WO2024116389A1

WO2024116389A1 - Communication system, communication control device, communication control method, and program

Info

Publication number: WO2024116389A1
Application number: PCT/JP2022/044469
Authority: WO
Inventors: 尊広久保; 慎一吉原
Original assignee: 日本電信電話株式会社
Priority date: 2022-12-01
Filing date: 2022-12-01
Publication date: 2024-06-06

Abstract

A communication control device 20 comprises: a control unit 22 that preliminarily lists alternative routes available on a network, sets a priority for each of the listed alternative routes, and calculates a preliminary gate control list corresponding to each of the alternative routes in descending order of the priority; and a storage unit 23 that stores a predetermined number of the alternative routes in association with the preliminary gate control list in descending order of the priority, wherein when the network configuration is updated, the control unit 22 acquires a preliminary gate control list corresponding to the updated route from the storage unit 23 and sets the preliminary gate control list in the communication device 10.

Description

COMMUNICATION SYSTEM, COMMUNICATION CONTROL DEVICE, COMMUNICATION CONTROL METHOD, AND PROGRAM

This disclosure relates to a communication system, a communication control device, a communication control method, and a program.

Conventionally, a technology is known in which each node in a network ensures transmission and reception timing and transfers frames of priority traffic according to a gate control list (GCL), which schedules priority traffic on the network to meet delay and jitter requirements.

Non-patent document 1 describes Amendment 25, which specifies enhancements to scheduled traffic in IEEE 802.1Qbv-2015, the IEEE standard for local/metropolitan area networks.

Non-patent document 2 describes the routing algorithm for networks that comply with IEEE 802.1Qbv.

Furthermore, Non-Patent Document 3 discusses how the synthesis of communication schedules for gate control lists defined in IEEE 802.1Qbv can be formulated as a system of constraints expressed via linear array theory (TA).

FIG. 12 is a diagram for explaining changes in the configuration of a network. As shown in FIG. 12, a network in which a gate control list is set in each node may have its configuration changed due to a route failure or physical route switching such as planned route switching. In FIG. 12(i), a planned route switching is performed on a route marked with a "Road Closed" sign, and frames of priority traffic ST (ST#1, #2) are transferred by bypassing the "Road Closed" route. In FIG. 12(ii), a route failure occurs on a route other than the route on which the planned route switching is performed. In FIG. 12(iii), a "Road Closed" is set on the route where the route failure has occurred, and the route for transferring frames of priority traffic ST#1, #2 is changed. In addition to physical route switching, "Road Closed" may be performed by the Spanning Tree Protocol (STP) to avoid logical communication loops.

In this way, when the network configuration is changed, it becomes necessary to update the gate control list so that the delay/jitter requirements are met on the new network. By updating the gate control list, frames of priority traffic ST can be transferred with low delay on the changed network even if the network configuration is changed.

If calculation of the gate control list is started after the network configuration has been changed, frames of priority traffic ST cannot be forwarded with low latency until a solution is found. To solve this problem, it is desirable to store the gate control list calculated with the updated network configuration when the network configuration is changed, so that the gate control list can be quickly set when the network configuration is changed.

However, in addition to the problem that it is difficult to cover all route failure patterns in a network, there is also the problem that memory resources will be insufficient if alternative routes for each route failure pattern are kept as a list, a gate control list for each alternative route is calculated, and all calculated gate control lists are stored in memory one by one as backup gate control lists. In what follows, a gate control list created as a backup to accommodate route switching will be referred to as a backup gate control list.

Therefore, there was room for improvement in the technology for transporting frames of priority traffic on a network.

The purpose of this disclosure, made in light of these circumstances, is to improve the technology for forwarding frames of priority traffic on a network.

In order to solve the above problems, a communication control device according to the present embodiment is a communication control device that causes a communication device to transfer frames of priority traffic, and includes: a control unit that lists alternative routes available on a network in advance, sets priorities for each of the listed alternative routes, and calculates backup gate control lists corresponding to each of the alternative routes in descending order of priority; and a storage unit that associates the alternative routes with the backup gate control lists and stores a predetermined number of them in descending order of priority;
When the configuration of the network is updated, the control unit obtains from the storage unit a backup gate control list corresponding to the updated route and sets the list in the communication device.

In order to solve the above problems, the communication control method according to this embodiment is a communication control method for causing a communication device to forward frames of priority traffic, and includes the steps of: listing alternative routes available on a network in advance by a communication control device; setting a priority for each of the listed alternative routes; calculating a backup gate control list corresponding to each of the alternative routes in descending order of priority; associating the alternative routes with the backup gate control lists and storing a predetermined number of the lists in descending order of priority; and, when the configuration of the network is updated, acquiring the stored backup gate control list corresponding to the updated route and setting it in the communication device.
Execute.

To solve the above problem, the program according to this embodiment causes a computer to function as a communication control device.

This disclosure makes it possible to improve the technology for forwarding frames of priority traffic on a network.

1 is a block diagram showing an example of the configuration of a communication system according to an embodiment of the present invention; FIG. 1 is a diagram showing an example of the configuration of a network connected in a lattice shape. 4 is a flowchart showing an example of a communication control method executed by the communication control device according to the present embodiment. 4 is a flowchart showing an example of a communication control method executed by the communication control device according to the present embodiment. FIG. 1 is a diagram illustrating an update of a network route. FIG. 1 is a diagram for explaining the occurrence of merging of priority traffic. FIG. 13 is a diagram for explaining how to measure the total number of flow nodes of priority traffic. FIG. 13 is a diagram illustrating an example of measuring the total number of flow nodes of priority traffic. 11 is a table illustrating the priority of alternative routes based on the total number of flow nodes. 13 is a table showing a backup gate control list in order of priority of the updated network. 1 is a block diagram showing a schematic configuration of a computer functioning as a communication control device; FIG. 13 is a diagram illustrating a change in the network configuration.

The following describes in detail the embodiments of the present disclosure with reference to the drawings.

(Configuration of communication system)
FIG. 1 is a block diagram showing a configuration example of a communication system according to the present embodiment. With reference to FIG. 1, an overview of a communication system 1 according to an embodiment of the present disclosure will be described. The communication system 1 includes a plurality of communication devices 10 and a communication control device 20. The plurality of communication devices 10 and the communication control device 20 are communicably connected to a network 2 including, for example, the Internet and a mobile communication network. FIG. 2 is a diagram showing a configuration example of a network connected in a lattice shape. In the present disclosure, for example, as shown in FIG. 2, a plurality of communication devices 10 (10A, 10B, 10C, 10D, 10E, 10F, 10G, 10H, 10I, 10J) are connected in a lattice-shaped network 2, but the network topology is not limited thereto. The communication device 10 transmits and receives frames of priority traffic ST (ST#1, ST#2, ST#3, ST#4).

(Configuration of communication device)
The communication device 10 is a network node such as a switch or a router. The communication device 10 includes a communication unit 11, a storage unit 12, and a control unit 13. The communication device 10 executes communication using a Time Aware Shaper (TAS) technology in the Time-Sensitive Networking (TSN) standard. The TAS is a technology for outputting frames via a network 2 according to a gate control list stored in the communication device 10 (set in the communication device 10). A plurality of communication devices 10 are connected to each other on the network 2 so as to be able to communicate with each other, and transfer frames of priority traffic ST based on the control of a communication control device 20.

The communication unit 11 includes one or more communication interfaces that connect to the network 2. The communication interfaces correspond to communication standards such as, but are not limited to, Ethernet (registered trademark), FDDI (Fiber Distributed Data Interface), and Wi-Fi (registered trademark). In this embodiment, the communication unit 11 transmits and receives frames of priority traffic ST.

The storage unit 12 includes one or more memories. The memories are, for example, but not limited to, semiconductor memories, magnetic memories, or optical memories. Each memory included in the storage unit 12 may function, for example, as a main storage device, an auxiliary storage device, or a cache memory. The storage unit 12 stores any information used in the operation of the communication device 10. For example, the storage unit 12 may store system programs, application programs, embedded software, gate control lists, etc. The information stored in the storage unit 12 may be updatable, for example, with information obtained from the network 2 via the communication unit 11.

The control unit 13 includes one or more processors, one or more programmable circuits, one or more dedicated circuits, or a combination of these. The processor is, for example, but is not limited to, a general-purpose processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), or a dedicated processor specialized for a specific process. The programmable circuit is, for example, but is not limited to, an FPGA (Field-Programmable Gate Array). The dedicated circuit is, for example, but is not limited to, an ASIC (Application Specific Integrated Circuit). The control unit 13 controls the operation of the entire communication device 10.

(Configuration of communication control device)
The communication control device 20 includes a communication unit 21, a control unit 22, and a storage unit 23. The communication control device 20 causes the communication device 10 to transfer frames of priority traffic ST.

The communication unit 21 includes one or more communication interfaces that connect to the network 2. The communication interfaces are compatible with standards such as Ethernet (registered trademark), FDDI (Fiber Distributed Data Interface), and Wi-Fi (registered trademark), but are not limited to these and may be compatible with any communication standard. In this embodiment, the communication control device 20 communicates with multiple communication devices 10 via the communication unit 21 and the network 2.

The control unit 22 includes one or more processors, one or more programmable circuits, one or more dedicated circuits, or a combination of these. The control unit 22 controls the operation of the entire communication control device 20.

The storage unit 23 includes one or more memories. Each memory included in the storage unit 23 may function, for example, as a main storage device, an auxiliary storage device, or a cache memory. The storage unit 23 stores any information used in the operation of the communication control device 20. For example, the storage unit 23 may store a system program, an application program, a database, a backup gate control list associated with an alternative route, and the like. The information stored in the storage unit 23 may be updatable, for example, with information obtained from the network 2 via the communication unit 21.

(Operation flow of the communication control device)
3 and 4 are flowcharts showing an example of a communication control method executed by the communication control device according to the present embodiment. The operation of the communication control device 20 according to the present embodiment will be described with reference to FIGS.

Step S101: The control unit 22 sets a gate control list in the communication device 10 via the communication unit 21 and the network 2.

The control unit 13 of each communication device 10 stores the gate control list for the normal network configuration obtained from the communication control device 20 in the memory unit 12.

Step S102: The control unit 22 causes the communication device 10 to forward frames of priority traffic ST.

Each communication device 10 transfers frames of priority traffic ST on the network according to the stored gate control list. The communication device 10 performs communication using TAS (Time Aware Shaper) technology in the TSN (Time-Sensitive Networking) standard. TAS is a technology that outputs frames via the network 2 according to the gate control list stored in the communication device 10.

Step S103: The control unit 22 preliminarily creates a list of alternative routes available on the network.

The control unit 22 searches for available alternative routes within the network in advance and lists them while the network, in which multiple communication devices 10 are communicatively connected, is operating normally. In this disclosure, a list refers to a composite data type (container/collection) that can store multiple pieces of data in an ordered manner. A list in which each piece of data has reference information (link/pointer) indicating the location of the next piece of data is called a linked list, but the list in this disclosure may also be a linked list.

Step S104: The control unit 22 sets a priority for each of the listed alternative routes.

The control unit 22 wants to store backup gate control lists corresponding to all available alternative routes in the storage unit 23. However, since the amount of memory resources available for storing backup gate control lists is limited, it becomes a challenge to set appropriate priorities for the stored alternative routes.

The control unit 22 then calculates the total number of flow nodes, which is the total number of nodes where frames of two or more priority traffic converge, for each alternative route, and sets the priority of the alternative route in descending order of the total number of flow nodes.

Figure 5 is a diagram explaining the updating of network routes. As shown in Figure 5, when the network route through which ST#1 and ST#2 are forwarded is updated, there is a possibility that new merging or demerging of each priority traffic occurs at nodes other than

nodes

1, 2, 3, and 4 where the route switching has occurred. For this reason, the complexity of the calculation of the gate control list for the entire network cannot be understood by looking only at

nodes

1, 2, 3, and 4 related to the route switching.

Figure 6 is a diagram explaining the occurrence of merging of priority traffic ST. As shown in Figure 6, taking priority traffic ST#2 as an example, if we search for cases where merging occurs at nodes other than

nodes

1, 2, 3, and 4 where route switching has occurred, we can see that merging of ST#1 and ST#2 occurs at node a connected to node 1. For this reason, it is necessary to count the increase or decrease in the number of mergings not only at

nodes

1, 2, 3, and 4 involved in the route switching, but also at all the nodes in the updated network.

Therefore, in this disclosure, we compare the total number of flow nodes, which is the sum of the number of merging nodes for each priority traffic, with available alternative routes, and set the priority of the alternative routes in descending order of the total number of flow nodes.

Step S105: The control unit 22 calculates the backup gate control list corresponding to each alternative route in descending order of priority.

Figure 7 explains how to measure the total number of flow nodes for priority traffic. In the network before the update in Figure 7, other priority traffic merges with priority traffic ST#1 at

nodes

3 and 4, and the total number of flow nodes is 2. On the other hand, in the network after the update, other priority traffic merges with priority traffic ST#1 at

nodes

2, 3, and 5, and the total number of flow nodes is 3.

Figure 8 is a diagram explaining an example of measuring the total number of flowing nodes for priority traffic. (i) is the NW before the update, (ii) is NW#1 after the update, and (iii) is NW#2 after the update. Priority traffic ST#1, ST#2, ST#3, and ST#4 are transferred to each network. Below, the total number of flowing nodes in each network is calculated for each priority traffic.

In the network before the update in (i), ST#1 merges with ST#2 at node 3. Also, ST#2 merges with ST#1 at node 3. Therefore, the number of merges for ST#1 is 1, the number of merges for ST#2 is 1, and the total number of flow nodes is 1 + 1 = 2.

In NW#1 after the update in (ii), ST#1 merges with ST#3 at node 3, ST#2 with node 4, and ST#4 with node 6. ST#2 merges with ST#1 at node 4. ST#3 merges with ST#1 at node 3. ST#4 merges with ST#1 at node 6. Therefore, the total number of flow nodes is 3+1+1+1=6.

In NW#2 after the update in (iii), ST#1 merges with ST#2 at node 8. Also, ST#2 merges with ST#1 at node 8. Therefore, the total number of flow nodes is 1+1+0+0=2.

FIG. 9 is a table explaining the priority of alternative routes based on the total number of flow nodes. In this disclosure, a list of alternative routes in a network is held in a field called updated NW#1, #2, .... Then, a priority is assigned based on the result of calculating the total number of flow nodes for each alternative route. In the example shown in FIG. 9, the total number of flow nodes for updated NW#1 is 6, while the total number of flow nodes for updated NW#2 is 2, so the priority of updated NW#1 is set to 1 and the priority of updated NW#2 is set to 2. Note that the priority is set in ascending order of numbers. Then, the backup gate control lists for the alternative routes are calculated in descending order of priority, and the calculated backup gate control lists are stored.

Step S106: The memory unit 23 stores the alternative route in association with the backup gate control list.

FIG. 10 is a table showing the backup gate control list in order of priority of the updated network. The storage unit 23 stores the alternative route and the backup gate control list in association with each other in the list format shown in FIG. 10. In FIG. 10, the updated network configuration corresponds to the alternative route.

Step S107: The control unit 22 determines whether the memory unit 23 has stored all the backup gate control lists.

Step S108: When the storage unit 23 cannot store all the backup gate control lists, it stores only a predetermined number of alternative routes corresponding to the network configuration in descending order of priority.

Step S109: The control unit 22 monitors the occurrence of updates to the configuration of the network 2 consisting of multiple communication devices 10.

The control unit 22 monitors whether an update has occurred to the network configuration, for example, from (i) to (ii) or (iii) as shown in FIG. 8.

Step S110: When the control unit 22 detects an update to the configuration of network 2, it searches for the updated route.

Step S111: The control unit 22 checks whether the memory unit 23 stores an alternative route that corresponds to the updated route.

Step S112: If the memory unit 23 does not store an alternative route corresponding to the updated route, the control unit 22 calculates a gate control list corresponding to the updated route.

Step S113: When the network configuration is updated, if the memory unit 23 stores an alternative route corresponding to the updated route, the control unit 22 obtains from the memory unit 23 a backup gate control list corresponding to the updated route.

Step S114: The control unit 22 obtains the newly calculated gate control list or the spare gate control list stored in the memory unit 23, and sets it in the communication device 10.

The control unit 22 obtains the newly calculated gate control list or the spare gate control list stored in the memory unit 23, and sets it in each communication device 10. When the network configuration is updated, each communication device 10 needs to update the gate control list so as to satisfy the delay and jitter requirements on the new network. By updating the gate control list, each communication device 10 becomes able to forward priority traffic by TAS on the new network.

Step S115: The control unit 22 determines whether or not the forwarding of priority traffic by multiple communication devices 10 will continue.

If the forwarding of priority traffic by multiple communication devices 10 is to continue, the control unit 22 returns to step S102, and if the forwarding is to end, the control unit 22 ends the process.

In addition, each time the network configuration is updated (an update is detected), the control unit 22 updates the list of alternative routes corresponding to the updated network configuration, updates the priority of each updated alternative route, and calculates a backup gate control list corresponding to each updated alternative route in descending order of priority.

As described above, the communication control device 20 according to this embodiment makes a list of alternative routes available on the network, sets a priority for each of the listed alternative routes, calculates a backup gate control list corresponding to each of the alternative routes in order of decreasing priority, associates the alternative routes with the backup gate control lists, and stores a predetermined number of them in order of decreasing priority in the memory unit 23. When the network configuration is updated, the backup gate control list corresponding to the updated route is obtained from the memory unit 23 and set in the communication device 10.

The present invention saves memory resources by pre-calculating the number of priority traffic merging points for alternative routes in advance, assuming a network failure, and storing backup gate control lists preferentially for nodes with a large number of merging points.

With this configuration, when updating a network route, instead of reactive processing of recalculating the gate control list after the update, it is possible to perform proactive processing of quickly setting the backup gate control list corresponding to the updated route in the communication device 10 by storing the backup gate control list of the alternative route available on the network as a list in advance. This improves the technology for forwarding frames of priority traffic on a network in that it reduces the likelihood of delays in the restoration of low-latency services due to the time taken to calculate the gate control list.

The above-mentioned embodiments have been described as representative examples, but it will be apparent to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited by the above-mentioned embodiments, and various modifications or changes are possible without departing from the scope of the claims. For example, it is possible to combine multiple configuration blocks shown in the configuration diagram of the embodiment into one, or to divide one configuration block.

In this disclosure, the total number of flow nodes, which is the sum of the number of merging nodes for each priority traffic, is compared with the number of total flow nodes for available alternative routes, and the priority of the alternative routes is set in order of the number of total flow nodes. However, the index for setting the priority is not limited to the total number of flow nodes, and centralities such as degree centrality, closeness centrality, eigenvector centrality, and betweenness centrality may also be used. Centrality is an index that indicates the importance of each node in the network.

Degree centrality is an index of the degree of each node (the number of edges connected to that node). According to degree centrality, the more nodes a node is adjacent to, the more important it is evaluated as. Closeness centrality is an index of the inverse of the average distance (length of the shortest path) from a node to all other nodes. According to closeness centrality, the smaller the sum of the distances to other nodes, the more important a node is evaluated as. Eigenvector centrality is an index that reflects the centrality of other nodes related to a node in the centrality of a node. According to eigenvector centrality, the centrality of each node is proportional to the sum of the centralities of the nodes adjacent to each node. Betweenness centrality is an index of the percentage of a node that is included in the shortest path between two other nodes. According to betweenness centrality, the more shortest paths that pass through a node, the more important a node is evaluated as.

In order to function the above-mentioned communication control device 20, it is also possible to use a computer capable of executing program instructions. FIG. 11 is a block diagram showing a schematic configuration of a computer 100 functioning as the communication control device 20. Here, the computer 100 functioning as the communication control device 20 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 performing the required tasks.

As shown in FIG. 11, the computer 100 comprises a processor 110, a memory unit including a ROM (Read Only Memory) 120, a RAM (Random Access Memory) 130, and a storage 140, an input unit 150, an output unit 160, and a communication interface (I/F) 170. Each component is connected to each other so as to be able to communicate with each other via a data bus 180.

ROM 120 stores various programs and various data. RAM 130 temporarily stores programs or data as a working area. Storage 140 is composed of a HDD (Hard Disk Drive) or SSD (Solid State Drive), and stores various programs and various data including an operating system. In this disclosure, the programs related to this disclosure are stored in ROM 120 or storage 140.

The processor 110 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. The processor 110 reads programs from the ROM 120 or storage 140, and executes the programs using the RAM 130 as a working area, thereby controlling each of the above components and performing various arithmetic processing. At least a portion of these processing contents may be realized by hardware.

The program may be recorded on a recording medium that can be read by the communication control device 20. If such a recording medium is used, it can be installed in the communication control device 20. Here, the recording medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a CD-ROM, a DVD-ROM, or a USB (Universal Serial Bus) memory. In addition, the program may be in a form that is downloaded from an external device via a network.

The following notes are further provided with respect to the above embodiment.

(Additional Note 1)
A communication control device that causes a communication device to transfer a frame of priority traffic,
a control unit that lists alternative routes available on the network in advance, sets priorities for each of the listed alternative routes, and calculates backup gate control lists corresponding to each of the alternative routes in descending order of priority;
a storage unit that stores a predetermined number of the alternative routes and the backup gate control list in order of decreasing priority, in association with each other;
When the configuration of the network is updated, the control unit obtains a backup gate control list corresponding to the updated route from the storage unit and sets the list in the communication device.
The control unit calculates a total flow node number, which is the total number of nodes where frames of two or more priority traffic converge, for each of the alternative routes, and sets the priority of the alternative routes in order of the largest total flow node number.
(Additional Note 3)
The control unit of the communication control device described in

appendix

1 or 2 updates a list of alternative routes corresponding to the updated network configuration, updates the priority of each updated alternative route, and calculates a backup gate control list corresponding to each of the updated alternative routes in order of highest priority each time the network configuration is updated.
(Additional Note 4)
A communication system comprising: a communication control device according to any one of claims 1 to 3; and a plurality of communication devices that are communicatively connected to each other on a network and forward frames of priority traffic based on the control of the communication control device.
(Additional Note 5)
A communication control method for causing a communication device to transfer a frame of priority traffic, comprising the steps of:
The communication control device
A communication control method in which alternative routes available on a network are listed in advance, a priority is set for each of the listed alternative routes, a backup gate control list corresponding to each of the alternative routes is calculated in order of decreasing priority, the alternative routes are associated with the backup gate control lists, and a predetermined number of the backup gate control lists are stored in order of decreasing priority, and when the configuration of the network is updated, the stored backup gate control list corresponding to the updated route is obtained and set in the communication device.
(Additional Note 6)
A non-transitory storage medium storing a program executable by a computer, the non-transitory storage medium storing a program that causes the computer to function as a communication control device described in any one of appended claims 1 to 3.

1 Communication system 2

Networks

10, 10A to 10J Communication device 11 Communication section 12 Storage section 13 Control section 20 Communication control device 21 Communication section 22 Control section 23 Storage section

Claims

A communication control device that causes a communication device to transfer a frame of priority traffic,
a control unit that lists alternative routes available on the network in advance, sets priorities for each of the listed alternative routes, and calculates backup gate control lists corresponding to each of the alternative routes in descending order of priority;
a storage unit that stores a predetermined number of the alternative routes and the backup gate control list in order of decreasing priority, in association with each other;
When a configuration of the network is updated, the control unit obtains from the storage unit a backup gate control list corresponding to the updated route and sets the list in the communication device.
The communication control device according to claim 1, wherein the control unit calculates, for each of the alternative routes, a total number of flow nodes, which is the total number of nodes at which frames of two or more priority traffics converge, and sets the priority of the alternative routes in descending order of the total number of flow nodes.
The communication control device according to claim 1 or 2, wherein the control unit updates a list of alternative routes corresponding to the updated network configuration, updates the priority of each of the updated alternative routes, and calculates a backup gate control list corresponding to each of the updated alternative routes in descending order of priority each time the network configuration is updated.
A communication control device according to claim 1 or 2,
a plurality of communication devices connected to each other on a network so as to be able to communicate with each other, and each of which transfers frames of prioritized traffic under the control of the communication control device;
A communication system comprising:
A communication control method for causing a communication device to transfer a frame of priority traffic, comprising the steps of:
The communication control device
pre-listing alternative routes available on the network;
setting a priority for each of the listed alternative routes;
calculating backup gate control lists corresponding to each of the alternative paths in descending order of priority;
a step of storing a predetermined number of the alternative routes and the backup gate control list in order of decreasing priority in association with each other;
When the configuration of the network is updated, a backup gate control list corresponding to the updated route is acquired and set in the communication device;
A communication control method for performing the above.
A program for causing a computer to function as the communication control device according to claim 1 or 2.