow of the limited class to pass; and when notified by the external device of the end of the flow of the specific class of the data communication, switches the dedicated time slot back to the shared time slot via the communication unit.

[0014] A control method according to one embodiment includes: a control device that sets multiple time slots for each port of multiple forwarding devices; setting a shared time slot, which allows both a flow of a limited class including a specific class and a flow of one or more other classes to pass along a path that passes through a port of at least one of the multiple forwarding devices, as a flow of data communication that is performed along the path; when the control device is notified by an external device of the start of a flow of the specific class of the data communication, switching the shared time slot to a dedicated time slot that allows only a flow of the limited class to pass; and when the control device is notified by the external device of the end of the flow of the specific class of the data communication, returning the dedicated time slot to the shared time slot.

[0015] According to the present disclosure, it is possible to effectively utilize a band for deterministic periodic communication when it is not in use.

[0016] FIG. 1 is a block diagram showing the configuration of a communication system according to one embodiment. FIG. 2 is a diagram showing the flow of frames according to a comparative example. FIG. 3 is a diagram showing the flow of frames according to one embodiment. FIG. 4 is a block diagram showing the configuration of a control device provided in a communication system. FIG. 5 is a diagram showing allocation of time slots according to a comparative example. FIG. 6 is a diagram showing allocation of time slots according to one embodiment. FIG. 7 is a flowchart showing the operation of a control device. FIG. 8 is a diagram showing the mechanism of TAS. FIG. 9 is a table showing an example of GCL.

[0017] An embodiment will be described below with reference to the drawings.

[0018] In each drawing, the same or corresponding parts are denoted by the same reference numerals. In the description of this embodiment, the description of the same or corresponding parts will be omitted or simplified as appropriate.

[0019] The configuration of a communication system 10 according to this embodiment will be described with reference to FIG.

[0020] The communication system 10 includes a control device 20 and a plurality of transfer devices such as transfer devices 31, 32, and 33. The control device 20 and each transfer device are connected by a monitoring and control network and can communicate with each other via the monitoring and control network. The plurality of transfer devices form a communication network and can transfer frames between any user terminals, such as between fixed-period communication terminals 41 and 42 or between general communication terminals 51 and 52, via the communication network.

[0021] The control device 20 is a computer that monitors and controls each forwarding device. Each forwarding device accommodates users and forwards frames to a port designated for each destination user terminal. The number of forwarding devices is three in this embodiment, but it may be two, or four or more. Each user terminal is, for example, a mobile terminal such as a smartphone or tablet, a general-purpose terminal such as a PC, or a dedicated terminal for a specific purpose. "PC" is an abbreviation for personal computer. Each user terminal can be either the start point or the end point of a flow.

[0022] In this embodiment, the transfer device 31 and the fixed-period communication terminal 41 are connected. The transfer device 31 and the general communication terminal 51 are connected. The transfer device 33 and the fixed-period communication terminal 42 are connected. The transfer device 33 and the general communication terminal 52 are connected. The transfer device 31 and the transfer device 33 are connected. The transfer device 32 and the transfer device 33 are connected. Therefore, a communication frame sent from the fixed-period communication terminal 41 to the fixed-period communication terminal 42 passes through the transfer device 31, the transfer device 32, and the transfer device 33 in this order before reaching the fixed-period communication terminal 42. A communication frame sent from the fixed-period communication terminal 42 to the fixed-period communication terminal 41 passes through the transfer device 33, the transfer device 32, and the transfer device 31 in this order before reaching the fixed-period communication terminal 41. The path of the communication frame between the general communication terminals 51 and 52 is similar to the path of the communication frame between the fixed-period communication terminals 41 and 42, so a description thereof will be omitted.

[0023] An outline of this embodiment will be described with reference to FIG.

[0024] In a communication system 10 in which frames for deterministic communication and frames for general communication coexist, a predetermined time slot for deterministic communication is allocated exclusively for the deterministic communication of a user during a usage period designated by the user of the deterministic communication, and the time slot is also allocated for general communication during other periods. Therefore, according to this embodiment, the band for deterministic communication can be effectively utilized when not in use.

[0025] In this embodiment, the control device 20 calculates time slots for fixed-period communication and sets them to each of the transfer devices 31, 32, and 33 on the route between the fixed-period communication terminals 41 and 42. The control device 20 also sets time slots for general communication. The time slots for fixed-period communication are set so that they can also be used for general communication. In other words, the time slots for fixed-period communication can also be used for communication between the general communication terminals 51 and 52.

[0026] When the control device 20 is notified of the start of definite-period communication via the web system 60 or one of the transfer devices, the control device 20 controls the transfer devices 31, 32, and 33 to change the settings to exclusively use the time slots for definite-period communication. The general communication terminals 51 and 52 are no longer able to use the time slots for definite-period communication, and the definite-period communication terminals 41 and 42 communicate using the exclusively used time slots. When the control device 20 is notified of the end of definite-period communication via the web system 60 or one of the transfer devices, the control device 20 controls the transfer devices 31, 32, and 33 to change the settings to share the time slots for definite-period communication. With this change, the general communication terminals 51 and 52 also return to a state where they can communicate using the time slots for definite-period communication. The control device 20 may calculate a usage fee from the accumulated value of the usage time of definite-period communication, and notify and bill the user via the web system 60.

[0027] The flow of frames within each transfer device will be described with reference to Figures 2A and 2B. Figure 2A shows the flow of frames according to a comparative example. Figure 2B shows the flow of frames according to an example of this embodiment.

[0028] In both examples, assume that frames for deterministic communication to be transferred in the third and fifth time slots are circulating, while general communication frames continue to flow. In the comparative example shown in FIG. 2A , general communication frames cannot be transmitted in time slots reserved for deterministic communication. Specifically, because the first and seventh time slots are also exclusively used, general communication frames cannot be transmitted in the first and seventh time slots even if there are no frames for deterministic communication to be transmitted in those time slots. On the other hand, in the embodiment shown in FIG. 2B , by specifying the timing at which deterministic communication distribution starts and ends, general communication frames can be transmitted in time slots reserved for deterministic communication. As a result, frames can be transmitted using all time slots. Specifically, because the timing at which deterministic communication distribution starts is not specified until the third time slot, general communication frames can be transmitted in the first time slot. After the third time slot is specified as the timing at which deterministic communication distribution starts, the fifth time slot is specified as the timing at which distribution ends, so general communication frames can also be transmitted in the seventh time slot. For example, if the fifth time slot is designated as the timing for ending distribution, and a frame for deterministic communication and a frame for general communication arrive at the same time in the seventh time slot, it is desirable that the frame for deterministic communication be transferred with priority over the frame for general communication. However, if the arrival of the frame for deterministic communication is delayed, the frame for general communication may be transferred first.

[0029] The configuration of the control device 20 according to this embodiment will be described with reference to FIG.

[0030] The control device 20 includes a control unit 21 , a storage unit 22 , and a communication unit 23 .

[0031] The control unit 21 includes at least one processor, at least one programmable circuit, at least one dedicated circuit, or any combination thereof. The processor is a general-purpose processor such as a CPU or GPU, or a dedicated processor specialized for specific processing. "CPU" is an abbreviation for central processing unit. "GPU" is an abbreviation for graphics processing unit. An example of the programmable circuit is an FPGA. "FPGA" is an abbreviation for field-programmable gate array. An example of the dedicated circuit is an ASIC. "ASIC" is an abbreviation for application specific integrated circuit. The control unit 21 controls each part of the control unit 20 and executes processing related to the operation of the control unit 20.

[0032] The storage unit 22 includes at least one semiconductor memory, at least one magnetic memory, at least one optical memory, or any combination thereof. The semiconductor memory is, for example, a RAM, a ROM, or a flash memory. "RAM" is an abbreviation for random access memory. "ROM" is an abbreviation for read only memory. RAM is, for example, an SRAM or a DRAM. "SRAM" is an abbreviation for static random access memory. "DRAM" is an abbreviation for dynamic random access memory. ROM is, for example, an EEPROM. "EEPROM" is an abbreviation for electrically erasable programmable read only memory. Flash memory is, for example, an SSD. "SSD" is an abbreviation for solid-state drive. Magnetic memory is, for example, an HDD. "HDD" is an abbreviation for hard disk drive. The storage unit 22 functions, for example, as a main storage device, an auxiliary storage device, or a cache memory. The storage unit 22 stores information used in the operation of the control device 20 and information obtained by the operation of the control device 20 .

[0033] The communication unit 23 includes at least one communication module. The communication module is, for example, a module that complies with a LAN communication standard such as Ethernet (registered trademark). The communication unit 23 communicates with each transfer device. The communication unit 23 may also communicate with the web system 60. The communication unit 23 receives information used in the operation of the control device 20 and transmits information obtained by the operation of the control device 20.

[0034] The functions of the control device 20 are realized by executing a program according to this embodiment on a processor serving as the control unit 21. That is, the functions of the control device 20 are realized by software. The program causes a computer to execute the operations of the control device 20, thereby causing the computer to function as the control device 20. That is, the computer functions as the control device 20 by executing the operations of the control device 20 in accordance with the program.

[0035] The program can be stored on a non-transitory computer-readable medium. Examples of the non-transitory computer-readable medium include flash memory, magnetic recording devices, optical disks, magneto-optical recording media, and ROMs. The program can be distributed by selling, transferring, or lending portable media such as SD cards, DVDs, or CD-ROMs that store the program. "SD" is an abbreviation for Secure Digital. "DVD" is an abbreviation for digital versatile disc. "CD-ROM" is an abbreviation for compact disc read only memory. The program can also be distributed by storing it in the storage of a server and transferring it from the server to another computer. The program can also be provided as a program product.

[0036] A computer temporarily stores a program stored on a portable medium or transferred from a server in its main storage device. The computer then reads the program stored in the main storage device with its processor and executes processing in accordance with the read program. The computer may also read the program directly from the portable medium and execute processing in accordance with the program. The computer may also execute processing in accordance with the received program each time a program is transferred from the server to the computer. Processing may also be executed using a so-called ASP-type service that realizes functions simply by issuing execution instructions and obtaining results, without transferring the program from the server to the computer. "ASP" is an abbreviation for application service provider. A program is information used for processing by a computer and includes something equivalent to a program. For example, data that is not a direct instruction to a computer but has properties that define computer processing falls under the category of "something equivalent to a program."

[0037] Some or all of the functions of the control device 20 may be implemented by a programmable circuit or a dedicated circuit as the control unit 21. In other words, some or all of the functions of the control device 20 may be implemented by hardware.

[0038] In this embodiment, the control unit 21 has a time slot calculation function 24, a time slot setting function 25, and a deterministic period communication management function 26. The time slot calculation function 24 is a function that calculates in advance the time slots to be allocated to deterministic period communication. The time slot setting function 25 is a function that allocates time slots to deterministic period communication and general communication, and allocates the time slots allocated to deterministic period communication so that they can be shared with general communication. The deterministic period communication management function 26 is a function that switches the time slots for deterministic period communication to exclusive use when deterministic period communication begins to be used, and switches the time slots to shared use when deterministic period communication ends.

[0039] The control unit 21 may further include a usage fee calculation function 27. The usage fee calculation function 27 is a function that accumulates the usage time of the fixed-cycle communication and calculates the usage fee.

[0040] The storage unit 22 stores information about the time slots assigned by the time slot setting function 25 as time slot information 11. The time slot information 11 is referenced by the fixed cycle communication management function 26.

[0041] The communication unit 23 transmits information about the time slot when the time slot is assigned by the time slot setting function 25 and when the time slot is switched by the fixed cycle communication management function 26 to each transfer device as setting information 12.

[0042] Each transfer device holds both a table that sets the allocation of time slots for transferring frames for deterministic periodic communication, and a table that sets the allocation of time slots that are shared between deterministic periodic communication and other communications. Upon receiving setting information 12, each transfer device generates, updates, or switches tables according to the received setting information 12.

[0043] 4A and 4B, the allocation of time slots in the table held by the transfer device 31 will be described. Fig. 4A shows the allocation of time slots according to a comparative example. Fig. 4B shows the allocation of time slots according to an example of this embodiment.

[0044] In both examples, the transfer device 31 includes an input port 34, a frame distribution unit 35, and an output port 36. It is assumed that definite-period communications D1, D2, and D3 are performed between definite-period communication terminals 41 and 42, and general communications BE such as best-effort communications are performed between general communication terminals 51 and 52. The definite-period communications D1, D2, and D3 may be identified based on priority alone, or may be identified based on VLAN ID and priority, similar to the technology disclosed in Non-Patent Document 2.

[0045] In the comparative example shown in FIG. 4A , the control unit 21 of the control device 20 calculates a time slot based on a combination of period and bandwidth that matches the time at which frames of the deterministic period communications D1, D2, and D3 pass through the transfer device 31. As the number of transfer devices on the communication path or the number of flows of deterministic period communications with different periods or bandwidths increases, calculating the time slots to be dedicated takes time. Therefore, the control unit 21 of the control device 20 calculates the time slots to be assigned in advance and sets them in the transfer device 31. In the table 70 held by the transfer device 31, the time slots calculated according to the flows of deterministic period communications D1, D2, and D3 are set as those for the deterministic period communications D1, D2, and D3, and the other time slots are set as those for general communications BE. Specifically, the first, fifth, ninth, and so on are set as those for the deterministic period communications D1. The second, seventh, and so on are set as those for the deterministic period communications D2. The sixth and so on are set as those for the deterministic period communications D3. The third, fourth, eighth, and so on time slots are set for general communication BE. The transfer device 31 refers to the identification information of each frame received from the input port 34, distributes each frame to the assigned time slot in the frame distribution unit 35, and sends out the frames carried by each time slot from the output port 36.

[0046] In this example, frames for deterministic periodic communication exclusively use time slots that match the times at which they pass through the transfer device 31, eliminating transmission waits due to collisions with other frames and enabling deterministic periodic communication with little delay and jitter. However, time slots for deterministic periodic communication are consumed even when frames for deterministic periodic communication are not flowing.

[0047] In the embodiment shown in FIG. 4B , similar to the comparative example, the control unit 21 of the control device 20 calculates the time slots to be assigned in advance and sets them in the transfer device 31. However, the time slots calculated to match the flows of the definite-period communications D1, D2, and D3 are not dedicated to the definite-period communications D1, D2, and D3, but are set as shared with the general communication BE. The time slots calculated to match the flows of the definite-period communications D1, D2, and D3 are also set in the first table 71 held by the transfer device 31. The other time slots are set for the general communication BE, similar to the table 70 of the comparative example. Specifically, the first, fifth, ninth, and so on are set as shared by the definite-period communication D1 and the general communication BE. The second, seventh, and so on are set as shared by the definite-period communication D2 and the general communication BE. The sixth, and so on, are set as shared by the definite-period communication D3 and the general communication BE. The third, fourth, eighth, and so on time slots are set as those for general communication BE. In a second table 72 that the transfer device 31 holds separately from the first table 71, similar to the table 70 of the comparative example, time slots calculated in accordance with the flows of the definite-cycle communications D1, D2, and D3 are set as those dedicated to the definite-cycle communications D1, D2, and D3.

[0048] When the control unit 21 of the control device 20 is notified by the user of the start and end timings of frame distribution for the definite-period communications D1, D2, and D3, the control unit 21 records these timings in the storage unit 22. The user may specify the start and end dates and times of distribution in advance to reserve the switchover, or may notify the user immediately before the start and end of distribution to request an immediate switchover. The control unit 21 of the control device 20 switches the first table 71 of the transfer device 31 to the second table 72 in accordance with the start of the definite-period communications D1, D2, and D3, and switches back to the first table 71 in accordance with the end of the definite-period communications D1. For example, the control unit 21 of the control device 20 switches a part of the first table 71 to the second table 72 in accordance with the start of the definite-period communication D1, thereby switching the time slot shared by the definite-period communication D1 and the general communication BE to a time slot dedicated to the definite-period communication D1. The control unit 21 of the control device 20 restores the part of the first table 71 that has been switched to the second table 72 in accordance with the timing at which the fixed period communication D1 ends, thereby returning the dedicated time slot for the fixed period communication D1 to a time slot shared by the fixed period communication D1 and the general communication BE.

[0049] According to this example, when switching between dedicated and shared time slots, recalculation of the time slot is not required, and switching can be performed in a short time without affecting frame forwarding. As in the comparative example, low-latency and low-jitter deterministic period communication is realized, and communication resources can be used for other general communication during periods when frames for deterministic period communication are not flowing.

[0050] The control unit 21 of the control device 20 may accumulate the time when the time slot is not exclusive, i.e., is shared, and reflect this in the user's usage fee for fixed-period communication. In such an example, the user can reduce the usage fee for fixed-period communication by notifying the timing of the start and end of the fixed-period communication.

[0051] The allocation of time slots in the tables held by the transfer devices 32 and 33 is similar to the allocation of time slots in the table held by the transfer device 31, and therefore a description thereof will be omitted.

[0052] The operation of the control device 20 according to this embodiment will be described with reference to Fig. 5. The operation described below corresponds to a control method according to this embodiment. That is, the control method according to this embodiment includes at least steps S1 to S4 shown in Fig. 5.

[0053] Prior to S1, the control unit 21 sets multiple time slots for each port of the multiple forwarding devices. Specifically, the control unit 21 sets, via the communication unit 23, a common time slot for a port along a path via which both a flow of a limited class including a specific class and a flow of one or more other classes pass as a data communication flow performed along a path via a port of at least one of the multiple forwarding devices. The "limited class" may include only a specific class such as CoS "7," or may further include classes other than the specific class, such as CoS "6." The "one or more other classes" may be any class, or may be limited to several classes, such as CoS "3" or lower. In this embodiment, the control unit 21 sets, as a common time slot, a time slot for passing both a flow of a limited class between a specific combination of terminals and a flow of one or more other classes between any combination of terminals. When the ST flow with CoS "7" between fixed-cycle communication terminals 41 and 42 is the flow of fixed-cycle communication D1, and the NST flow with CoS "3" or less between any terminals is the flow of general communication BE, in the example shown in Figure 4B, the control unit 21 sets the first, fifth, ninth, ... time slots to the output port 36 of the transfer device 31 as time slots shared by the fixed-cycle communication D1 and general communication BE. When the control unit 21 has completed setting the time slots, it begins waiting.

[0054] When the control unit 21 receives notification from an external device in S1 of the start of a data communication flow of a specific class, the control unit 21 switches, in S2, via the communication unit 23, the shared time slot to a dedicated time slot that allows only flows of a limited class to pass. In this embodiment, at least one transfer device holds both a first table 71 containing settings for shared time slots and a second table 72 containing settings for dedicated time slots, as tables containing settings for multiple time slots. Therefore, the control unit 21 switches between the first table 71 and the second table 72 via the communication unit 23, thereby switching between the shared time slot and the dedicated time slot. In the example shown in FIG. 4B , when the control unit 21 receives notification from a user via the web system 60 of the start of a definite-period communication D1 flow, the control unit 21 switches the shared time slot for the definite-period communication D1 and the general communication BE to a dedicated time slot for the definite-period communication D1 by causing the transfer device 31 to switch a part of the first table 71 to the second table 72.

[0055] When the control unit 21 is notified in S3 by an external device of the end of a data communication flow of a specific class, in S4 the control unit 21 returns the dedicated time slot to a shared time slot via the communication unit 23. In the embodiment shown in Fig. 4B, when the control unit 21 is notified by the user via the web system 60 of the end of the flow of determinate period communication D1, the control unit 21 causes the transfer device 31 to restore the part of the first table 71 that has been switched to the second table 72, thereby returning the dedicated time slot for determinate period communication D1 to a shared time slot for determinate period communication D1 and general communication BE.

[0056] Steps S1 to S4 are repeatedly executed. According to this embodiment, by executing steps S1 to S4, it is possible to effectively utilize the band for deterministic period communication when it is not in use.

[0057] The control unit 21 may count the time from when the shared time slot is switched to a dedicated time slot to when the dedicated time slot is switched back to a shared time slot, and calculate a fee based on the counted time. In the embodiment shown in Figure 4B, the control unit 21 may count the time from when the shared time slot for the determined-period communication D1 and the general communication BE is switched to a dedicated time slot for the determined-period communication D1 to when the dedicated time slot is switched back to the shared time slot, and calculate a fee based on the counted time as a usage fee for the determined-period communication D1. The control unit 21 may bill the user for the calculated fee via the communication unit 23 and the web system 60.

[0058] The following additional notes are provided regarding the above-described embodiments.

[0059] (Supplementary Item 1) A control device that sets a plurality of time slots for each port of a plurality of transfer devices, comprising: a communication unit that communicates with the plurality of transfer devices; and a control unit that sets, via the communication unit, a shared time slot that passes both a flow of a limited class including a specific class and flows of one or more other classes as a flow of data communication that is performed along a path that passes through a port of at least one of the plurality of transfer devices, to a port passed through the path; when notified by an external device of the start of a flow of the specific class of the data communication, switches, via the communication unit, the shared time slot to a dedicated time slot that passes only flows of the limited class; and when notified by the external device of the end of the flow of the specific class of the data communication, returns the dedicated time slot to the shared time slot via the communication unit. (Supplementary Item 2) The control device according to Supplementary Item 1, wherein the control unit counts the time from when the shared time slot is switched to the dedicated time slot to when the dedicated time slot is returned to the shared time slot; and calculates a fee according to the counted time. (Supplementary Item 3) The control device according to Supplementary Item 1 or Supplementary Item 2, wherein the control unit sets, as the shared time slot, a time slot that passes both a flow of the limited class between a specific combination of terminals and a flow of the other one or more classes between any combination of terminals. (Supplementary Item 4) The control device according to any one of Supplementary Item 1 to Supplementary Item 3, wherein the limited class includes only the specific class. (Supplementary Item 5) A program that causes a computer to function as the control device according to any one of Supplementary Item 1 to Supplementary Item 4. (Supplementary Item 6) A communication system comprising: the control device according to any one of Supplementary Item 1 to Supplementary Item 4; and the plurality of transfer devices.(Supplementary Item 7) The at least one transfer device holds both a first table containing the settings of the shared time slots and a second table containing the settings of the dedicated time slots as tables containing the settings of the multiple time slots, and the control unit of the control device switches between the shared time slots and the dedicated time slots by causing the at least one transfer device to switch between the first table and the second table via the communication unit. This is the communication system described in Supplementary Item 6. (Supplementary Item 8) A control method comprising: a control device that sets multiple time slots for each port of multiple transfer devices, setting a shared time slot for a port passed through on the path, the shared time slot allowing both a flow of a limited class including a specific class and a flow of one or more other classes to pass as a flow of data communication performed along the path passing through a port of at least one of the multiple transfer devices; when the control device is notified by an external device of the start of a flow of the specific class of the data communication, switching the shared time slot to a dedicated time slot allowing only a flow of the limited class to pass; and when the control device is notified by the external device of the end of the flow of the specific class of the data communication, switching the dedicated time slot back to the shared time slot.

[0060] The present disclosure is not limited to the above-described embodiments. For example, two or more blocks shown in the block diagram may be integrated, or one block may be divided. Two or more steps shown in the flowchart may be executed in parallel or in a different order, instead of being executed in chronological order as described, depending on the processing capabilities of the device executing each step, or as needed. Other modifications are possible within the scope of the present disclosure.

[0061] REFERENCE SIGNS LIST 10 Communication system 11 Time slot information 12 Setting information 20 Control device 21 Control unit 22 Storage unit 23 Communication unit 24 Time slot calculation function 25 Time slot setting function 26 Fixed cycle communication management function 27 Usage fee calculation function 31, 32, 33 Transfer device 34 Input port 35 Frame distribution unit 36 ​​Output port 41, 42 Fixed cycle communication terminal 51, 52 General communication terminal 60 Web system 70 Table 71 First table 72 Second table

Claims

1. A control device that sets multiple time slots for each port of multiple transfer devices, comprising: a communication unit that communicates with the multiple transfer devices; and a control unit that sets, via the communication unit, a shared time slot that allows both a limited class flow including a specific class and one or more other class flows to pass as a data communication flow that is performed along a path that passes through a port of at least one of the multiple transfer devices, to a port passed through the path; when notified by an external device of the start of the specific class flow of the data communication, switches via the communication unit the shared time slot to a dedicated time slot that allows only the limited class flow to pass; and when notified by the external device of the end of the specific class flow of the data communication, switches via the communication unit the dedicated time slot back to the shared time slot.

2. The control device according to claim 1, wherein the control unit counts the time from when the shared time slot is switched to the dedicated time slot until when the dedicated time slot is switched back to the shared time slot, and calculates a fee according to the counted time.

3. The control device according to claim 1, wherein the control unit sets the shared time slot as a time slot that passes both the limited class of flows between a specific combination of terminals and the other one or more classes of flows between any combination of terminals.

4. The control device of claim 1, wherein the limited class includes only the specific class.

5. A program that causes a computer to function as the control device according to any one of claims 1 to 4.

6. A communication system comprising: a control device according to any one of claims 1 to 4; and a plurality of transfer devices.

7. The communication system described in claim 6, wherein the at least one transfer device holds both a first table containing the settings of the common time slots and a second table containing the settings of the dedicated time slots as tables containing the settings of the plurality of time slots, and the control unit of the control device switches between the common time slots and the dedicated time slots by causing the at least one transfer device to switch between the first table and the second table via the communication unit.

8. A control method comprising: a control device that sets multiple time slots for each port of multiple transfer devices; setting a shared time slot, which allows both a limited class of flow including a specific class and one or more other class of flows to pass as a data communication flow along a path that passes through a port of at least one of the multiple transfer devices; when the control device is notified by an external device of the start of the specific class of the data communication flow, switching the shared time slot to a dedicated time slot that allows only the limited class of flows to pass; and when the control device is notified by the external device of the end of the specific class of the data communication flow, returning the dedicated time slot to the shared time slot.

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