Control device, program, communication system, and control method

Abstract

A control device (20) comprises a control unit (21) that: sets, via a communication unit (23), a shared time slot which allows the passage of both a flow of a limited class including a specific class and a flow of at least one other class as flows of data communication that is carried out along a route passing through a port of at least one transfer device among a plurality of transfer devices, for the port through which the route passes; switches, via the communication unit (23), the shared time slot to a dedicated time slot which allows only the flow of the limited class in the data communication between a specific combination of bases, in accordance with the start of the flow of the specific class between the specific combination of bases; and returns, via the communication unit (23), the dedicated time slot to the shared time slot in accordance with the end of the flow of the specific class in the data communication between the specific combination of bases.

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] 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.

[0003] 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

[0004] 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.

[0005] The mechanism of TAS is shown in Figure 8. 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.

[0006] An example of a GCL is shown in Figure 9. TAS can control best-effort traffic and delay-guaranteed communication by superimposing them together. In the example shown in Figure 9, 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 9 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 are permitted 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.

[0007] 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.

[0008] As described above, in TAS, a controller designs an end-to-end route for each user (i.e., for each flow) requiring deterministic communication, calculates the time slots for each node along the route, and assigns dedicated time slots for each flow to each node in the form of a GCL. The node identifies the flow of each incoming frame, places each frame in the designated time slot for the identified flow, and transmits each frame according to the time slot. By occupying a time slot that matches the time at which a frame for deterministic communication passes through a node, transmission waits due to collisions with other frames are eliminated, enabling deterministic communication with low latency and jitter. However, because each flow occupies a dedicated time slot, a huge amount of bandwidth is required to accommodate a large number of flows. Furthermore, because it takes time to calculate the end-to-end time slot allocation for each user, it is difficult to immediately allocate time slots when needed.

[0009] In view of these circumstances, the objective of the present disclosure is to instantly allocate end-to-end time slots for each user when needed, without reserving a huge amount of bandwidth, even when accommodating a large number of flows.

[0010] 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 through the path; switches, via the communication unit, the shared time slot to a dedicated time slot that allows only a flow of the limited class between the specific combination of bases to pass, in accordance with the start of the data communication flow of the specific class between the specific combination of bases; and switches, via the communication unit, the dedicated time slot back to the shared time slot in accordance with the end of the data communication flow of the specific class between the specific combination of bases.

[0011] A control method according to one embodiment includes: a control device that sets multiple time slots for each port of multiple transfer devices; a control device that sets a common time slot for a port passed through on a route that passes through a port of at least one of the multiple transfer devices, the common 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 data communication flow that is performed along the route that passes through the port of the transfer device; the control device switching the common time slot to a dedicated time slot that allows only a flow of the limited class between the specific combination of bases to pass, in accordance with the start of the flow of the specific class between the specific combination of bases in the data communication; and the control device returning the dedicated time slot to the common time slot in accordance with the end of the flow of the specific class between the specific combination of bases in the data communication.

[0012] According to the present disclosure, even when accommodating a large number of flows, end-to-end time slots for each user can be instantly allocated when needed without reserving a huge amount of bandwidth.

[0013] 1 is a block diagram showing the configuration of a communication system according to an embodiment; FIG. 2 is a diagram showing bandwidth reservation according to a comparative example; FIG. 3 is a diagram showing bandwidth reservation by a communication system; FIG. 4 is a block diagram showing the configuration of a control device provided in a communication system; FIG. 5 is a diagram showing an example of time slot allocation for section Y; FIG. 6 is a flowchart showing the operation of the control device; FIG. 7 is a block diagram showing a modified example of the configuration of a communication system; FIG. 8 is a diagram showing an example of time slot allocation for section X; FIG. 9 is a diagram showing an example of time slot allocation for section Y; FIG. 10 is a diagram showing an example of time slot switching for section X; FIG. 11 is a diagram showing the mechanism of TAS; and FIG. 12 is a table showing an example of GCL.

[0014] An embodiment will be described below with reference to the drawings.

[0015] 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.

[0016] The configuration of a communication system 10 according to this embodiment will be described with reference to FIG.

[0017] 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 of bases such as bases A, B, C, and D via the communication network.

[0018] 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.

[0019] In this embodiment, the transfer device 31 is connected to the fixed-period communication terminal 41 and the general communication terminal 51 at the base A. The transfer device 32 is connected to the fixed-period communication terminal 42 and the general communication terminal 52 at the base B. The transfer device 33 is connected to the fixed-period communication terminal 43 and the general communication terminal 53 at the base C, and the fixed-period communication terminal 44 at the base D. The transfer device 31 is connected to the transfer device 32. The transfer device 32 is connected to the transfer device 33.

[0020] A communication frame sent from the fixed-period communication terminal 41 at point A addressed to the fixed-period communication terminal 42 at point B passes through transfer device 31 and transfer device 32 in this order before reaching the fixed-period communication terminal 42 at point B. A communication frame sent from the fixed-period communication terminal 42 at point B addressed to the fixed-period communication terminal 41 at point A passes through transfer device 32 and transfer device 31 in this order before reaching the fixed-period communication terminal 41 at point A. The path of the communication frame between the general communication terminal 51 at point A and the general communication terminal 52 at point B is similar to the path of the communication frame between the fixed-period communication terminal 41 at point A and the fixed-period communication terminal 42 at point B, and therefore will not be described here.

[0021] A communication frame sent from the fixed-period communication terminal 41 at point A addressed to the fixed-period communication terminal 43 at point C passes through transfer device 31, transfer device 32, and transfer device 33 in this order before reaching the fixed-period communication terminal 43 at point C. A communication frame sent from the fixed-period communication terminal 43 at point C addressed to the fixed-period communication terminal 41 at point A passes through transfer device 33, transfer device 32, and transfer device 31 in this order before reaching the fixed-period communication terminal 41 at point A. The path of the communication frame between the fixed-period communication terminal 41 at point A and the fixed-period communication terminal 44 at point D, and the path of the communication frame between the general communication terminal 51 at point A and the general communication terminal 53 at point C are similar to the path of the communication frame between the fixed-period communication terminal 41 at point A and the fixed-period communication terminal 43 at point C, and therefore will not be described here.

[0022] A communication frame sent from the fixed-period communication terminal 42 at point B addressed to the fixed-period communication terminal 43 at point C passes through the transfer device 32 and the transfer device 33 in that order before reaching the fixed-period communication terminal 43 at point C. A communication frame sent from the fixed-period communication terminal 43 at point C addressed to the fixed-period communication terminal 42 at point B passes through the transfer device 33 and the transfer device 32 in that order before reaching the fixed-period communication terminal 42 at point B. The path of the communication frame between the fixed-period communication terminal 42 at point B and the fixed-period communication terminal 44 at point D, and the path of the communication frame between the general communication terminal 52 at point B and the general communication terminal 53 at point C are similar to the path of the communication frame between the fixed-period communication terminal 42 at point B and the fixed-period communication terminal 43 at point C, and therefore will not be described here.

[0023] In this embodiment, combinations of periods and bandwidths available for deterministic periodic communication are patterned. Specifically, the time slots allocated in the section X between the transfer devices 31 and 32 are limited to time slots for the first pattern P1 of deterministic periodic communication and time slots for general communication BE, such as best-effort communication. The time slots allocated in the section Y between the transfer devices 32 and 33 are limited to time slots for the first pattern P1 of deterministic periodic communication, time slots for the second pattern P2 of deterministic periodic communication, and time slots for general communication BE. The time slots for the first pattern P1 are shared by multiple users performing deterministic periodic communication and are exclusively used by that user only when that user needs to perform deterministic periodic communication. The time slots for the second pattern P2 are always exclusively used by a user for performing deterministic periodic communication. The time slots for general communication BE are time slots not allocated to either the first pattern P1 or the second pattern P2. For example, the first pattern P1 is a pattern in which one frame is assigned at a 500-millisecond period and the frame length is 1,000 bytes. The second pattern P2 is a pattern in which one frame is formed at a period of 200 milliseconds and the frame length is 500 bytes.

[0024] An outline of this embodiment will be described with reference to FIG.

[0025] In a communication system 10 in which multiple deterministic period communication flows circulate in multiple intervals, time slots allocated to the deterministic period communication are predetermined for each interval and for whether or not they can be shared. A shared time slot is allocated to multiple flows that share a time slot. When an exclusive period is specified for one of the multiple flows that share a time slot, that time slot is allocated to that flow as an exclusive time slot during the exclusive period. Therefore, according to this embodiment, even when accommodating a large number of flows, end-to-end time slots for each user can be allocated instantly when needed without having to reserve a huge amount of bandwidth.

[0026] In this embodiment, the control device 20 calculates time slots for each section of the communication path and for each pattern. For each flow of deterministic communication to be accommodated, the control device 20 pre-sets time slots for sections on the communication path that match the pattern. The pre-set time slots are set so that multiple deterministic communication flows can share them as long as the capacity limit is not exceeded. The control device 20 stores the time slots assigned to each flow, and when a signal is given that a flow with a certain deterministic period is flowing, the control device 20 switches the setting of the time slot through which the flow is flowing to one that is exclusively used by the flow. When a signal is given that the flow is ending, the control device 20 changes the setting back from exclusive to shared. The start and end signals may be issued from the user terminal by user operation, or may be issued from the operation system by operation of a telecommunications carrier operator.

[0027] As shown in Fig. 2A, if bandwidth is accumulated for each path end-to-end for bases A, B, C, and D, it would be necessary to secure a huge amount of communication resources. In this embodiment, as shown in Fig. 2B, by setting time slots for each section and for each pattern, it becomes possible to provide a deterministic period communication service to a large number of bases without having to secure a huge amount of communication resources.

[0028] The configuration of the control device 20 according to this embodiment will be described with reference to FIG.

[0029] The control device 20 includes a control unit 21 , a storage unit 22 , and a communication unit 23 .

[0030] 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.

[0031] 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 .

[0032] The communication unit 23 includes at least one communication module. The communication module is, for example, a module compatible with a LAN communication standard such as Ethernet (registered trademark). The communication unit 23 communicates with each transfer device. The communication unit 23 may communicate with a user terminal operated by a user, an operation system operated by an operator, or another system that relays information from the user terminal or the operation system. 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.

[0033] 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.

[0034] 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.

[0035] 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."

[0036] 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.

[0037] In this embodiment, the control unit 21 has a time slot calculation function 24 and a time slot setting function 25. The time slot calculation function 24 is a function that calculates in advance the time slot to be assigned to definite-period communication for each section and for each pattern. The time slot setting function 25 is a function that assigns a time slot to multiple flows whose patterns and sections overlap so that the time slot can be shared. The time slot setting function 25 also includes a function that, when a certain definite-period communication flow starts communication, switches the time slot of the section through which the flow passes to exclusive use by that flow, and, when the communication ends, switches the time slot to shared among multiple flows.

[0038] The storage unit 22 stores information about the time slots assigned by the time slot setting function 25 as time slot information 11 .

[0039] When a time slot is assigned by the time slot setting function 25 and when a time slot is switched by the time slot setting function 25, information about the time slot is transmitted from the communication unit 23 to each transfer device as setting information 12.

[0040] 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.

[0041] An example of time slot allocation in a table held by the transfer device 32 will be described with reference to FIG.

[0042] The transfer device 32 includes an input port 34, a frame distribution unit 35, and an output port 36. In this example, it is assumed that deterministic periodic communications of a first pattern P1 are performed between bases A and C, between bases A and D, and between bases B and C, that deterministic periodic communications of a second pattern P2 are performed between bases B and D, and that general communications BE are performed between any bases. The deterministic periodic communications are identified according to a VLAN ID and a priority, similar to the technology disclosed in Non-Patent Document 2. That is, each flow of deterministic periodic communications is identified by a VLAN ID as the flow between the bases.

[0043] The control unit 21 of the control device 20 uses a time slot calculation function 24 to calculate time slots for each transfer device that are suitable for the deterministic period communication pattern and designs a time slot allocation table. The control unit 21 of the control device 20 uses a time slot setting function 25 to set the calculated time slot allocation table for each transfer device in advance. In the first table 71 held by the transfer device 32, time slots shared by the first pattern P1 of deterministic period communication and the general communication BE, time slots for the second pattern P2 of deterministic period communication, and time slots for the general communication BE are set. Specifically, the first, fifth, ninth, etc. time slots are set as those shared by the first pattern P1 of deterministic period communication and the general communication BE. The second, seventh, etc. time slots are set for the second pattern P2 of deterministic period communication. The third, fourth, sixth, eighth, etc. time slots are set for the general communication BE. In a second table 72 that the transfer device 32 maintains separately from the first table 71, time slots are set that are dedicated to fixed-period communication between individual combinations of bases, such as between bases A and C. "O" in the diagram is an abbreviation for open. The transfer device 32 references the identification information of each frame received from the input port 34, and allocates each frame to a time slot that matches the time slot allocation table in the frame allocation unit 35, and sends out the frames carried by each time slot from the output port 36.

[0044] The control unit 21 of the control device 20 uses the time slot setting function 25 to instruct switching between exclusive and shared time slots at the start and end of definite-period communication. When a signal is received to start using definite-period communication for another flow for an already exclusive time slot, the control unit 21 of the control device 20 uses the time slot setting function 25 to respond that exclusive use is not permitted. For example, if the transfer device 32 receives an instruction from the control device 20 to switch the first time slot from shared to exclusive between sites A and C, the transfer device 32 switches part of the first table 71 to the second table 72, thereby switching the first time slot to a time slot exclusive to definite-period communication between sites A and C. If the transfer device 32 then receives an instruction from the control device 20 to return the first time slot to shared, the transfer device 32 restores the part of the first table 71 that was switched to the second table 72, thereby returning the first time slot to a shared time slot. The cases of exclusive use between bases A and D and exclusive use between bases B and C are similar to the case of exclusive use between bases A and C, and therefore description thereof will be omitted.

[0045] As described above, in this example, time slots for deterministic periodic communication are patterned. The time slots designed for each section include time slots shared by multiple deterministic periodic communication flows. When a signal is given that a deterministic periodic communication flow is about to start distribution, the corresponding time slot on the route is dedicated. When a signal is given that distribution is about to end, the time slot is switched to a shared time slot. When a signal is given from another flow that a dedicated time slot is about to start distribution, the user is notified that the time slot is unavailable. This example makes it possible to effectively utilize the bandwidth for deterministic periodic communication when it is not in use.

[0046] 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.

[0047] 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 flows of a limited class including a specific class and flows of one or more other classes pass as data communication flows 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 flows of a limited class with a common period and bandwidth between at least two combinations of bases and flows of one or more other classes between any combination of bases. The "specific combination" described below refers to any one of "at least two combinations." When the ST flows with CoS "7" between points A and C, between points A and D, and between points B and C are defined as flows of the first pattern P1 of determinate period communication, and the NST flows with CoS "3" or less between any terminals are defined as flows of general communication BE, in the example shown in Figure 4, the control unit 21 sets the first, fifth, ninth, ... time slots to the output port 36 of the transfer device 32 as time slots shared by the first pattern P1 of determinate period communication and the general communication BE. When the control unit 21 has completed setting the time slots, it begins waiting.

[0048] 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 between a specific combination of bases, in S2, the control unit 21 switches, via the communication unit 23, the shared time slot to a dedicated time slot that allows only flows of a limited class between the specific combination of bases to pass. That is, in accordance with the start of a data communication flow of a specific class between the specific combination of bases, the control unit 21 switches, via the communication unit 23, the shared time slot to a dedicated time slot that allows only flows of a limited class between the specific combination of bases to pass. In this embodiment, at least one transfer device holds both a first table 71 that includes settings for shared time slots and a second table 72 that includes settings for dedicated time slots, as tables that include 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 Figure 4, when the control unit 21 is notified by a user or operator about the start of the flow of the first pattern P1 of the fixed period communication between bases A and C, it causes the transfer device 32 to switch part of the first table 71 to the second table 72, thereby switching the shared time slot for the first pattern P1 of the fixed period communication and general communication BE to a time slot dedicated to the fixed period communication between bases A and C.

[0049] In this embodiment, the control unit 21 prohibits the start of a limited class of data communication flows whose period and bandwidth are common to flows that pass through the dedicated time slot between at least two combinations of bases other than a specific combination, during the period from when the shared time slot is switched to a dedicated time slot until the dedicated time slot is switched back to a shared time slot. In the example shown in Figure 4, when the control unit 21 is notified by a user or operator of the start of a flow of the first pattern P1 of determinate-period communication between bases A and D or between bases B and C during the period from when the shared time slot between the first pattern P1 of determinate-period communication and the general communication BE is switched to a time slot dedicated to determinate-period communication between bases A and C until the time slot is switched back to the shared time slot, the control unit 21 notifies the user or operator via the communication unit 23 that the flow is unavailable.

[0050] 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 between a specific combination of bases, the control unit 21 returns the dedicated time slot to a shared time slot via the communication unit 23 in S4. That is, in accordance with the end of the data communication flow of a specific class between a specific combination of bases, the control unit 21 returns the dedicated time slot to a shared time slot via the communication unit 23. In the example shown in Fig. 4, when the control unit 21 is notified by a user or operator of the end of the flow of first pattern P1 of determinate period communication between bases A and C, the control unit 21 causes the transfer device 32 to restore the portion of the first table 71 that was switched to the second table 72, thereby returning the time slot dedicated to the determinate period communication between bases A and C to a shared time slot for the first pattern P1 of determinate period communication and general communication BE.

[0051] Steps S1 to S4 are repeatedly executed. According to this embodiment, by executing steps S1 to S4, even when a large number of flows are accommodated, end-to-end time slots for each user can be immediately assigned when necessary without reserving a huge amount of bandwidth.

[0052] 6, a modified configuration of the communication system 10 will be described. This modified configuration may be applied to cases where a carrier provides low-latency, low-jitter deterministic communication over a wide area network, such as haptic communication or remote robot control.

[0053] In this modification, transfer device 31 is connected to terminal A, which is a terminal at base A, and terminal B, which is a terminal at base B. Transfer device 32 is connected to terminal C, which is a terminal at base C. Transfer device 33 is connected to terminal D, which is a terminal at base D.

[0054] A communication frame sent from terminal A to terminal C passes through transfer device 31 and transfer device 32 in this order before reaching terminal C. A communication frame sent from terminal C to terminal A passes through transfer device 32 and transfer device 31 in this order before reaching terminal A. The path of a communication frame between terminal B and terminal C is the same as the path of a communication frame between terminal A and terminal B, so a description thereof will be omitted.

[0055] A communication frame sent from terminal A to terminal D passes through transfer device 31, transfer device 32, and transfer device 33 in this order before reaching terminal D. A communication frame sent from terminal D to terminal A passes through transfer device 33, transfer device 32, and transfer device 31 in this order before reaching terminal A. The path of a communication frame between terminal B and terminal D is the same as the path of a communication frame between terminal A and terminal D, so a description thereof will be omitted.

[0056] A communication frame sent from terminal C to terminal D passes through transfer device 32 and transfer device 33 in this order before reaching terminal D. A communication frame sent from terminal D to terminal C passes through transfer device 33 and transfer device 32 in this order before reaching terminal C.

[0057] In this modification, the time slots allocated in the section X between the transfer devices 31 and 32 are limited to the time slots for the first pattern P1 of deterministic periodic communication, the time slots for the second pattern P2 of deterministic periodic communication, and the time slots for general communication BE such as best-effort communication. The time slots allocated in the section Y between the transfer devices 32 and 33 are limited to the time slots for the first pattern P1 of deterministic periodic communication and the time slots for general communication BE. The time slots for the first pattern P1 are shared by multiple users performing deterministic periodic communication and are exclusively used by that user only when that user needs to perform deterministic periodic communication. The time slots for the second pattern P2 are always exclusively used by a user to perform deterministic periodic communication. The time slots for general communication BE are time slots that are not allocated to either the first pattern P1 or the second pattern P2.

[0058] An example of time slot allocation in the tables held by the transfer devices 31 and 32 will be described with reference to FIGS. 7A to 7D.

[0059] In this example, periodic communication of the first pattern P1 is performed between terminals A and D, between terminals B and D, and between terminals C and D, periodic communication of the second pattern P2 is performed between terminals B and C, and general communication BE is performed between any terminals.

[0060] 7A, the first table 73 held by the transfer device 31 has time slots set as shared time slots for the first pattern P1 of deterministic periodic communication and the general communication BE, time slots for the second pattern P2 of deterministic periodic communication, and time slots for the general communication BE. Specifically, the first, fifth, ninth, and so on are set as time slots shared by the first pattern P1 of deterministic periodic communication and the general communication BE. The second, seventh, and so on are set as time slots for the second pattern P2 of deterministic periodic communication. The third, fourth, sixth, eighth, and so on are set as time slots for the general communication BE.

[0061] 7B , in the first table 74 held by the transfer device 32, time slots shared by the first pattern P1 of deterministic period communication and the general communication BE, and time slots for the general communication BE are set. Specifically, the first, fifth, ninth, and so on are set as time slots shared by the first pattern P1 of deterministic period communication and the general communication BE. The second, third, fourth, sixth, seventh, eighth, and so on are set as time slots for the general communication BE. In a second table 75 held by the transfer device 32 separately from the first table 74, time slots dedicated to deterministic period communication between individual combinations of bases, such as between bases C and D, are set.

[0062] As described above, in this example, terminals A, B, and C share the time slots for the first pattern P1 in order to perform definite-period communication with terminal D at the same period and frequency band. Terminals B and C exclusively use other time slots in order to constantly perform definite-period communication according to the second pattern P2. The control device 20 calculates in advance, for each section, i.e., for each section X and Y, the time slots to be assigned to terminal D when a connection request for definite-period communication is received from any of terminals A, B, and C, and sets a time slot allocation table in each transfer device.

[0063] For example, when the control device 20 receives a signal to start deterministic periodic communication between bases C and D, it switches a portion of the first table 74 held by the transfer device 32 to the second table 75, thereby switching the time slots for the first pattern P1 of the deterministic periodic communication in section Y to be used exclusively for the flow between bases C and D. During this time, the control device 20 dedicates the time slots for the first pattern P1 of the deterministic periodic communication in section Y exclusively for communication between bases C and D, and returns a response indicating that the time slots cannot be exclusively used if a signal to start another deterministic periodic communication is received. When the control device 20 receives a signal to end the deterministic periodic communication between bases C and D, it restores the portion of the first table 74 that was switched to the second table 75, thereby switching the time slots for the first pattern P1 of the deterministic periodic communication in section Y to be shared with other flows.

[0064] For example, when the control device 20 receives a signal to start definite-period communication between bases A and D, it switches a portion of the first tables 73 and 74 held by the transfer devices 31 and 32 to the second tables, as shown in Figures 7C and 7D, thereby switching the time slots for the first pattern P1 of the definite-period communication in each of the sections X and Y to be used to the exclusive use of the flow between bases A and D. During this time, the control device 20 dedicates the time slots for the first pattern P1 of the definite-period communication in each of the sections X and Y to communication between bases A and D only, and returns a response indicating that the time slots cannot be exclusive when a signal to start another definite-period communication is received. When the control device 20 receives a signal to end the definite-period communication between bases A and D, it restores the portions of the first tables 73 and 74 that were switched to the second tables, thereby switching the time slots for the first pattern P1 of the definite-period communication in each of the sections X and Y to be shared with other flows. 7C conveniently shows a state in which a portion of the first table 73 held by the transfer device 31 has been switched to the second table as table 76, and the portion of the first table 73 that has been switched to the second table as table 77. FIG. 7D conveniently shows a state in which a portion of the first table 74 held by the transfer device 32 has been switched to the second table as table 78, and the portion of the first table 74 that has been switched to the second table as table 79.

[0065] According to this example, it is possible to communicate frames of general communication BE using the time slots allocated for the first pattern P1.

[0066] The following additional notes are provided regarding the above-described embodiments.

[0067] (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 common time slot that passes both a flow of a limited class including a specific class and a flow of one or more other classes as a flow of data communication 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; switching, via the communication unit, the common time slot to a dedicated time slot that passes only a flow of the limited class between the specific combination of bases in accordance with a start of a flow of the specific class between the specific combination of bases in the data communication; and switching, via the communication unit, the dedicated time slot back to the common time slot in accordance with an end of the flow of the specific class between the specific combination of bases in the data communication. (Supplementary Item 2) The control device according to Supplementary Item 1, wherein the control unit sets, as the common time slot, a time slot that passes flows of the limited class between at least two combinations of bases, having a common period and bandwidth, and the specific combination is any one of the at least two combinations. (Supplementary Item 3) The control device according to Supplementary Item 2, wherein the control unit prohibits the initiation of a flow of the limited class having a period and bandwidth common to a flow passing through the dedicated time slot between bases of a combination other than the specific combination among the at least two combinations of data communication, during the period 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. (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 a route that passes through a port of at least one of the multiple transfer devices, 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 that occurs along the route that passes through the port of at least one transfer device among the multiple transfer devices; the control device switching the shared time slot to a dedicated time slot that allows only a flow of the limited class between the specific combination of bases to pass, in accordance with the start of a flow of the specific class between the specific combination of bases in the data communication; and the control device returning the dedicated time slot to the shared time slot in accordance with the end of the flow of the specific class between the specific combination of bases in the data communication.

[0068] 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.

[0069] 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 31, 32, 33 Transfer device 34 Input port 35 Frame distribution unit 36 ​​Output port 41, 42, 43, 44 Fixed cycle communication terminal 51, 52, 53 General communication terminal 71, 73, 74 First table 72, 75 Second table 76, 77, 78, 79 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 common 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 occurs along a route that passes through a port of at least one of the multiple transfer devices, to a port passed through the route; switches, via the communication unit, the common time slot to a dedicated time slot that allows only a flow of the limited class between the specific combination of bases to pass, in accordance with the start of the data communication flow of the specific class between the specific combination of bases; and switches, via the communication unit, the dedicated time slot back to the common time slot in accordance with the end of the data communication flow of the specific class between the specific combination of bases.

2. The control device described in claim 1, wherein the control unit sets the shared time slot as a time slot that passes flows of the limited class with a common period and bandwidth between at least two combinations of bases, and the specific combination is any one of the at least two combinations.

3. The control device according to claim 2, wherein the control unit prohibits the initiation of a flow of the limited class having a period and bandwidth common to the flow passing through the dedicated time slot between bases of a combination other than the specific combination among the at least two combinations of data communication during the period from when the shared time slot is switched to the dedicated time slot until when the dedicated time slot is returned to the shared time slot.

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 common time slot for a port passed through on a route that passes through a port of at least one of the multiple transfer devices, the common time slot allowing 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 that occurs along the route that passes through the port of at least one of the multiple transfer devices; the control device switching the common time slot to a dedicated time slot that allows only a limited class of flow to pass between the specific combination of bases in accordance with the start of the specific class of flow in the data communication between the specific combination of bases; and the control device returning the dedicated time slot to the common time slot in accordance with the end of the specific class of flow in the data communication between the specific combination of bases.

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