Scheduling method and control device

Abstract

A control device (10) according to the present disclosure comprises a control unit (12). On the basis of a transmission schedule of priority traffic in each of a plurality of switches, the control unit (12) determines whether any fragmentation is existent or not at the exit port of one switch. When having determined that a fragmentation is existent, the control unit determines whether any shiftable traffic is existent or not among the priority traffics that are to be transmitted at the exit port of the one switch. When having determined that a shiftable traffic is existent, the control unit determines whether the fragmentations are to be reduced or not as the whole network (2) by the change of the transmission schedule in each of the multiple switches in association with the change of the transmission timing of the shiftable traffic. When having determined that the fragmentations are to be reduced as the whole network (2), the control unit changes the transmission schedule in each of the multiple switches.

Description

Technical Field

[0001] The present disclosure relates to a scheduling method and a control device.

Background Art

[0002] A communication system that introduces Time Aware Shaper (TAS), which is time-deterministic communication, and transfers scheduled traffic of multiple users (hereinafter referred to as "priority traffic") on a layer 2 network with low latency and low jitter has been studied. In TAS, scheduling is performed so that priority traffic is transferred without colliding with each other in the network (see Non-Patent Document 1).

[0003] FIG. 11 is a diagram showing an example of a communication system 1a in which TAS is introduced. In the example shown in FIG. 11, four switches SW1 to SW4 are provided on the network 2. The switch SW3 is connected to each of the switches SW1, SW2, and SW4. The priority traffic of each of Talker #1 to Talker #4 is transferred to Listener #5 or Listener #6 via the switches SW1 to SW4.

[0004] In TAS, the transmission timing for transmitting priority traffic from the egress port of each of the switches SW1 to SW4 is scheduled. FIG. 12 is a diagram showing an example of the transmission schedule of the priority traffic of each of Talker #1 to Talker #4 in the communication system 1a shown in FIG. 11.

[0005] In the example shown in Figure 12, priority traffic for Talker #1 and Talker #2 is scheduled to be sent in that order to exit port a from switch SW1 to switch SW3, priority traffic for Talker #3, Talker #4, and Talker #2 is scheduled to be sent in that order to exit port b from switch SW2 to switch SW3, and priority traffic for Talker #1, Talker #3, Talker #4, and Talker #2 is scheduled to be sent in that order to exit port c from switch SW3 to switch SW4. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] IEEE Standard for Local and Metropolitan Area Networks- Bridges and Bridged Networks IEEE std 802.1Q-2018 [Overview of the project] [Problems that the invention aims to solve]

[0007] In a communication system like the one shown in Figure 11, not only priority traffic but also traffic consisting of frames transmitted on a best-effort basis (hereinafter referred to as "BE traffic") is transmitted. Specifically, as shown in Figure 12, BE traffic is transmitted during the remaining time within a predetermined time (cycle time) when priority traffic is not being transmitted.

[0008] Network communications change constantly due to user registration and deactivation. In the example shown in Figure 12, for example, if the communication of Talker #4 is deactivated, a gap will appear in the time slot where Talker #4's priority traffic transmission was scheduled, as shown in Figure 13A. When a gap appears in the priority traffic transmission schedule, if the time domain for transmitting multiple priority traffics within the cycle time remains constant, there is a problem in that the time available for BE traffic transmission does not change even though there are periods when priority traffic is not transmitted, and the efficiency of data transfer cannot be improved. In other words, as shown in Figure 13B, if a gap appears in the priority traffic transmission schedule, the time available for BE traffic transmission can be increased by reducing the transmission interval of priority traffic, thereby improving the efficiency of data transfer.

[0009] Therefore, in order to improve the forwarding efficiency of BE traffic, it is conceivable to review and change the transmission schedule for each port of all existing priority traffic after an update, such as when users are added or removed. However, in a network provided by a telecommunications carrier, changing the transmission schedule for all priority traffic every time users are added or removed would require significant computational resources. Furthermore, if the computation time required to review the transmission schedule of priority traffic is longer than the update cycle of priority traffic, the optimization to improve the forwarding efficiency of BE traffic may not be performed properly.

[0010] In light of the problems described above, the purpose of this disclosure is to provide a scheduling method and control device that can improve the efficiency of data transfer while suppressing cost increases. [Means for solving the problem]

[0011] To solve the above problems, the scheduling method according to the present disclosure is a scheduling method for the transmission schedule of priority traffic in a network that forwards priority traffic consisting of a series of frames transmitted with a maximum delay guaranteed, where the transmission timing of the switches is reserved by the switches, the scheduling method includes: acquiring the transmission schedule of the priority traffic at each of the multiple switches; determining, based on the acquired transmission schedule, whether or not there is fragmentation at the exit port of one switch where there is an interval of a predetermined value or more between the transmission timing of one priority traffic and the transmission timing of the next priority traffic; if it is determined that fragmentation exists, determining whether or not there is movable traffic among the priority traffic transmitted at the exit port of one switch where the interval can be reduced by performing defragmentation which changes the transmission timing; if it is determined that movable traffic exists, determining whether or not the fragmentation will decrease in the entire network due to the change in the transmission schedule at each of the multiple switches due to the change in the transmission timing of the movable traffic; and if it is determined that the fragmentation will decrease in the entire network, changing the transmission schedule at each of the multiple switches.

[0012] To solve the above problems, the control device according to the present disclosure is a control device for controlling the transmission schedule of priority traffic in a network that forwards priority traffic consisting of a series of frames transmitted with a maximum delay guaranteed, where the transmission timing of the switches is reserved by the switches, and the transmission schedule of the priority traffic is guaranteed, and the control device comprises a control unit, which determines, based on the transmission schedule of the priority traffic in each of the multiple switches, whether or not there is fragmentation at the exit port of one switch where there is an interval of a predetermined value or more between the transmission timing of one priority traffic and the transmission timing of the next priority traffic, and if it is determined that the fragmentation exists, it determines whether or not there is movable traffic among the priority traffic transmitted at the exit port of one switch where the interval can be reduced by performing defragmentation which changes the transmission timing, and if it is determined that there is movable traffic, it determines whether or not the fragmentation will decrease in the network as a whole due to the change in the transmission schedule in each of the multiple switches due to the change in the transmission timing of the movable traffic, and if it is determined that the fragmentation will decrease in the network as a whole, it changes the transmission schedule in each of the multiple switches. [Effects of the Invention]

[0013] The scheduling method and control device described herein make it possible to improve the efficiency of data transfer while suppressing cost increases. [Brief explanation of the drawing]

[0014] [Figure 1] This figure shows an example configuration of a communication system to which a control device according to one embodiment of this disclosure is applied. [Figure 2] This figure shows an example of the configuration of the control device shown in Figure 1. [Figure 3] This figure shows an example of priority traffic forwarding by multiple switches. [Figure 4]It is a flowchart showing an example of the operation of the control unit shown in FIG. 2. [Figure 5] It is a diagram showing an example of the scheduling matrix created by the control unit shown in FIG. 2. [Figure 6] It is a diagram showing an example of the change of the transmission schedule by the control unit shown in FIG. 2. [Figure 7] It is a diagram showing another example of the transfer of priority traffic by a plurality of switches. [Figure 8] It is a diagram showing an example of a collision of priority traffic. [Figure 9] It is a diagram showing another example of the change of the transmission schedule by the control unit shown in FIG. 2. [Figure 10] It is a diagram showing an example of the hardware configuration of the control device according to the present disclosure. [Figure 11] It is a diagram showing a configuration example of a conventional communication system. [Figure 12] It is a diagram showing an example of the transmission schedule of priority traffic in the communication system shown in FIG. 11. [Figure 13A] It is a diagram showing an example of the transmission schedule of priority traffic when the communication of a user is canceled in the communication system shown in FIG. 11. [Figure 13B] It is a diagram showing an example of the change of the transmission schedule shown in FIG. 13A.

Mode for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0016] Figure 1 shows an example configuration of a communication system 1 to which a control device 10 according to one embodiment of the present disclosure is applied. As shown in Figure 1, the communication system 1 comprises a plurality of switches SW (switches SW1 to SW4) and a control device 10, which are provided on a network 2. Data is transferred from the source to the destination by the plurality of switches SW1 to SW4. In this embodiment, the transmission timing of switches SW1 to SW4 is reserved, and priority traffic consisting of a series of frames transmitted with a guaranteed maximum delay and traffic consisting of a series of frames transmitted on a best-effort basis (BE traffic) are transmitted. As explained with reference to Figure 13, within a predetermined time (cycle time), BE traffic is transmitted during the remaining time when priority traffic is not transmitted.

[0017] The control device 10 according to this embodiment is connected to each of the switches SW1 to SW4 and controls the transmission schedule of priority traffic by each of the switches SW1 to SW4. Figure 1 shows an example in which the control device 10 is provided separately from the switches SW1 to SW4, but it is not limited to this. In the communication system 1 shown in Figure 1, the switches SW1 to SW4 may each have a function to be controlled autonomously. In this case, the control device 10 may be mounted on, for example, one or more switches SW. Hereafter, the control device 10 will be described as being provided separately from the switches SW1 to SW4, as shown in Figure 1.

[0018] Figure 2 shows an example of the configuration of the control device 10 according to this embodiment.

[0019] As shown in Figure 2, the control device 10 according to this embodiment comprises a communication unit 11 and a control unit 12.

[0020] The communication unit 11 can communicate with each of the multiple switches SW1 to SW4 on the network 2. For example, the communication unit 11 can send and receive priority traffic transmission schedules with each of the switches SW1 to SW4.

[0021] The control unit 12 obtains the transmission schedule for priority traffic on each of the multiple switches SW1 to SW4 via the communication unit 11. Based on the obtained transmission schedule, the control unit 12 determines whether or not it is necessary to change the transmission schedule for priority traffic. If the control unit 12 determines that it is necessary to change the transmission schedule for priority traffic, it changes the transmission schedule for priority traffic on each of the multiple switches SW1 to SW4 and transmits the changed transmission schedule to each of the multiple switches SW1 to SW4 via the communication unit 11.

[0022] As shown in Figure 2, the control unit 12 comprises a matrix generation unit 121, a fragmentation determination unit 122, a movable traffic determination unit 123, an increase / decrease measurement unit 124, and a schedule change unit 125. The operation of each part of the control unit 12 will be described in more detail below. In the following, as shown in Figure 3, priority traffic F1 is transmitted from the exit port P1 of switch SW1 to switch SW2, priority traffic F1 and priority traffic F2 are transmitted from the exit port P2 of switch SW2 to switch SW4, priority traffic F3 is transmitted from the exit port P3 of switch SW3 to switch SW4, and priority traffic F1, priority traffic F2, and priority traffic F3 are transmitted from the exit port P4 of switch SW4.

[0023] Figure 4 is a flowchart showing an example of the operation of the control unit 12, and is a diagram for explaining the scheduling method by the control device 10 according to this embodiment.

[0024] The matrix generation unit 121 obtains the transmission schedules for priority traffic on each of the multiple switches SW on the network 2 via the communication unit 11 (step S11). The control unit 12 obtains the transmission schedules of the switches SW to be scheduled. In the following description, it will be assumed that the control unit 12 has obtained the transmission schedules for switch SW1 (exit port P1), switch SW2 (exit port P2), switch SW3 (exit port P3), and switch SW4 (exit port P4).

[0025] The matrix generation unit 121 creates the scheduling matrix M shown in equation (1) based on the acquired transmission schedule.

[0026]

number

[0027] Here, each row of the scheduling matrix M corresponds to the exit port of a switch SW present in the controlled network, and each column corresponds to the transmission timing of the frame of priority traffic. Any element M of the scheduling matrix M ij (1⁻ᵀ

[0028]

number

[0029] Figure 5 is a table showing the output port and transmission timing for each priority traffic, created based on the scheduling matrix shown in equation (2).

[0030] Switches SW1 to SW4 transmit priority traffic at predetermined transmission timings (t1 to t7) within a synchronized scheduling cycle. The matrix generation unit 121 creates a scheduling matrix showing the transmission timing of priority traffic for each exit port. In the example shown in Figure 5, priority traffic F1 is transmitted from exit port P1 at transmission timing t1. Priority traffic F1 is transmitted from exit port P2 at transmission timing t2, and priority traffic F2 is transmitted at transmission timing t3. Priority traffic F3 is transmitted from exit port P3 at transmission timing t6. Priority traffic F1 is transmitted from exit port P4 at transmission timing t3, priority traffic F2 is transmitted at transmission timing t4, and priority traffic F3 is transmitted at transmission timing t7.

[0031] Referring again to Figure 4, the fragmentation determination unit 122 determines, based on the acquired transmission schedule (table shown in Figure 5), whether or not there is fragmentation at the exit port of one switch SW where there is a gap of a predetermined value or more between the transmission timing of one priority traffic and the transmission timing of the next priority traffic (step S13). Specifically, the control unit 12 refers to the transmission schedule created based on the acquired transmission schedule and determines whether or not there is a gap of one or more transmission timings between the transmission timing of one priority traffic and the transmission timing of the next priority traffic at the exit port of one switch SW.

[0032] One possible method for determining whether there is an available transmission timing is to search a specific row in the scheduling matrix and check whether there is an element of 0 among the elements where priority traffic is stored.

[0033] The fragmentation determination unit 122 determines the presence or absence of fragmentation among the multiple exit ports included in the scheduling matrix, starting with the exit ports with the most scheduled priority traffic. In the example shown in Figure 5, one priority traffic is scheduled for exit port P1, two priority traffic is scheduled for exit port P2, one priority traffic is scheduled for exit port P3, and three priority traffic is scheduled for exit port P4. Therefore, the control unit 12 determines the presence or absence of fragmentation starting from exit port P4. As shown in Figure 5, at exit port P4, there is a gap of two priority traffic transmission timings (transmission timings t5 and t6) between the transmission timing t4 of priority traffic F2 and the transmission timing t7 of priority traffic F3, so the control unit 12 determines that fragmentation is present. Hereafter, the exit port determined to have fragmentation (exit port P4 in the example shown in Figure 5) will be referred to as the target exit port. Furthermore, if the control unit 12 determines that there is no fragmentation at exit port P4, it will then determine the presence or absence of fragmentation at exit port P2, which has the next highest number of scheduled priority traffic after exit port P4.

[0034] The fragmentation determination unit 122 may determine whether fragmentation has occurred, for example, when new priority traffic is added and forwarded via network 2. The fragmentation determination unit 122 may also determine whether fragmentation has occurred, for example, when existing priority traffic is deleted. Furthermore, the fragmentation determination unit 122 may periodically determine whether fragmentation has occurred.

[0035] If the movable traffic determination unit 123 determines that fragmentation exists by the fragmentation determination unit 122, it sets the priority of priority traffic whose transmission timing will be changed in order to perform defragmentation at the target exit port (one exit port) (step S14). Then, the control unit 12 determines whether there is any priority traffic (hereinafter referred to as "movable traffic") among the priority traffic transmitted at the target exit port that can have its transmission timing changed by performing defragmentation (step S15).

[0036] The movable traffic determination unit 123 sets a higher priority for priority traffic whose transmission timing is further from the average transmission timing of all priority traffic transmitted from the target exit port within the cycle time. The movable traffic determination unit 123 then determines whether a priority traffic is movable traffic, starting with the priority traffic with the highest priority. As described above, in the example shown in Figure 5, exit port P4 is the target exit port, and priority traffic F1 is transmitted from exit port P4 at transmission timing t3, priority traffic F2 is transmitted at transmission timing t4, and priority traffic is transmitted at transmission timing t7. Assuming that the transmission timings t1 to t7 are at equal intervals, one example of a method for setting the priority of priority traffic to be moved to eliminate fragmentation is to calculate the average value of the transmission timing of priority traffic in each row of the scheduling matrix and change the transmission timing preferentially starting with the priority traffic furthest from that average. Taking the exit port P4 in Figure 5 as an example, the average value of the transmission timing can be calculated by (t3+t4+t7) / 3.

[0037] The mobile traffic determination unit 123 compares the average value of the obtained transmission timings with the transmission timing of each priority traffic, and determines whether or not the priority traffic with the largest difference is mobile traffic.

[0038] The mobile traffic determination unit 123 may determine whether a priority traffic is mobile traffic from among the priority traffic transmitted from the target exit port, starting with priority traffic whose transmission timing is not included in a cluster of transmission timings of two or more consecutive priority traffics. In the example shown in Figure 5, at exit port P4, priority traffic F1 is transmitted at transmission timing t3, and priority traffic F2 is transmitted at transmission timing t4, which follows transmission timing t3. The transmission timing t7 of priority traffic F3 is not included in the cluster of transmission timings (transmission timings t3 and t4) in which priority traffics F1 and F2 are transmitted consecutively. Therefore, the mobile traffic determination unit 123 may preferentially determine whether a traffic is mobile starting with priority traffic F3.

[0039] As shown in Figure 5, at transmission timings t5 and t6, which are between the transmission timing t4 of priority traffic F2 and the transmission timing t7 of priority traffic F3, the transmission of priority traffic is not scheduled, and the transmission timing of priority traffic F3 can be advanced. Therefore, the mobile traffic determination unit 123 determines that priority traffic F3 is mobile traffic and assumes, for example, as shown in Figure 6, that the transmission timing of priority traffic F3 is changed to transmission timing t5, which is immediately after the transmission timing t4 when priority traffic F2 is transmitted.

[0040] If the mobile traffic determination unit 123 determines that mobile traffic exists, it determines whether or not the overall fragmentation of the network 2 will decrease due to the change in the transmission schedule of each of the multiple switches SW associated with the change in the transmission timing of the mobile traffic (step S16).

[0041] Specifically, the mobile traffic determination unit 123 changes the transmission timing of mobile traffic at other exit ports in accordance with the change in the transmission timing of mobile traffic at the target exit port. As described above, let's assume that the mobile traffic determination unit 123 changes the transmission timing of priority traffic F3, which is mobile traffic, from transmission timing t7 to transmission timing t5. In this case, switch SW3, which is upstream of switch SW4, needs to transmit priority traffic F3 to switch SW4 before transmission timing t5. Therefore, let's assume that the mobile traffic determination unit 123 changes the transmission timing of priority traffic F3 at switch SW3 from transmission timing t6 to transmission timing t4, as shown in Figure 6. Here, at switch SW3, the transmission of priority traffic is not scheduled at transmission timing t4, so even if priority traffic F3 is transmitted at transmission timing t4, no collision with other priority traffic will occur. Therefore, the movable traffic determination unit 123 determines that it is possible to change the transmission timing of priority traffic F3 from transmission timing t6 to transmission timing t4 at switch SW3.

[0042] The increase / decrease measurement unit 124 determines whether the overall fragmentation of network 2 decreases when the transmission timing of mobile traffic at other exit ports is changed in response to a change in the transmission timing of mobile traffic at the target exit port, without conflicting with other priority traffic. In the example shown in Figure 6, no new fragmentation occurs compared to before the transmission scheduling change, and the fragmentation at exit port P4 is eliminated. Therefore, the overall fragmentation of network 2 has decreased.

[0043] If the increase / decrease measurement unit 124 determines that fragmentation will decrease across the entire network 2, the schedule change unit 125 changes the transmission schedule for each of the multiple switches SW according to the assumed change in the transmission timing of mobile traffic (step S17). Then, the schedule change unit 125 transmits the changed transmission schedule to each switch via the communication unit 11.

[0044] Thus, the control unit 12 modifies the transmission schedule for each of the multiple switches SW if, in response to a change in the transmission timing of mobile traffic at the target exit port, the transmission timing of mobile traffic at other exit ports does not conflict with the transmission timing of other priority traffic, and fragmentation decreases for the entire network 2.

[0045] By changing the transmission schedule on each of the multiple switches SW so that fragmentation decreases across the entire network 2, the time available for transmitting BE traffic increases. Therefore, according to the control device 10 and scheduling method of this embodiment, the efficiency of data transfer in network 2 can be improved. Furthermore, according to the control device 10 and scheduling method of this embodiment, by changing the transmission schedule only when fragmentation decreases across the entire network 2, unnecessary changes to the transmission schedule are reduced, and cost increases can be suppressed.

[0046] Note that Figure 6 illustrates an example where no collision occurs with other priority traffic at the destination (transmission timing t4) when the transmission timing of the mobile traffic at exit port P3 is changed. However, collisions with other priority traffic may occur at the destination. For example, as shown in Figure 7, suppose that in addition to priority traffic F3, priority traffic F4 is transmitted from switch SW3 to switch SW4. And, as shown in Figure 8, suppose that priority traffic F4 is transmitted from exit port P3 at transmission timing t4. In this case, if the transmission timing of priority traffic F3 at exit port P3 is changed to transmission timing t4, a collision will occur between priority traffic F3 and priority traffic F4.

[0047] The control unit 12 (movable traffic determination unit 123) may change the transmission timing of movable traffic at other exit ports other than the target exit port in response to a change in the transmission timing of movable traffic at the target exit port, within the allowable delay range for movable traffic (allowable end-to-end delay).

[0048] For example, in the example shown in Figure 8, the priority traffic F3 is allowed to be delayed within a range of two transmission timings. In this case, the control unit 12 determines the transmission timing of the priority traffic F3 at the exit port P3 within a range of two transmission timings (transmission timing t3 or transmission timing t4) from the changed transmission timing t5 of the priority traffic F3 at the exit port P4. As shown in Figure 8, since no transmission of priority traffic is scheduled for transmission timing t3 at the exit port P3, the control unit 12 determines the transmission timing of the priority traffic F3 at the exit port P3 to be transmission timing t3, as shown in Figure 9.

[0049] In this way, by changing the transmission timing of mobile traffic at exit ports other than the target exit port, within the delay range allowed for mobile traffic, scheduling flexibility is improved, and more efficient data transfer becomes possible.

[0050] Next, the hardware configuration of the control device 10 according to this embodiment will be described.

[0051] Figure 10 shows an example of the hardware configuration of the control device 10 according to this embodiment. In Figure 10, an example of the hardware configuration of the control device 10 is shown when the control device 10 is configured with a computer capable of executing program instructions. Here, the computer may be a general-purpose computer, a dedicated computer, a workstation, a PC (personal computer), an electronic notepad, etc. The program instructions may be program code, code segments, etc., for executing the required task.

[0052] As shown in Figure 10, the control device 10 includes a processor 21, ROM (Read Only Memory) 22, RAM (Random Access Memory) 23, storage 24, input unit 25, display unit 26, and communication interface (I / F) 27. Each component is connected to each other via a bus 29 so as to be able to communicate with each other. The processor 21 is specifically a CPU (Central Processing Unit), MPU (Micro Processing Unit), GPU (Graphics Processing Unit), DSP (Digital Signal Processor), SoC (System on a Chip), etc., and may be composed of multiple processors of the same or different types.

[0053] The processor 21 is a control unit that controls each configuration of the control device 10 and performs various arithmetic operations. Specifically, the processor 21 reads a program from the ROM 22 or storage 24 and executes the program using the RAM 23 as a working area. The processor 21 performs the control of each configuration and various arithmetic operations according to the program stored in the ROM 22 or storage 24. In this embodiment, the ROM 22 or storage 24 stores a program that causes the computer to function as the control device 10 according to this disclosure. The configuration of the control device 10 is realized when this program is read and executed by the processor 21.

[0054] The program may be provided in a form stored on a non-transitory storage medium such as a CD-ROM (Compact Disk Read Only Memory), DVD-ROM (Digital Versatile Disk Read Only Memory), or USB (Universal Serial Bus) memory. Alternatively, the program may be provided as a downloadable file from an external device via a network.

[0055] ROM22 stores various programs and data. RAM23 temporarily stores programs or data as a working area. Storage24 consists of an HDD (Hard Disk Drive) or SSD (Solid State Drive) and stores various programs and data, including the operating system.

[0056] The input unit 25 includes a pointing device such as a mouse and a keyboard, and is used for various types of input.

[0057] The display unit 26 is, for example, a liquid crystal display and displays various information. The display unit 26 may also function as an input unit 25 by employing a touch panel system.

[0058] The communication interface 27 is an interface for communicating with other devices (for example, switches SW1 to SW4), and is, for example, an interface for a LAN.

[0059] A computer can be suitably used to function as each part of the control device 10 described above. Such a computer can be realized by storing a program in its memory that describes the processing content for realizing the functions of each part of the control device 10, and by having the computer's processor read and execute this program. In other words, the program can make the computer function as the control device 10 described above. It is also possible to record the program on a non-temporary storage medium. Furthermore, it is possible to provide the program via a network.

[0060] The following additional information is disclosed regarding the embodiments described above.

[0061] [Additional note 1] A method for scheduling the transmission schedule of priority traffic in a network that forwards priority traffic consisting of a series of frames transmitted via multiple switches, with the transmission timing reserved by the switches and the transmission guaranteed to have a maximum delay, The transmission schedule for the priority traffic in each of the aforementioned multiple switches is obtained. Based on the acquired transmission schedule, it is determined whether or not there is fragmentation at the exit port of one switch where there is a gap of a predetermined value or more between the transmission timing of one priority traffic and the transmission timing of the next priority traffic. If it is determined that the aforementioned fragmentation exists, it is determined whether there is any mobile traffic among the priority traffic transmitted at the exit port of the first switch whose transmission timing can be modified by performing defragmentation, thereby reducing the interval between transmissions. If it is determined that the aforementioned mobile traffic exists, it is determined whether the fragmentation of the entire network will decrease due to the change in the transmission schedule of each of the multiple switches resulting from the change in the transmission timing of the aforementioned mobile traffic. A scheduling method that, when it is determined that the fragmentation of the entire network decreases, modifies the transmission schedule of each of the multiple switches.

[0062] [Additional note 2] In the scheduling method described in Appendix 1, A scheduling method that determines whether or not fragmentation has occurred when new priority traffic is added, when existing priority traffic is deleted, or periodically.

[0063] [Additional note 3] In the scheduling method described in Appendix 1 or 2, A scheduling method that determines whether or not fragmentation occurs, starting with the exit ports that have the most scheduled priority traffic.

[0064] [Additional note 4] In the scheduling method described in any one of the appendices 1 to 3, A scheduling method that determines whether a priority traffic is the mobile traffic, starting with the priority traffic whose transmission timing is furthest from the average transmission timing of the priority traffic transmitted at the exit port of the first switch.

[0065] [Additional note 5] In the scheduling method described in any one of the appendices 1 to 4, A scheduling method for determining whether a priority traffic transmitted at the exit port of the aforementioned switch is a mobile traffic, with respect to priority traffic whose transmission timing is not included in a cluster of transmission timings of two or more consecutive priority traffics.

[0066] [Additional note 6] In the scheduling method described in any one of the appendices 1 to 5, A scheduling method for changing the transmission schedule in each of the multiple switches when, as a result of changing the transmission timing of the mobile traffic, the transmission timing of the mobile traffic at other exit ports other than the exit port of one switch does not conflict with the transmission timing of other priority traffic, and the fragmentation of the network as a whole is reduced.

[0067] [Additional note 7] In the scheduling method according to any one of claims 1 to 6, A scheduling method for changing the transmission timing of the mobile traffic within a delay range permissible for the mobile traffic when changing the transmission timing of the mobile traffic at an exit port other than the exit port of the one switch in conjunction with a change in the transmission timing of the mobile traffic.

[0068] [Additional note 8] A control device for controlling the transmission schedule of priority traffic in a network that forwards priority traffic consisting of a series of frames transmitted via multiple switches, with the transmission timing reserved by the switches and the transmission guaranteed to have a maximum delay, Equipped with a control unit, The control unit, Based on the transmission schedule of the priority traffic in each of the aforementioned multiple switches, it is determined whether or not there is fragmentation at the exit port of one switch where there is an interval of a predetermined value or more between the transmission timing of one priority traffic and the transmission timing of the next priority traffic. If it is determined that the aforementioned fragmentation exists, it is determined whether there is any mobile traffic among the priority traffic transmitted at the exit port of the first switch whose transmission timing can be modified by performing defragmentation, thereby reducing the interval between transmissions. If it is determined that the aforementioned mobile traffic exists, it is determined whether the fragmentation of the entire network will decrease due to the change in the transmission schedule of each of the multiple switches resulting from the change in the transmission timing of the aforementioned mobile traffic. A control device that, when it determines that the fragmentation of the entire network is decreasing, modifies the transmission schedule of each of the multiple switches.

[0069] [Additional note 9] A program that causes a computer to execute one of the scheduling methods described in any one of the appendices 1 through 7.

[0070] [Additional Note 10] A storage medium containing the program described in Appendix 9.

[0071] Although the embodiments described above are representative examples, it will be apparent to those skilled in the art that many modifications and substitutions are possible within the spirit and scope of this disclosure. Therefore, the present invention should not be construed as being limited by the embodiments described above, and various modifications or changes are possible without departing from the claims. For example, it is possible to combine multiple component blocks shown in the configuration diagram of the embodiments into one, or to divide one component block. [Explanation of symbols]

[0072] 1,1a Communication System 10 Control device 11 Communications Department 12 Control Unit 21 processors 22 ROM 23 RAM 24 storage 25 Input section 26 Display section 27 Communication I / F 29 bus

Claims

1. A scheduling method by a control device for controlling the transmission schedule of priority traffic in a network that transfers priority traffic consisting of a series of frames transmitted via multiple switches, with the transmission timing reserved by the switches and the transmission timing guaranteed to be maximum delay, wherein the priority traffic is forwarded via multiple switches. The steps include obtaining the transmission schedule for the priority traffic in each of the aforementioned multiple switches, Based on the acquired transmission schedule, the step of determining whether or not there is fragmentation at the exit port of one switch where there is an interval of a predetermined value or more between the transmission timing of one priority traffic and the transmission timing of the next priority traffic, If it is determined that the aforementioned fragmentation exists, the step is to determine whether there is any mobile traffic among the priority traffic transmitted at the exit port of the one switch that can have its interval reduced by performing defragmentation to change the transmission timing, If it is determined that the mobile traffic exists, the step is to determine whether the fragmentation will decrease as a whole network due to the change in the transmission schedule at each of the multiple switches resulting from the change in the transmission timing of the mobile traffic. A scheduling method that includes the step of changing the transmission schedule in each of the multiple switches if it is determined that the fragmentation decreases across the entire network.

2. In the scheduling method described in claim 1, A scheduling method that determines the presence or absence of fragmentation when new priority traffic is added, when existing priority traffic is deleted, or periodically.

3. In the scheduling method described in claim 1, The step of determining whether or not fragmentation occurs is a scheduling method in which the presence or absence of fragmentation is determined starting from the exit port with the largest number of scheduled priority traffics.

4. In the scheduling method described in claim 1, The step of determining whether or not there is movable traffic is a scheduling method in which, among the priority traffic transmitted at the exit port of the one switch, the priority traffic whose transmission timing is furthest from the average transmission timing of the priority traffic transmitted at the exit port of the one switch is determined to be whether or not that priority traffic is movable traffic.

5. In the scheduling method described in claim 1, The step of determining whether or not there is mobile traffic is a scheduling method that determines whether or not a priority traffic is mobile traffic, with respect to priority traffic transmitted at the exit port of one switch whose transmission timing is not included in a cluster of transmission timings of two or more consecutive priority traffics.

6. In the scheduling method described in claim 1, A scheduling method in which the step of changing the transmission schedule is to change the transmission schedule in each of the plurality of switches if, as a result of changing the transmission timing of the mobile traffic, the transmission timing of the mobile traffic at other exit ports other than the exit port of one switch does not conflict with the transmission timing of other priority traffic, and the fragmentation as a whole decreases.

7. In the scheduling method described in claim 1, The step of changing the transmission schedule is a scheduling method that, when changing the transmission timing of the mobile traffic, changes the transmission timing of the mobile traffic at an exit port other than the exit port of the one switch, within a delay range permissible for the mobile traffic.

8. A control device for controlling the transmission schedule of priority traffic in a network that forwards priority traffic consisting of a series of frames transmitted via multiple switches, with the transmission timing reserved by the switches and the transmission guaranteed to have a maximum delay, Equipped with a control unit, The control unit, Based on the transmission schedule of the priority traffic in each of the aforementioned multiple switches, it is determined whether or not there is fragmentation at the exit port of one switch where there is an interval of a predetermined value or more between the transmission timing of one priority traffic and the transmission timing of the next priority traffic. If it is determined that the aforementioned fragmentation exists, it is determined whether there is any mobile traffic among the priority traffic transmitted at the exit port of the first switch whose transmission timing can be modified by performing defragmentation, thereby reducing the interval between transmissions. If it is determined that the aforementioned mobile traffic exists, it is determined whether the fragmentation of the entire network will decrease due to the change in the transmission schedule of each of the multiple switches resulting from the change in the transmission timing of the aforementioned mobile traffic. A control device that, when it determines that the fragmentation of the entire network is decreasing, modifies the transmission schedule of each of the multiple switches.

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