WO2024066967A1 - Method and apparatus for realizing ethernet ring network protection in tsn virtual bridge - Google Patents

Abstract

The embodiments of the present disclosure provide a method for realizing Ethernet ring network protection in a TSN virtual bridge. The method comprises: a TSN virtual bridge deployed in an Ethernet ring network receiving a mapping table of a fault identifier and a TSN scheduling parameter that is issued by a TSN control management unit; the TSN virtual bridge adjusting the TSN scheduling parameter in the mapping table to a scheduling parameter of a corresponding network element in the TSN virtual bridge, and issuing the adjusted mapping table to the corresponding network element; and after the corresponding network element receives a state notification message triggered by the fault of the Ethernet ring network, applying the corresponding scheduling parameter according to the fault identifier carried in the state notification message.

Description

Method and device for implementing Ethernet ring network protection in TSN virtual bridge

CROSS-REFERENCE TO RELATED APPLICATIONS

The present disclosure is based on Chinese patent application No. 202211192919.6 filed on September 28, 2022, entitled “Method and Device for Implementing Ethernet Ring Network Protection in TSN Virtual Bridge”, and claims the priority of the patent application, and all the contents disclosed therein are incorporated into the present disclosure by reference.

Technical Field

The disclosed embodiments relate to the field of communications, and more specifically, to a method and device for implementing Ethernet ring network protection in a Time Sensitive Network (TSN) virtual bridge.

Background technique

TSN is a set of data link layer protocol specifications developed by the IEEE802.1 task group to build a more reliable, low-latency, and low-jitter Ethernet. TSN can provide microsecond-level deterministic services to ensure the real-time needs of various industries. Relying on 5G wireless access and the deterministic latency provided by TSN, 5G TSN technology can meet various indicators of deterministic communication in wireless network transmission, and is an important foundation for realizing the wirelessization of the industrial Internet and flexible manufacturing in the future.

As shown in Figure 1, TSN integrates the 5G system as a bridge in the TSN system, and the TSN network and the 5G network communicate with each other through the TSN converter function. The TSN converter includes the device side TSN converter (Device Side TSN Translator, DS-TT) and the network side TSN converter (Network Side TSN Translator, NW-TT); DS-TT is located on the terminal side, and NW-TT is located on the network side. Messages can enter the 5G bridge from DS-TT or NW-TT. The entire 5G network includes terminals, wireless, bearer networks, and core networks. In order to achieve the forwarding determinism of traffic passing through the 5G bridge as much as possible, the existing protocols (for example: 23501, 23502, 38413, 29244, 24519, 29513) have issued deterministic scheduling parameters at the nodes of the radio access network (RAN), DS-TT, and NW-TT that can distinguish TSN service flows.

The technical key to TSN's deterministic transmission is to reserve resources for TSN traffic according to the service cycle to ensure that when traffic arrives, there will be no random delays due to resource competition. The resource reservation here is reflected in the 5G bridge as the gating list on NW-TT/DS-TT and the pre-scheduling of wireless resources.

The Ethernet ring network is a widely used low-cost and highly reliable networking method. Its technical key points (refer to RFC3619/ITU-T803.2) are to configure the ring protection link (RPL) and RPL management node in the network. When the nodes and links in the ring network are normal, the RPL is in a blocked state to avoid loops; when a fault in the ring network causes the link to be interrupted, the RPL is unblocked to form a new network topology and forwarding table, complete the ring switching, and isolate the fault point.

As shown in Figure 2, 5g TSN bridges can also be deployed in Ethernet ring networks. When RPL is unblocked, it not only affects the forwarding table, but also affects the sharing of TSN traffic in each node. For example, after the link between C-D fails, the traffic between C-D needs to be adjusted to C-B-A-5g bridge-D path. At this time, the reserved TSN resources do not match the adjusted traffic, resulting in resource competition, thereby destroying TSN determinism.

Summary of the invention

The embodiments of the present disclosure provide a method and device for implementing Ethernet ring network protection in a TSN virtual bridge, so as to at least solve the problem that when a ring switch occurs in the Ethernet ring network, the service flow on each node will change and no longer meet the switching requirements. The TSN scheduling parameters before the change are changed, thus destroying the TSN determinism.

According to an embodiment of the present disclosure, a method for implementing Ethernet ring network protection in a TSN virtual bridge is provided, comprising: a TSN virtual bridge deployed in an Ethernet ring network receives a mapping table of fault identifiers and TSN scheduling parameters issued by a TSN control management unit; the TSN virtual bridge adjusts the TSN scheduling parameters in the mapping table to scheduling parameters of a corresponding network element in the TSN virtual bridge, and issues the adjusted mapping table to the corresponding network element; when the corresponding network element receives a status notification message triggered by a fault in the Ethernet ring network, the corresponding scheduling parameters are applied according to the fault identifier carried in the status notification message.

According to another embodiment of the present disclosure, a device for implementing Ethernet ring network protection in a time-sensitive network TSN virtual bridge is provided, which is applied to a TSN virtual bridge deployed in an Ethernet ring network, and the device includes: a receiving module, configured to receive a mapping table of fault identifiers and TSN scheduling parameters issued by a TSN control management unit; an adjustment module, configured to adjust the TSN scheduling parameters in the mapping table to scheduling parameters of a corresponding network element in the TSN virtual bridge, and to issue the adjusted mapping table to the corresponding network element; an application module, configured to apply the corresponding scheduling parameters according to the fault identifier carried in the status notification message when the network element receives a status notification message triggered by a fault in the Ethernet ring network.

According to another embodiment of the present disclosure, a computer-readable storage medium is provided, in which a computer program is stored, wherein the computer program is configured to execute the steps of any one of the above method embodiments when running.

According to another embodiment of the present disclosure, an electronic device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to execute the steps in any one of the above method embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of integrating a 5G system as a bridge in a TSN system according to the prior art;

FIG2 is a schematic diagram of a TSN bridge deployed in an Ethernet ring network according to the prior art;

3 is a flow chart of a method for implementing Ethernet ring network protection in a TSN virtual bridge according to an embodiment of the present disclosure;

4 is a flow chart of a method for implementing Ethernet ring network protection in a TSN virtual bridge according to another embodiment of the present disclosure;

FIG5 is a schematic diagram showing a mapping between a fault identifier and a TSN scheduling parameter according to an embodiment of the present disclosure;

6 is a schematic diagram of the structure of a device for implementing Ethernet ring network protection in a TSN virtual bridge according to an embodiment of the present disclosure;

7 is a schematic diagram of the structure of an apparatus for implementing Ethernet ring network protection in a TSN virtual bridge according to another embodiment of the present disclosure;

FIG. 8 is a schematic structural diagram of an electronic device according to the present disclosure.

Detailed ways

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings and in combination with the embodiments.

As described above, when a ring switch occurs in the Ethernet ring network, the service traffic on each node will change and no longer conform to the TSN scheduling parameters before the switch, thus destroying the TSN determinism.

To this end, the present disclosure provides a method for implementing Ethernet ring protection in a TSN virtual bridge to ensure that when the Ethernet ring is switched, data can be forwarded deterministically in the TSN bridge. FIG3 is a flow chart of a method according to an embodiment of the present disclosure. As shown in FIG3 , the process may include the following steps:

Step S302: The TSN virtual bridge deployed in the Ethernet ring network receives the fault identification and Mapping table of TSN scheduling parameters;

Step S304, the TSN virtual bridge adjusts the TSN scheduling parameters in the mapping table to the scheduling parameters of the corresponding network element in the TSN virtual bridge, and sends the adjusted mapping table to the corresponding network element;

Step S306: When the corresponding network element receives the status notification message triggered by the fault of the Ethernet ring network, the corresponding scheduling parameter is applied according to the fault identifier carried in the status notification message.

In this embodiment, the corresponding network elements in the TSN virtual bridge may include: user equipment UE, radio access network RAN, user plane function UPF, wherein the UE has a built-in device-side TSN converter DS-TT, and the UPF has a built-in network-side TSN converter NW-TT.

In this embodiment, the scheduling parameters of the corresponding network element may include: air interface scheduling parameters, DS-TT port scheduling parameters, and NW-TT port scheduling parameters.

In an exemplary embodiment, before step S302, it may also include: a TSN control management unit determines the number of entries in the mapping table according to the TSN ring protection capability of the corresponding network element; the TSN control management unit compiles the mapping table and sends it to the TSN virtual bridge according to the traffic characteristics after a failure of each node/port in the Ethernet ring network, as well as the fault identification and protection priority assigned to each node/port.

In an exemplary embodiment, before the TSN control management unit arranges the mapping table, it may also include: the AF in the TSN virtual bridge obtains the TSN loop protection capability of the corresponding network element in the TSN virtual bridge, and reports it to the TSN control management unit.

In an exemplary embodiment, the AF obtains the TSN loop protection capability of the corresponding network element in the TSN virtual bridge, including: the AF receives the TSN loop protection capability reported by the corresponding network element supporting TSN loop protection in the TSN virtual bridge along the control plane signaling; the AF obtains the lower limit of the TSN loop protection capability of the corresponding network element and reports it to the TSN control management unit.

In an exemplary embodiment, before step S306, it may also include: the node in the Ethernet ring network sends the status notification message along the ring after detecting a fault; and the RPL management node uncloses the loop protection link to form a new message path after receiving the status notification message.

In an exemplary embodiment, the method may further include: when the corresponding network element in the TSN virtual bridge receives the fault recovery notification message triggered by the Ethernet ring network, the network element restores the current scheduling parameters to the scheduling parameters before the Ethernet ring network failure or maintains the current scheduling parameters.

In the above-mentioned embodiment of the present disclosure, by pre-issuing the mapping table of fault identification and TSN scheduling parameters to the TSN virtual bridge, when a fault occurs in the Ethernet ring network and switching is performed, each corresponding node in the TSN virtual bridge can apply the corresponding scheduling parameters according to the fault identification to adapt to the new Ethernet ring, thereby ensuring the determinism of TSN.

In order to more clearly describe the technical solution provided by the present disclosure, a description will be given below in conjunction with a specific scenario embodiment.

This embodiment also provides a method for implementing Ethernet ring network protection in a TSN virtual bridge to ensure that data can be forwarded deterministically in the TSN bridge when a switch occurs in the Ethernet ring network. As shown in FIG4 , the method may include the following process steps:

Step 1: If the AF has not obtained the TSN capability of the UPF selected in the current TSN session, it obtains the TSN capability from the UPF along the control plane signaling path; if the UPF supports the TSN loop protection capability, it carries this capability and reports it to the AF along the control plane signaling.

In this step, AF needs to obtain the TSN capability of UPF to determine whether TSN loop protection capability and specific parameters are supported.

In an exemplary embodiment, the AF may transmit 24519 through the AF-PCF-SMF-UPF transmission path (existing protocol flow). The GetCapability command defined in the protocol is encapsulated in TSC and sent to UPF. If UPF supports loop protection capability, it will encapsulate the parameter IE (such as 8001H) extended for this purpose in TSC and bring it to AF through the UPF-SMF-PCF-AF path. AF finds that UPF supports this capability, and through the AF-PCF-SMF-UPF transmission path (existing protocol process), it encapsulates the read parameter command defined in the 24519 protocol (parameter IE is 8001H) in TSC and sends it to UPF to read the specific value of this parameter. UPF fills the specific value of this parameter IE (such as 8001H) into the Ethernet port status response defined in the 24519 protocol, and brings it to AF through the UPF-SMF-PCF-AF path.

Step 2: If the UE and the RAN to which the UE accesses support TSN loop protection, this capability is carried when the TSN PDU session is established and reported to the AF along the control plane signaling.

In an exemplary embodiment, the UE adds a loop protection capability IE parameter in the (ETHERNET PORT MANAGEMENT CAPABILITY) command in the PMIC of the PDU session establishment request at the N1 port; the RAN carries its own loop protection capability (adds a new IE) in the PDU Session Resource Setup at the N2 port; after receiving the SMF, if both the UE and the RAN support loop protection, it is brought to the AF through the RAN-AMF-SMF-PCF-AF path and the RAN capability is recorded; otherwise, the SMF deletes this parameter in the PMIC reported by the UE.

AF discovers that UE supports this capability, and encapsulates the read parameter command defined in the 24519 protocol (assuming the extended parameter IE is 8001H) in the PMIC through the AF-PCF-SMF-RAN-UE transmission path (existing protocol process), and sends it to the UE through the PDU session modification command to read the specific value of this parameter.

The UE fills the specific value of this parameter IE (such as 8001H) into the Ethernet port status response defined in the 24519 protocol, encapsulates it in the PMIC, and sends it to the RAN-SMF through the PDU session modification request; the SMF calculates the smaller value of the UE capability and the saved RAN capability, updates this IE, and brings it to the AF through the SMF-PCF-AF.

Step 3: If the AF determines that the UE, RAN and UPF carrying the TSN session all support TSN loop protection, the TSN loop protection capabilities of the three are reported to the CNC. The AF can report the lower limit of the capabilities of the three to the CNC.

In an exemplary embodiment, the AF reports the mapping list capability of the port to the CNC in a netconf message.

Step 4: CNC determines that this TSN port pair is located in a certain Ethernet ring network based on the reported DS-TT port identifier, NW-TT port identifier, and the service flow characteristics issued by CUC; determines the maximum number of [fault identifier, TSN scheduling parameter] mapping list entries that this TSN port pair can support based on the reported TSN bridge loop protection capability; and determines the mapping list based on the pre-configured Ethernet ring fault point protection priority.

In an exemplary embodiment, the CNC can pre-configure the node and port numbers of the TSN ring network as fault point numbers according to the numbering method agreed in G.8032; pre-arrange new TSN scheduling parameters when each port fails according to traffic characteristics and loop SPL positions to form a [fault point, TSN scheduling parameter] mapping list; sort the aforementioned list from high to low according to the possibility of failure; and select a high-priority list within the capacity range as the mapping list for port scheduling based on the reported list processing number.

In step 5, CNC sends the above mapping list to the 5G TSN virtual bridge along the control plane signaling; the SMF in the virtual bridge adjusts the parameters in the mapping list to air interface scheduling parameters, DS-TT port scheduling parameters, and NW-TT port scheduling parameters, and sends them to RAN, UE, and UPF respectively.

In an exemplary embodiment, for example, the SMF maps a set of parameters used by each network element for each item in the mapping table, as shown in FIG5 . The mapped air interface scheduling parameters are the QoS Flow List in protocol 38413 and are sent to the RAN for use; the Qos Rule/Qos Flow Description List in protocol 24501 is used by the UE; the port scheduling parameters PMIC in protocol 24519 are mapped for use by DS-TT and NW-TT; and the PDR/QER List in protocol 29244 is mapped for use by the UPF.

Step 6: The node in the Ethernet ring network detects a direct link failure and sends a status notification message along the ring network; after receiving the notification, the SPL management/adjacent node unblocks the SPL to form a new message path; after receiving the notification message, the RAN/UE/UPF applies the corresponding air interface scheduling parameters, DS-TT port scheduling parameters, and NW-TT port scheduling parameters according to the fault identifier in the notification message to adapt to the new message path and ensure deterministic forwarding of messages.

In an exemplary embodiment, a node in an Ethernet ring network can listen to the SF (signal failure) message in G.8032, and according to the node ID and port ID in the message, search the mapping table sent down and apply the corresponding TSN scheduling rules and forwarding strategies.

In an exemplary embodiment, after step 6, a step 7 (not shown in the figure) may be further included.

Step 7: After the link failure is restored, the node sends a status notification carrying the link recovery; the SPL management node and the 5G bridge can be restored to the normal state and scheduling strategy according to the strategy, or the scheduling strategy at the time of the failure can be maintained.

It should be noted that in the above embodiments of the present disclosure, in addition to the above parameters, the scheduling parameters for loop switching can also be extended with additional private parameters. In addition to being issued in advance, the scheduling parameter list for loop switching can also be subscribed to the SF signal to the NW-TT/DS-TT. When a loop switch occurs, the NW-TT/DS-TT reports the fault point number to the AF/CNC, and the CNC updates it to the new TSN scheduling parameter according to the fault point number.

Through the description of the above implementation methods, those skilled in the art can clearly understand that the method according to the above embodiment can be implemented by means of software plus a necessary general hardware platform, and of course can also be implemented by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present disclosure, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM/RAM, a disk, or an optical disk), and includes a number of instructions for enabling a terminal device (computer, server, or network device, etc.) to execute the methods described in each embodiment of the present disclosure.

In this embodiment, a device for implementing Ethernet ring protection in a TSN virtual bridge is also provided, which is used to implement the above-mentioned embodiments and exemplary implementations, and will not be repeated here. As used below, the term "module" can implement a combination of software and/or hardware of a predetermined function. Although the device described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.

FIG6 is a structural block diagram of a device for implementing Ethernet ring network protection in a TSN virtual bridge according to an embodiment of the present disclosure, and the device can be applied to a TSN virtual bridge deployed in an Ethernet ring network. As shown in FIG6 , the device includes:

A receiving module 10 is configured to receive a mapping table of fault identification and TSN scheduling parameters issued by a TSN control management unit;

An adjustment module 20 is configured to adjust the TSN scheduling parameters in the mapping table to the scheduling parameters of the corresponding network element in the TSN virtual bridge, and send the adjusted mapping table to the corresponding network element;

The application module 30 is configured to apply corresponding scheduling parameters according to the fault identifier carried in the status notification message when the corresponding network element receives a status notification message triggered by a fault in the Ethernet ring network.

In an exemplary embodiment, the corresponding network elements in the TSN virtual bridge include: user equipment UE, radio access network RAN, and user plane function UPF, wherein the UE has a built-in device-side TSN converter DS-TT, and the UPF has a built-in network-side TSN converter NW-TT.

In an exemplary embodiment, the scheduling parameters of the corresponding network element include: air interface scheduling parameters, DS-TT port scheduling parameters, and NW-TT port scheduling parameters.

FIG. 7 is a structural block diagram of a device for implementing Ethernet ring network protection in a TSN virtual bridge according to another embodiment of the present disclosure. As shown in FIG. 7 , the device includes, in addition to all the modules shown in FIG. 6 , further includes:

The recovery module 40 is configured to restore the current scheduling parameters of the corresponding network element to the scheduling parameters before the Ethernet ring network failure or maintain the current scheduling parameters when the corresponding network element receives the fault recovery notification message triggered by the Ethernet ring network.

It should be noted that the above modules can be implemented by software or hardware. For the latter, it can be implemented in the following ways, but not limited to: the above modules are all located in the same processor; or the above modules are located in different processors in any combination.

An embodiment of the present disclosure further provides a computer-readable storage medium, in which a computer program is stored, wherein the computer program is configured to execute the steps of any of the above method embodiments when running.

In an exemplary embodiment, the above-mentioned computer-readable storage medium may include, but is not limited to: a USB flash drive, a read-only memory (ROM), a random access memory (RAM), a mobile hard disk, a magnetic disk or an optical disk, and other media that can store computer programs.

An embodiment of the present disclosure further provides an electronic device, including a memory 50 and a processor 60, wherein the memory 50 stores a computer program, and the processor 60 is configured to run the computer program to execute the steps in any one of the above method embodiments.

In an exemplary embodiment, the electronic device may further include a transmission device and an input/output device, wherein the transmission device is connected to the processor, and the input/output device is connected to the processor.

For specific examples in this embodiment, reference may be made to the examples described in the above embodiments and exemplary implementation modes, and this embodiment will not be described in detail herein.

Obviously, those skilled in the art should understand that the above-mentioned modules or steps of the present disclosure can be implemented by a general-purpose computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order than here, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. In this way, the present disclosure is not limited to any specific combination of hardware and software.

The above description is only an exemplary embodiment of the present disclosure and is not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the principles of the present disclosure shall be included in the protection scope of the present disclosure.

Claims (14)

A method for implementing Ethernet ring network protection in a time-sensitive network TSN virtual bridge, comprising: The TSN virtual bridge deployed in the Ethernet ring network receives the mapping table of fault identification and TSN scheduling parameters issued by the TSN control management unit; The TSN virtual bridge adjusts the TSN scheduling parameters in the mapping table to the scheduling parameters of the corresponding network element in the TSN virtual bridge, and sends the adjusted mapping table to the corresponding network element; When the corresponding network element receives the status notification message triggered by the fault of the Ethernet ring network, the corresponding scheduling parameter is applied according to the fault identifier carried in the status notification message. According to the method of claim 1, the corresponding network elements in the TSN virtual bridge include: user equipment UE, radio access network RAN, user plane function UPF, wherein the UE has a built-in device-side TSN converter DS-TT, and the UPF has a built-in network-side TSN converter NW-TT. The method according to claim 2, wherein the scheduling parameters of the corresponding network element include: air interface scheduling parameters, DS-TT port scheduling parameters, and NW-TT port scheduling parameters. The method according to claim 1, wherein, before the TSN virtual bridge receives the mapping table sent by the TSN control management unit, it also includes: The TSN control management unit determines the number of entries in the mapping table according to the TSN loop protection capability of the corresponding network element; The TSN control management unit compiles the mapping table according to the traffic characteristics after each node/port in the Ethernet ring network fails, as well as the fault identification and protection priority assigned to each node/port, and sends it to the TSN virtual bridge. The method according to claim 4, wherein, before the TSN control management unit arranges the mapping table, it also includes: The application function AF in the TSN virtual bridge obtains the TSN loop protection capability of the corresponding network element in the TSN virtual bridge and reports it to the TSN control management unit. The method according to claim 5, wherein the AF obtains the TSN loop protection capability of the corresponding network element in the TSN virtual bridge comprises: The AF receives the TSN loop protection capability reported by the corresponding network element supporting TSN loop protection in the TSN virtual bridge along the control plane signaling; The AF obtains the lower limit of the TSN loop protection capability of the corresponding network element and reports it to the TSN control management unit. The method according to claim 1, wherein, before the TSN virtual bridge receives the status notification message triggered by the failure of the Ethernet ring network, it also includes: After detecting a fault, the node in the Ethernet ring network sends the status notification message along the ring; After receiving the status notification message, the loop protection link RPL management node uncloses the loop protection link to form a new message path. The method according to claim 1, further comprising: When the corresponding network element in the TSN virtual bridge receives the fault recovery notification message triggered by the Ethernet ring network, the network element restores the current scheduling parameters to the scheduling parameters before the Ethernet ring network failure or maintains the current scheduling parameters. A device for implementing Ethernet ring network protection in a time sensitive network TSN virtual bridge, applied to a TSN virtual bridge deployed in an Ethernet ring network, comprising: A receiving module, configured to receive a mapping table of fault identification and TSN scheduling parameters issued by a TSN control management unit; An adjustment module, configured to adjust the TSN scheduling parameters in the mapping table to the scheduling parameters of the corresponding network element in the TSN virtual bridge, and send the adjusted mapping table to the corresponding network element; The application module is configured to apply corresponding scheduling parameters according to the fault identifier carried in the status notification message when the network element receives a status notification message triggered by a fault in the Ethernet ring network. The device according to claim 9, wherein the corresponding network elements in the TSN virtual bridge include: user equipment UE, radio access network RAN, user plane function UPF, wherein the UE has a built-in device-side TSN converter DS-TT, and the UPF has a built-in network-side TSN converter NW-TT. The device according to claim 10, wherein the scheduling parameters of the corresponding network element include: air interface scheduling parameters, DS-TT port scheduling parameters, and NW-TT port scheduling parameters. The device according to claim 9, further comprising: The recovery module is configured to restore the current scheduling parameters of the corresponding network element to the scheduling parameters before the Ethernet ring network failure or maintain the current scheduling parameters when the corresponding network element receives the fault recovery notification message triggered by the Ethernet ring network. A computer-readable storage medium having a computer program stored therein, wherein the computer program, when executed by a processor, implements the steps of the method described in any one of claims 1 to 8. An electronic device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method described in any one of claims 1 to 8 when executing the computer program.