Backup method and device, electronic equipment and storage medium

Abstract

The invention provides a backup method and device, electronic equipment and a storage medium, the method is applied to first firewall equipment serving as main equipment in a backup group, the backup group further comprises second firewall equipment serving as standby equipment, and the method comprises the following steps: generating a pairing request message, and broadcasting the pairing request message in a current subnet; when a pairing response message returned by the second firewall device is received, creating an RBM channel between the first firewall device and the second firewall device; and synchronizing the key configuration information, the service table item information and the RBM system state information based on the RBM channel. According to the method, the RBM channel is realized between the two firewall devices by applying the wireless transmission technology, the occupation of device interface resources is reduced, and the influence of actual physical connection line damage on the transmission efficiency is reduced.

Description

Technical Field

[0001] The present application relates to the field of communication technology, and in particular to a backup method, device, electronic device and storage medium. Background Art

[0002] In modern network security systems, firewalls are a key link. To ensure high availability, two firewall devices are usually deployed at key locations in the network to back up each other. Remote Backup Management (RBM) technology can achieve dual-machine hot standby. RBM technology provides an RBM channel for information synchronization between two devices, but currently the RBM channel is mainly implemented by multiple actual physical connections and interfaces between the two devices. This implementation method will occupy the interface resources of the device, and the actual physical connection is easy to damage, affecting the channel transmission efficiency, and will also increase the complexity of device wiring. Summary of the invention

[0003] In order to overcome the problems existing in the related art, the present application provides a backup method, device, electronic device and storage medium.

[0004] According to a first aspect of an embodiment of the present application, a backup method is provided, the method being applied to a first firewall device as a primary device in a backup group, the backup group also including a second firewall device as a backup device, the method comprising:

[0005] Generate a pairing request message including a backup key and a first address, and broadcast the pairing request message in the current subnet, wherein the first address is an IP address of a virtual interface of the first firewall device;

[0006] Upon receiving a pairing response message, determining whether the backup key and IP address included in the pairing response message are the same as the backup key and second address recorded locally, wherein the second address is the IP address of the virtual interface of the second firewall device, the first address and the second address belong to the same subnet segment, and the pairing response message is generated and sent to the first firewall device by the second firewall device after determining that the backup key and IP address included in the pairing request message are the same as the backup key and first IP address recorded by the second firewall device;

[0007] If the judgment result is yes, creating a remote backup management RBM channel between the first firewall device and the second firewall device according to the first address and the second address;

[0008] Based on the RBM channel, key configuration information, service item information, and RBM system status information are synchronized between the first firewall device and the second firewall device.

[0009] According to a second aspect of an embodiment of the present application, a backup device is provided, the device being applied to a first firewall device as a primary device in a backup group, the backup group also including a second firewall device as a backup device, the device comprising:

[0010] a pairing request module, configured to generate a pairing request message including a backup key and a first address, and broadcast the pairing request message in a current subnet, wherein the first address is an IP address of a virtual interface of the first firewall device;

[0011] a judgment module, configured to judge, upon receiving a pairing response message, whether a backup key and an IP address included in the pairing response message are the same as a backup key and a second address recorded locally, wherein the second address is an IP address of a virtual interface of the second firewall device, the first address and the second address belong to the same subnet segment, and the pairing response message is generated and sent to the first firewall device by the second firewall device after determining that the backup key and the IP address included in the pairing request message are the same as the backup key and the first IP address recorded by the second firewall device;

[0012] A creation module, configured to create a remote backup management RBM channel between the first firewall device and the second firewall device according to the first address and the second address when the judgment result is yes;

[0013] A synchronization module is used to synchronize key configuration information, service item information, and RBM system status information between the first firewall device and the second firewall device based on the RBM channel.

[0014] According to a third aspect of an embodiment of the present application, there is provided an electronic device, comprising a processor and a machine-readable storage medium, wherein the machine-readable storage medium stores machine-executable instructions that can be executed by the processor, and the processor is prompted by the machine-executable instructions to implement the steps of the backup method described above.

[0015] According to a fourth aspect of an embodiment of the present application, a computer-readable storage medium is provided, wherein a computer program is stored in the computer-readable storage medium, and when the computer program is executed by a processor, the steps of the backup method described above are implemented.

[0016] The technical solution provided by the embodiments of the present application may have the following beneficial effects:

[0017] In an embodiment of the present application, an RBM channel is implemented by applying wireless transmission technology between two firewall devices, and synchronization of key configuration information, service table information and RBM system status information between the two firewall devices is achieved based on the RBM channel, thereby reducing the occupancy of device interface resources to a certain extent, reducing the impact of actual physical connection damage on transmission efficiency, ensuring the reliability and security of data transmission, and reducing the complexity of device wiring.

[0018] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated in the specification and constitute a part of this application, illustrate embodiments consistent with the application and, together with the description, serve to explain the principles of the application.

[0020] Figure 1 A first flow chart of a backup method provided in an embodiment of the present application;

[0021] Figure 2 A process diagram of a backup method provided in an embodiment of the present application;

[0022] Figure 3 A second flow chart of a backup method provided in an embodiment of the present application;

[0023] Figure 4 A schematic diagram of a backup device provided in an embodiment of the present application;

[0024] Figure 5 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0025] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0026] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms of "a", "said" and "the" used in this application and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0027] It should be understood that, although the terms first, second, third, etc. may be used in the present application to describe various information, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the words "if" or "if" as used herein may be interpreted as "at the time of" or "when...".

[0028] In modern network security systems, in order to ensure high availability, two devices are generally deployed at key locations in the network to reduce the risk of network interruption due to single point failure of the device and improve network reliability. For traditional network devices (such as switches and routers), it is only necessary to ensure the redundancy of the Layer 2 network and the backup of routing table items to ensure uninterrupted transmission of services. However, for devices that need to perform status detection and policy processing on messages (such as firewalls, intrusion prevention, web firewalls, Internet behavior auditing, etc.), such devices will perform a legitimacy check on the first packet of a flow. If the check passes, a session is established. Subsequent packets of the flow will no longer be subject to legitimacy checks. They only need to match the session to forward the message, otherwise the packet will be discarded. Therefore, when deploying such devices for reliability, it is also necessary to ensure the consistency of the service table information and key configuration information between the two devices. Only in this way can the uninterrupted transmission of services be guaranteed.

[0029] RBM technology can solve the above problems and ensure the consistency of configuration information and service entry information on the active and standby devices. RBM technology provides an RBM channel to transmit the operating status information, key configuration information and service entry information of the RBM system between the two devices. However, the RBM channel is currently mainly implemented by multiple actual physical lines and interfaces between the two devices.

[0030] Next, the embodiments of the present application are described in detail.

[0031] The embodiment of the present application provides a backup method, which is applied to a first firewall device as a primary device in a backup group, and the backup group also includes a second firewall device as a backup device. Figure 1 As shown, the method may include the following steps:

[0032] Step 110: Generate a pairing request message including a backup key and a first address, and broadcast the pairing request message in the current subnet;

[0033] The first address mentioned above refers to the IP address of the virtual interface of the first firewall device.

[0034] Step 120: upon receiving the pairing response message, determine whether the backup key and IP address included in the pairing response message are the same as the backup key and second address recorded locally; if the determination result is yes, proceed to the next step, otherwise, do not process;

[0035] The second address is the IP address of the virtual interface of the second firewall device. It should be noted that the first address and the second address belong to the same subnet segment.

[0036] The pairing response message is generated and sent to the first firewall device by the second firewall device after determining that the backup key and IP address included in the pairing request message are the same as the backup key and first IP address recorded by the second firewall device.

[0037] Step 130: Create a remote backup management RBM channel between the first firewall device and the second firewall device according to the first address and the second address;

[0038] Step 140: Based on the RBM channel, synchronize key configuration information, service item information, and RBM system status information between the first firewall device and the second firewall device.

[0039] To create an RBM channel, the embodiment of the present application creates a virtual interface on each of the two firewall devices and configures the IP address of the virtual interface, so that the virtual interfaces of the two firewall devices are in the same subnet. Specifically, the embodiment of the present application pre-creates a virtual interface on the first firewall device and configures the IP address of the virtual interface to obtain a first address, and creates a virtual interface on the second firewall device and configures the IP address of the virtual interface to obtain a second address, and the first address and the second address are in the same subnet segment. For example, the virtual interface IP of the first firewall device is configured as 192.168.1.1 / 30, and the virtual interface IP of the second firewall device is configured as 192.168.1.2 / 30.

[0040] For the first firewall device, the first address is the local address of the RBM channel to be created. Therefore, the embodiment of the present application will also specify the peer address of the RBM channel to be created on the first firewall device as the second address, that is, specify the IP address of the virtual interface of the second firewall device on the first firewall device. Similarly, for the second firewall device, the second address is the local address of the RBM channel to be created. The embodiment of the present application will specify the peer address of the RBM channel to be created on the second firewall device as the first address, that is, specify the IP address of the virtual interface of the first firewall device on the second firewall device.

[0041] In addition, the embodiment of the present application also configures a backup key on the two firewall devices, and the backup key on the first firewall device is the same as the backup key on the second firewall device. One function of the backup key is to be used for pairing between the two firewall devices, and another function is to be used to encrypt the synchronization data between the two firewall devices to ensure that the synchronization data is only transmitted between the two firewall devices connected by the RBM channel. Specifically, the pairing key can be a 64-bit key.

[0042] Finally, the embodiment of the present application also specifies the roles of the two firewall devices in the backup group, that is, specifies whether each firewall device is a primary device or a backup device in the backup group. The embodiment of the present application is described with the first firewall device as the primary device.

[0043] After the above configuration, if Figure 2 As shown, the first firewall device generates a pairing request message including a backup key and a first address, and broadcasts the pairing request message in the current subnet through wireless technology to find the device where the second address is located. After receiving the above pairing request message, the second firewall device first verifies whether the backup key and IP address included in the pairing request message are the same as the backup key and the first IP address recorded by the second firewall device. Pairing is allowed only when the backup key and the IP address are the same. Specifically, if they are the same, a pairing response message including the backup key and the second address is generated and sent to the first firewall device; if they are not the same, no processing is performed.

[0044] like Figure 2 As shown, after receiving the pairing response message, the first firewall device first verifies whether the backup key and IP address included in the pairing response message are the same as the backup key and second address recorded locally. Only when the backup key and IP address are the same, pairing is allowed. Specifically, if the verification result is yes, a remote backup management RBM channel is created between the first firewall device and the second firewall device according to the first address and the second address, otherwise no processing is performed.

[0045] At this point, the RBM channel is created. Based on the RBM channel, the first firewall device synchronizes key configuration information, service item information, and RBM system status information between the first firewall device and the second firewall device.

[0046] The embodiment of the present application synchronizes the service table information of the active device to the standby device based on the RBM channel to ensure that no service interruption occurs after the active-standby switch. Specifically, in the embodiment of the present application, the service table information synchronized between the first firewall device and the second firewall device may include the following: session table items, session association table items, load balancing continuity table items, proximity table items, and domain name system table items.

[0047] In the embodiment of the present application, the key configuration information on the first firewall device as the main device is backed up to the second firewall device as the backup device based on the RBM channel, and the corresponding configuration information on the second firewall device as the backup device is overwritten to ensure that the key configuration information is completely consistent on the main and backup devices, avoiding the service interruption problem caused by the lack of corresponding configuration information on the new main device during the main-backup switching. Specifically, in the embodiment of the present application, the key configuration information synchronized between the first firewall device and the second firewall device may include the following: firewall default policy, log function parameters, firewall mode (such as routing mode, transparent mode, hybrid mode, etc.), firewall interface configuration, network address translation configuration, VPN configuration, high availability settings, attack protection settings, etc.

[0048] To ensure reliability, as a preferred implementation, after creating the RBM channel, the first firewall device will also create an RBM backup channel to achieve dual-channel redundant configuration. The primary and backup RBM channels back up the transmission data to prevent data transmission interruption or abnormality between the two firewall devices when the RBM channel is abnormal. When the RBM channel is abnormal, the RBM backup channel takes over the transmission task. The two RBM channels can also perform data transmission as backup for each other as the primary channel at the same time, thereby improving transmission efficiency.

[0049] As a specific implementation method, Figure 3 As shown, the first firewall device can also implement the following steps:

[0050] Step 310: Create an RBM backup channel between the first firewall device and the second firewall device according to the first address and the second address;

[0051] Step 320: When the RBM channel is abnormal, based on the RBM backup channel, the key configuration information, service item information and RBM system status information between the first firewall device and the second firewall device are synchronized.

[0052] In order to ensure the integrity of data transmission during the data transmission process, as a preferred implementation, the second firewall device locally generates an integrity check value for the synchronization data at intervals of a certain time period or each time data of a certain size is transmitted, and the generated integrity check value is compared with the received integrity check value. If the comparison is consistent, it indicates that the synchronization data is complete and normal, otherwise it is abnormal. When the verification result is abnormal, the second firewall device sends a message to the first firewall device to retransmit the data.

[0053] As a specific implementation, the second firewall device performs integrity check on the synchronization data when preset conditions are met, where the preset conditions are that the size of the synchronization data reaches a preset size, the synchronization duration reaches a preset duration, or an integrity check command is received.

[0054] As a specific implementation method, the process of creating an RBM channel specifically includes the following steps: the first firewall device sends a TCP connection request and a channel detection message to the second firewall device according to the first address and the second address; after receiving the TCP connection request and the channel detection message, the second firewall device determines that the channel between the two has been created and performs a channel detection to detect whether the channel is normal, and then generates a detection response message and sends it to the first firewall device; after receiving the detection response message, the first firewall device determines that the remote backup management RBM channel between the first firewall device and the second firewall device is successfully created.

[0055] As a specific implementation method, the first firewall device determines its role in the backup group in the following manner: when the first address is smaller than the second address, determines its role in the backup group as a primary device, and determines the role of the second firewall device in the backup group as a backup device; or, based on the role configuration information, determines its role in the backup group as a primary device, and determines the role of the second firewall device in the backup group as a backup device.

[0056] As a specific implementation method, the process of synchronizing information based on the RBM channel specifically includes: using the backup key as the data stream prefix, encapsulating the key configuration information, business table item information and RBM system status information into a data stream; transmitting the data stream to the second firewall device through the RBM channel, so that the second firewall device performs a data synchronization operation according to the data stream after determining that the data stream prefix of the data stream is the same as the backup key recorded by the second firewall device, so as to achieve synchronization of the key configuration information, business table item information and RBM system status information between the first firewall device and the second firewall device.

[0057] It can be seen from the above technical solutions that the embodiment of the present application applies wireless transmission technology between two firewall devices to realize the RBM channel, and realizes the synchronization of key configuration information, service table information and RBM system status information between the two firewall devices based on the RBM channel. Compared with the wired implementation scheme of the RBM channel, this wireless implementation scheme of the RBM channel reduces the occupation of device interface resources, reduces the impact of actual physical connection damage on transmission efficiency, and reduces the complexity of device wiring.

[0058] Based on the same inventive concept, the present application also provides a backup device, which is applied to a first firewall device as a primary device in a backup group, and the backup group also includes a second firewall device as a backup device.

[0059] like Figure 4 As shown, the backup device in the embodiment of the present application specifically includes:

[0060] A pairing request module 410, configured to generate a pairing request message including a backup key and a first address, and broadcast the pairing request message in a current subnet, wherein the first address is an IP address of a virtual interface of the first firewall device;

[0061] The judgment module 420 is used to judge whether the backup key and the IP address included in the pairing response message are the same as the backup key and the second address recorded locally when receiving the pairing response message, wherein the second address is the IP address of the virtual interface of the second firewall device, the first address and the second address belong to the same subnet segment, and the pairing response message is generated by the second firewall device after determining that the backup key and the IP address included in the pairing request message are the same as the backup key and the first IP address recorded by the second firewall device, and sent to the first firewall device;

[0062] A creation module 430, configured to create a remote backup management RBM channel between the first firewall device and the second firewall device according to the first address and the second address when the judgment result is yes;

[0063] The synchronization module 440 is used to synchronize key configuration information, service item information, and RBM system status information between the first firewall device and the second firewall device based on the RBM channel.

[0064] As a specific implementation, the device further includes:

[0065] A first configuration module, used to create a virtual interface and configure an IP address of the virtual interface to obtain a first address;

[0066] A second configuration module, used to obtain the IP address of the virtual interface of the second firewall device to obtain a second address;

[0067] The third configuration module is used to configure the backup key.

[0068] As a specific implementation, the device further includes:

[0069] a redundancy creation module, configured to create an RBM backup channel between the first firewall device and the second firewall device according to the first address and the second address;

[0070] A redundant synchronization module is used to synchronize key configuration information, service table information and RBM system status information between the first firewall device and the second firewall device based on the RBM backup channel when the RBM channel is abnormal.

[0071] As a specific implementation, the creation module 430 specifically includes:

[0072] A first creation unit, configured to send a TCP connection request and a channel detection message to the second firewall device according to the first address and the second address;

[0073] The second creation unit is used to determine that the remote backup management RBM channel between the first firewall device and the second firewall device is successfully created after receiving the detection response message returned by the second firewall device.

[0074] As a specific implementation, the device further includes:

[0075] A role determination module, used to determine its own role in the backup group in the following manner: when the first address is smaller than the second address, determining its own role in the backup group as a primary device, and determining the role of the second firewall device in the backup group as a backup device; or, based on role configuration information, determining its own role in the backup group as a primary device, and determining the role of the second firewall device in the backup group as a backup device.

[0076] As a specific implementation, the synchronization module 440 specifically includes:

[0077] A first synchronization unit, configured to encapsulate key configuration information, service entry information, and RBM system status information into a data stream using the backup key as a data stream prefix;

[0078] A second synchronization unit is used to transmit the data stream to the second firewall device through the RBM channel, so that the second firewall device performs a data synchronization operation according to the data stream after determining that the data stream prefix of the data stream is the same as the backup key recorded by the second firewall device, so as to achieve synchronization of key configuration information, business table item information and RBM system status information between the first firewall device and the second firewall device.

[0079] The present application also provides an electronic device, such as Figure 5 As shown, it includes a processor 510 and a machine-readable storage medium 520, wherein the machine-readable storage medium 520 stores machine-executable instructions that can be executed by the processor 510, and the processor 510 is prompted by the machine-executable instructions to implement the steps of any of the above backup methods.

[0080] The machine-readable storage medium may include a random access memory (RAM) or a non-volatile memory (NVM), such as at least one disk storage. Optionally, the machine-readable storage medium may also be at least one storage device located away from the processor.

[0081] The above-mentioned processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components.

[0082] In another embodiment provided in the present application, a computer-readable storage medium is provided, in which a computer program is stored. When the computer program is executed by a processor, the steps of any of the above backup methods are implemented.

[0083] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A backup method, characterized in that: The method is applied to a first firewall device as a primary device in a backup group, wherein the backup group also includes a second firewall device as a backup device, and the method includes: Generate a pairing request message including a backup key and a first address, and broadcast the pairing request message in the current subnet, wherein the first address is an IP address of a virtual interface of the first firewall device; Upon receiving a pairing response message, determining whether the backup key and IP address included in the pairing response message are the same as the backup key and second address recorded locally, wherein the second address is the IP address of the virtual interface of the second firewall device, the first address and the second address belong to the same subnet segment, and the pairing response message is generated and sent to the first firewall device by the second firewall device after determining that the backup key and IP address included in the pairing request message are the same as the backup key and first IP address recorded by the second firewall device; If the judgment result is yes, creating a remote backup management RBM channel between the first firewall device and the second firewall device according to the first address and the second address; Based on the RBM channel, key configuration information, service item information, and RBM system status information are synchronized between the first firewall device and the second firewall device.

2. The method according to claim 1, characterized in that: Before generating the pairing request message including the backup key and the first address, the method further includes: Create a virtual interface and configure an IP address of the virtual interface to obtain a first address; Obtaining the IP address of the virtual interface of the second firewall device to obtain a second address; Configure the backup key.

3. The method according to claim 1, characterized in that After creating a remote backup management RBM channel between the first firewall device and the second firewall device according to the first address and the second address, the method further includes: Creating an RBM backup channel between the first firewall device and the second firewall device according to the first address and the second address; When the RBM channel is abnormal, key configuration information, service item information, and RBM system status information between the first firewall device and the second firewall device are synchronized based on the RBM backup channel.

4. The method according to claim 1, characterized in that: Creating a remote backup management RBM channel between the first firewall device and the second firewall device according to the first address and the second address specifically includes: Sending a TCP connection request and a channel detection message to the second firewall device according to the first address and the second address; After receiving the detection response message returned by the second firewall device, it is determined that the remote backup management RBM channel between the first firewall device and the second firewall device is successfully established.

5. The method according to claim 1, characterized in that The method further comprises: The role of the backup group is determined by: When the first address is smaller than the second address, determining the role of the firewall device in the backup group as a master device, and determining the role of the second firewall device in the backup group as a backup device; or, According to the role configuration information, it is determined that its role in the backup group is a master device, and it is determined that the role of the second firewall device in the backup group is a backup device.

6. The method according to claim 1, characterized in that Based on the RBM channel, synchronizing key configuration information, service item information, and RBM system status information between the first firewall device and the second firewall device, specifically including: Using the backup key as a data stream prefix, key configuration information, service table item information, and RBM system status information are encapsulated into a data stream; The data stream is transmitted to the second firewall device through the RBM channel, so that the second firewall device performs a data synchronization operation according to the data stream after determining that the data stream prefix of the data stream is the same as the backup key recorded by the second firewall device, so as to achieve synchronization of key configuration information, business table item information and RBM system status information between the first firewall device and the second firewall device.

7. A backup device, characterized in that: The device is applied to a first firewall device as a primary device in a backup group, the backup group also includes a second firewall device as a backup device, and the device includes: a pairing request module, configured to generate a pairing request message including a backup key and a first address, and broadcast the pairing request message in a current subnet, wherein the first address is an IP address of a virtual interface of the first firewall device; a judgment module, configured to judge, upon receiving a pairing response message, whether a backup key and an IP address included in the pairing response message are the same as a backup key and a second address recorded locally, wherein the second address is an IP address of a virtual interface of the second firewall device, the first address and the second address belong to the same subnet segment, and the pairing response message is generated and sent to the first firewall device by the second firewall device after determining that the backup key and the IP address included in the pairing request message are the same as the backup key and the first IP address recorded by the second firewall device; A creation module, configured to create a remote backup management RBM channel between the first firewall device and the second firewall device according to the first address and the second address when the judgment result is yes; A synchronization module is used to synchronize key configuration information, service item information, and RBM system status information between the first firewall device and the second firewall device based on the RBM channel.

8. The device according to claim 7, characterized in that The device also includes: a redundancy creation module, configured to create an RBM backup channel between the first firewall device and the second firewall device according to the first address and the second address; A redundant synchronization module is used to synchronize key configuration information, service table information and RBM system status information between the first firewall device and the second firewall device based on the RBM backup channel when the RBM channel is abnormal.

9. An electronic device, characterized in that: The method comprises a processor and a machine-readable storage medium, wherein the machine-readable storage medium stores machine-executable instructions that can be executed by the processor, and the processor is prompted by the machine-executable instructions to implement the method steps described in any one of claims 1 to 6.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method steps of any one of claims 1 to 6 are implemented.

Images