CN113839862A

CN113839862A - Method, system, terminal and storage medium for synchronizing ARP information between MCLAG neighbors

Info

Publication number: CN113839862A
Application number: CN202111089267.9A
Authority: CN
Inventors: 董建军; 郭巍松
Original assignee: Suzhou Inspur Intelligent Technology Co Ltd
Current assignee: Suzhou Inspur Intelligent Technology Co Ltd
Priority date: 2021-09-16
Filing date: 2021-09-16
Publication date: 2021-12-24
Anticipated expiration: 2041-09-16
Also published as: CN113839862B

Abstract

The invention provides a method, a system, a terminal and a storage medium for synchronizing ARP information between MCLAG neighbors, wherein the method comprises the following steps: monitoring a new address resolution protocol table entry and an address resolution protocol message of a switch kernel, and extracting address resolution protocol table entry information from the address resolution protocol message; and synchronizing the new address resolution protocol table entry and the address resolution protocol table entry information to the neighbor node of the target node, wherein the target node and the neighbor node belong to the same cross-device link aggregation group. The invention can effectively prevent the aging of the ARP information of the cross-equipment link aggregation group node or the switch, and can realize little or no packet loss when the link is switched, thereby bringing better use experience to users.

Description

Method, system, terminal and storage medium for synchronizing ARP information between MCLAG neighbors

Technical Field

The invention relates to the technical field of data communication, in particular to a method, a system, a terminal and a storage medium for synchronizing ARP information between MCLAG neighbors.

Background

An LACP (Link Aggregation Control Protocol) based on the ieee802.3ad standard is a Protocol for realizing dynamic Link Aggregation. The LACP protocol exchanges information with the opposite end through LACPDUs (link convergence control protocol data units). After the LACP protocol of a certain port is enabled, the port notifies the opposite end of the own system priority, system MAC address, port priority, port number and operation Key by sending LACPDU. After receiving the information, the opposite terminal compares the information with the information stored in other ports to select the port capable of converging, so that the two sides can reach the agreement of the port joining or exiting a certain dynamic convergence group. The use of link aggregation techniques increases the bandwidth of the logical link by a factor of approximately (n-1), where n is the number of aggregated ways. In addition, after aggregation, the reliability is greatly improved, because only one of the n links can work normally, the link can work. In addition, link aggregation may enable load balancing. Because, two switches (or other network devices) connected together by link aggregation can reasonably distribute data on the devices connected by aggregation through internal control, thereby realizing load sharing. For example, the LACP runs between devices A, B, aggregating three ports. The three links can operate in active and standby modes and can also operate in load balance mode. When a certain link fails, data forwarding is not affected. The LACP realizes link backup, but cannot aggregate across devices, and does not solve the problem of single point failure of devices. Data forwarding may still be affected by the failure of any one of devices A, B.

MCLAG (Multi Chassis Link Aggregation Group) is a mechanism for implementing cross-device Link Aggregation, and provides device-level redundancy by virtualizing two physical devices into a single logical device. When one device fails, the flow can be quickly switched to the other device, and zero packet loss or as few packet loss as possible can be realized. For example, device CE1 aggregates across devices with device PE1, PE 2. In view of CE1, PE1 and PE2 are the same device. When PE1 or PE2 has a device failure, CE1 can quickly switch traffic to another device so that data forwarding is not affected. Generally, the shorter the packet loss time, the better the device rebot is required to be. In the current implementation of MCLAG of the sonoc, when rebot operation is performed on a device, packet loss occurs in about 200 milliseconds during a down device, and a relatively large optimization space exists.

In order to achieve the purpose that when the PE1 or PE2 has an equipment failure, the CE1 can quickly switch the traffic to another device and reduce the data packet loss as little as possible, it is necessary to synchronize forwarding related entries, such as a MAC address table, an ARP table, and the like, between the two devices in advance. Thus, when one device fails, the other device prepares the needed table entry in advance, and the flow forwarding is basically not influenced. The existing ARP table often has the problems of untimely synchronization and aging of the ARP table, and the MCLAG redundancy performance is seriously influenced.

Disclosure of Invention

In view of the above-mentioned deficiencies of the prior art, the present invention provides a method, a system, a terminal and a storage medium for synchronizing ARP information between MCLAG neighbors, so as to solve the above-mentioned technical problems.

In a first aspect, the present invention provides a method for synchronizing ARP information between MCLAG neighbors, including:

monitoring a new address resolution protocol table entry and an address resolution protocol message of a switch kernel, and extracting address resolution protocol table entry information from the address resolution protocol message;

and synchronizing the new address resolution protocol table entry and the address resolution protocol table entry information to the neighbor node of the target node, wherein the target node and the neighbor node belong to the same cross-device link aggregation group.

Further, monitoring a new address resolution protocol table entry and an address resolution protocol message of the switch kernel, and extracting address resolution protocol table entry information from the address resolution protocol message, including:

monitoring an address resolution protocol table item learned by a switch kernel through a communication protection mechanism of a switch, and synchronizing the new address resolution protocol table item to a neighbor node if the address resolution protocol table item is the new address resolution protocol table item;

extracting and extracting address resolution protocol table entry information from an address resolution protocol message received by a switch, and synchronously transmitting the address resolution protocol table entry information to a neighbor node while transmitting the address resolution protocol message to a target node.

Further, extracting the arp table information from the arp message received by the switch, and sending the arp table information to the neighboring node simultaneously when sending the arp message to the target node, the method includes:

the neighbor node judges whether the same address resolution protocol table item exists locally according to the information content of the address resolution protocol table item:

if yes, discarding the address resolution protocol table entry information;

if not, the corresponding address resolution protocol table entry is stored to the local according to the address resolution protocol table entry information, and response information of the address resolution protocol table entry message is returned to the switch.

Further, synchronizing the new address resolution protocol table entry and the address resolution protocol table entry information to the neighbor node of the target node, where the target node and the neighbor node belong to the same cross-device link aggregation group, including:

the information synchronization period is set to be 30min, and data synchronization is executed every 30 min.

In a second aspect, the present invention provides a system for synchronizing ARP information between MCLAG neighbors, including:

the information monitoring unit is used for monitoring a new address resolution protocol table entry and an address resolution protocol message of the switch kernel and extracting the address resolution protocol table entry information from the address resolution protocol message;

and the information synchronization unit is used for synchronizing the new address resolution protocol table entry and the address resolution protocol table entry information to the neighbor node of the target node, wherein the target node and the neighbor node belong to the same cross-device link aggregation group.

Further, the information monitoring unit is configured to:

if yes, discarding the address resolution protocol table entry information;

Further, the information synchronization unit is configured to:

In a third aspect, a terminal is provided, including:

a processor, a memory, wherein,

the memory is used for storing a computer program which,

the processor is used for calling and running the computer program from the memory so as to make the terminal execute the method of the terminal.

In a fourth aspect, a computer storage medium is provided having stored therein instructions that, when executed on a computer, cause the computer to perform the method of the above aspects.

The beneficial effect of the invention is that,

the method, the system, the terminal and the storage medium for synchronizing the ARP information between MCLAG neighbors provided by the invention are characterized in that a new address resolution protocol table entry and an address resolution protocol message of a switch kernel are monitored, the address resolution protocol table entry information is extracted from the address resolution protocol message, and then the new address resolution protocol table entry and the address resolution protocol table entry information are synchronized to neighbor nodes of a target node of the same cross-device link aggregation group. The invention can effectively prevent the aging of the ARP information of the cross-equipment link aggregation group node or the switch, and can realize little or no packet loss when the link is switched, thereby bringing better use experience to users.

In addition, the invention has reliable design principle, simple structure and very wide application prospect.

Drawings

In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.

FIG. 1 is a schematic flow diagram of a method of one embodiment of the invention.

Fig. 2 is a schematic diagram of an MCLAG architecture of a method according to an embodiment of the present invention.

FIG. 3 is a schematic block diagram of a system of one embodiment of the present invention.

Fig. 4 is a schematic structural diagram of a terminal according to an embodiment of the present invention.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The following explains key terms appearing in the present invention.

A Switch means a "Switch" is a network device used for electrical (optical) signal forwarding. It may provide an exclusive electrical signal path for any two network nodes accessing the switch. The most common switch is an ethernet switch. Other common are telephone voice switches, fiber switches, and the like. The exchange is a general name of the technology of sending the information to be transmitted to the corresponding route meeting the requirements by a method of manual or automatic completion by equipment according to the requirements of transmitting the information at two communication ends. The switches can be divided into wide area network switches and local area network switches according to the working positions. The wide area switch is a device for performing information exchange function in a communication system, and is applied to a data link layer. The switch has a plurality of ports, each port has a bridging function and can be connected with a local area network or a high-performance server or a workstation. In practice, switches are sometimes referred to as multi-port bridges. A network switch is a device for expanding a network, and can provide more connection ports for a sub-network so as to connect more computers. With the development of the communication industry and the promotion of informatization of national economy, the network switch market is in a steady rising situation. The method has the characteristics of high cost performance, high flexibility, relative simplicity, easy realization and the like. Ethernet technology has become one of the most important lan networking technologies today, and network switches have become the most popular switches. Switch is the english name of Switch, and this product is from the upgrading of former concentrator, and does not have very big difference with the concentrator in the outward appearance. This technology is a switch technology, because both ends of communication need to transmit information, and the information to be transmitted is sent to the corresponding router meeting the required standard by equipment or manpower. Broadly, a device implemented for information exchange functions in a communication system is a switch. The address Resolution protocol (arp) is a TCP/IP protocol for acquiring a physical address according to an IP address. When the host sends information, the ARP request containing the target IP address is broadcasted to all the hosts on the local area network, and the return message is received, so that the physical address of the target is determined; after receiving the return message, the IP address and the physical address are stored in the local ARP cache and are kept for a certain time, and the ARP cache is directly inquired when the next request is made so as to save resources. The address resolution protocol is established on the basis that all hosts trust each other in the network, the hosts on the local area network can independently send ARP response messages, and other hosts can not detect the authenticity of the messages and can record the messages into the ARP cache of the local hosts when receiving the response messages; therefore, an attacker can send a false ARP response message to a certain host, so that the sent information cannot reach an expected host or reach a wrong host, and ARP spoofing is formed. The ARP command may be used to query the correspondence between IP addresses and MAC addresses in the local ARP cache, add or delete static correspondence, and the like. The related protocols include RARP and proxy ARP. NDP is used in place of the address resolution protocol in IPv 6. The working process is as follows: the IP address of the host A is 192.168.1.1, and the MAC address is 0A-11-22-33-44-01; the IP address of the host B is 192.168.1.2, and the MAC address is 0A-11-22-33-44-02; when host a is to communicate with host B, the address resolution protocol may resolve the IP address of host B (192.168.1.2) to the MAC address of host B, with the following workflow: step 1: from the routing table contents on host a, IP determines that the forwarding IP address for accessing host B is 192.168.1.2. The a-host then checks its own local ARP cache for the matching MAC address of host B. Step 2: if host a does not find a mapping in the ARP cache, it will query the hardware address of 192.168.1.2, broadcasting an ARP request frame to all hosts on the local network. Both the IP address and the MAC address of source host a are included in the ARP request. Each host on the local network receives the ARP request and checks if it matches its own IP address. If the host finds that the requested IP address does not match its own IP address, it will discard the ARP request. And 3, step 3: and the host B determines that the IP address in the ARP request is matched with the IP address of the host B, and then the IP address and the MAC address of the host A are mapped and added into a local ARP cache. And 4, step 4: host B sends an ARP reply message containing its MAC address directly back to host a. And 5, step 5: when host a receives the ARP reply message from host B, the ARP cache is updated with the IP and MAC address mapping of host B. The local cache has a lifetime, and after the lifetime is over, the above process is repeated again. Once the MAC address of host B is determined, host a can send an IP communication to host B.

FIG. 1 is a schematic flow diagram of a method of one embodiment of the invention. The execution subject in fig. 1 may be a system for synchronizing ARP information between MCLAG neighbors.

As shown in fig. 1, the method includes:

step 110, monitoring a new address resolution protocol table entry and an address resolution protocol message of a switch kernel, and extracting address resolution protocol table entry information from the address resolution protocol message;

step 120, synchronizing the new address resolution protocol table entry and the address resolution protocol table entry information to the neighbor node of the target node, wherein the target node and the neighbor node belong to the same cross-device link aggregation group.

In order to facilitate understanding of the present invention, the method for synchronizing ARP information between MCLAG neighbors provided in the present invention is further described below by using the principle of the method for synchronizing ARP information between MCLAG neighbors of the present invention in combination with the process of synchronizing ARP information in the embodiments.

Specifically, referring to fig. 2, the method for synchronizing ARP information between MCLAG neighbors includes:

s1, monitoring the new address resolution protocol table item and the address resolution protocol message of the switch kernel, and extracting the address resolution protocol table item information from the address resolution protocol message.

The device CE1 aggregates with the devices PE1, PE2 across devices. In view of CE1, PE1 and PE2 are the same device. When PE1 or PE2 has a device failure, CE1 can quickly switch traffic to another device so that data forwarding is not affected. In order to achieve the purpose that when the PE1 or PE2 has an equipment failure, the CE1 can quickly switch the traffic to another equipment and reduce the data packet loss as little as possible, it is necessary to synchronize forwarding related entries, such as a MAC address table and an ARP table, between the two equipments in advance. Thus, when one device fails, the other device prepares the needed table entry in advance, and the flow forwarding is basically not influenced.

The switch can monitor the ARP table items learned by the kernel through a netlink mechanism. When the kernel learns a new ARP table entry, the kernel informs the MCLAG module through the netlink. After MCLAG receives it, it can synchronize to the neighbors over the TCP connection. The switch receives the ARP information synchronized from the neighbor and can send the linux kernel of the switch in a dynamic table entry mode or a static table entry mode. When the kernel is issued in a dynamic table entry manner, there is a problem of table entry aging. In the kernel, the ARP entry will age if there is no hit by default for more than 30 minutes. Before aging, the kernel sends an ARP request and then waits for the corresponding ARP reply. In the exchanger, the flow forwarding is responsible for hardware, the flow cannot be sent to the CPU, the ARP table entry basically cannot be hit, and as a result, the ARP table entry in the kernel can be aged once every 30 minutes. There is also a problem when to age when issuing cores with static entries. The static ARP list item can not be aged in the kernel, and even if the terminal corresponding to the ARP is separated, the ARP can not be aged. This is obviously also not a desirable result. Comprehensively considering, the switch receives the ARP information synchronized from the neighbor and issues the linux kernel of the switch in a dynamic table entry mode. Before the ARP table entry is aged, the kernel sends an ARP request and then waits for a corresponding ARP reply. In general, if the terminal corresponding to the ARP is still active, the switch will receive the corresponding ARP reply, so as to update the ARP entry stored in itself.

However, in MCLAG environment, when a PE sends out an ARP request, the PE may not receive the corresponding ARP reply even though the ARP corresponding terminal is still active. For example, when PE1 requests ARP of CE1, CE1 may send ARP reply to PE2 because CE1 considers PE1 and PE2 to be the same switch, resulting in PE1 not receiving the corresponding ARP reply. If PE2 kernel has the ARP entry at this time, MCLAG will not receive notification of learning new ARP entry, and therefore PE1 will not be notified, with the result that the ARP entry on PE1 is aged.

For this reason, ARP information assimilation needs to be performed from two dimensions. One aspect is to monitor a new address resolution protocol table entry of the switch core, that is, after the switch forwards the ARP information to the target node, if the target node does not have the same address resolution protocol table entry, the ARP information is stored and a signal is returned to the switch, and the switch checks the ARP information and learns to obtain the new address resolution protocol table entry. The method comprises the steps of monitoring an ARP table entry learned by a switch kernel through a communication protection mechanism of a switch, and synchronizing a new ARP table entry to a neighbor node if the ARP table entry is the new ARP table entry.

Meanwhile, aiming at the condition that the target node is selected by mistake, the ARP message of the inner core of the switch is monitored, and the ARP table entry information is extracted from the ARP message. Specifically, the address resolution protocol table entry information is extracted from the address resolution protocol message received by the switch, and the address resolution protocol table entry information is synchronously sent to the neighbor node while the address resolution protocol message is sent to the target node.

S2, synchronizing the new address resolution protocol table entry and the address resolution protocol table entry information to the neighbor nodes of the target node, wherein the target node and the neighbor nodes belong to the same cross-device link aggregation group.

And synchronizing the new address resolution protocol table entry and the address resolution protocol table entry information in the step S1 to the neighbor node of the target node. The neighbor node judges whether the same address resolution protocol table item exists locally according to the information content of the address resolution protocol table item: if yes, discarding the address resolution protocol table entry information; if not, the corresponding address resolution protocol table entry is stored to the local according to the address resolution protocol table entry information, and response information of the address resolution protocol table entry message is returned to the switch.

The switch monitors the ARP table entry learned by the Linux kernel through the netlink, and simultaneously monitors the ARP message received by the switch, extracts the ARP table entry information from the message, and synchronizes the ARP table entry information to the neighbor. For example, when PE1 requests ARP of CE1, since CE1 considers PE1 and PE2 to be the same switch, if CE1 sends ARP reply to PE2, PE2, upon receiving ARP reply, the MCLAG module processes the ARP reply, synchronizes the ARP entry to PE1, and updates the ARP entry of PE 1.

Through the mechanism, the ARP entries stored by PE1 and PE2 can not be aged.

In order to prevent the ARP synchronization information between PE1 and PE2 from being too frequent, resulting in busy CPU and high bandwidth occupation, the time for synchronizing the ARP entry to the neighbor may be recorded. Within 30 minutes, the related ARP list items are synchronized to the neighbor once, so that the ARP list items can be ensured not to be aged under the condition of reducing network communication quantity and CPU occupation as much as possible.

As shown in fig. 3, the system 300 includes:

an information monitoring unit 310, configured to monitor a new address resolution protocol entry and an address resolution protocol packet of a switch core, and extract address resolution protocol entry information from the address resolution protocol packet;

an information synchronization unit 320, configured to synchronize the new address resolution protocol entry and the address resolution protocol entry information to a neighbor node of the target node, where the target node and the neighbor node belong to the same cross-device link aggregation group.

Optionally, as an embodiment of the present invention, the information monitoring unit is configured to:

Optionally, as an embodiment of the present invention, extracting and extracting address resolution protocol table entry information from an address resolution protocol message received by a switch, and sending the address resolution protocol table entry information to a target node and simultaneously sending the address resolution protocol table entry information to a neighbor node synchronously includes:

if yes, discarding the address resolution protocol table entry information;

Optionally, as an embodiment of the present invention, the information synchronization unit is configured to:

Fig. 4 is a schematic structural diagram of a terminal 400 according to an embodiment of the present invention, where the terminal 400 may be configured to execute the method for synchronizing ARP information between MCLAG neighbors according to the embodiment of the present invention.

Among them, the terminal 400 may include: a processor 410, a memory 420, and a communication unit 430. The components communicate via one or more buses, and those skilled in the art will appreciate that the architecture of the servers shown in the figures is not intended to be limiting, and may be a bus architecture, a star architecture, a combination of more or less components than those shown, or a different arrangement of components.

The memory 420 may be used for storing instructions executed by the processor 410, and the memory 420 may be implemented by any type of volatile or non-volatile storage terminal or combination thereof, such as Static Random Access Memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic disk or optical disk. The executable instructions in memory 420, when executed by processor 410, enable terminal 400 to perform some or all of the steps in the method embodiments described below.

The processor 410 is a control center of the storage terminal, connects various parts of the entire electronic terminal using various interfaces and lines, and performs various functions of the electronic terminal and/or processes data by operating or executing software programs and/or modules stored in the memory 420 and calling data stored in the memory. The processor may be composed of an Integrated Circuit (IC), for example, a single packaged IC, or a plurality of packaged ICs connected with the same or different functions. For example, the processor 410 may include only a Central Processing Unit (CPU). In the embodiment of the present invention, the CPU may be a single operation core, or may include multiple operation cores.

A communication unit 430, configured to establish a communication channel so that the storage terminal can communicate with other terminals. And receiving user data sent by other terminals or sending the user data to other terminals.

The present invention also provides a computer storage medium, wherein the computer storage medium may store a program, and the program may include some or all of the steps in the embodiments provided by the present invention when executed. The storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM) or a Random Access Memory (RAM).

Therefore, the invention monitors the new address resolution protocol table entry and the address resolution protocol message of the switch kernel, extracts the address resolution protocol table entry information from the address resolution protocol message, and then synchronizes the new address resolution protocol table entry and the address resolution protocol table entry information to the neighbor node of the target node of the same cross-device link aggregation group. The invention can effectively prevent the aging of the ARP information of the cross-device link aggregation group node or the switch, can achieve little or no packet loss when the link switching occurs, and brings better use experience to users.

Those skilled in the art will readily appreciate that the techniques of the embodiments of the present invention may be implemented as software plus a required general purpose hardware platform. Based on such understanding, the technical solutions in the embodiments of the present invention may be embodied in the form of a software product, where the computer software product is stored in a storage medium, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and the like, and the storage medium can store program codes, and includes instructions for enabling a computer terminal (which may be a personal computer, a server, or a second terminal, a network terminal, and the like) to perform all or part of the steps of the method in the embodiments of the present invention.

The same and similar parts in the various embodiments in this specification may be referred to each other. Especially, for the terminal embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant points can be referred to the description in the method embodiment.

In the embodiments provided in the present invention, it should be understood that the disclosed system and method can be implemented in other ways. For example, the above-described system embodiments are merely illustrative, and for example, the division of the units is only one logical functional division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, systems or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit.

Although the present invention has been described in detail by referring to the drawings in connection with the preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made on the embodiments of the present invention by those skilled in the art without departing from the spirit and scope of the present invention, and these modifications or substitutions are within the scope of the present invention/any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for synchronizing ARP information between MCLAG neighbors, comprising:

2. The method of claim 1, wherein monitoring new ARP (Address resolution protocol) table entries and ARP (Address resolution protocol) messages of a switch core and extracting ARP table entry information from the ARP messages comprises:

3. The method of claim 2, wherein extracting ARP table entry information from ARP messages received by the switch and sending the ARP table entry information to the target node simultaneously with the ARP messages to the neighboring nodes comprises:

if yes, discarding the address resolution protocol table entry information;

4. The method of claim 1, wherein synchronizing both new ARP table entries and ARP table entry information to neighbor nodes of a target node, the target node and the neighbor nodes belonging to a same cross-device link aggregation group, comprises:

5. A system for synchronizing ARP information between MCLAG neighbors, comprising:

6. The system of claim 5, wherein the information monitoring unit is configured to:

7. The system of claim 6, wherein extracting ARP table entry information from ARP messages received by the switch and sending the ARP table entry information to the target node simultaneously with the ARP messages to the neighboring nodes comprises:

if yes, discarding the address resolution protocol table entry information;

8. The system of claim 5, wherein the information synchronization unit is configured to:

9. A terminal, comprising:

a processor;

a memory for storing instructions for execution by the processor;

wherein the processor is configured to perform the method of any one of claims 1-4.

10. A computer-readable storage medium, in which a computer program is stored which, when being executed by a processor, carries out the method according to any one of claims 1-4.