Multicast system and link control method and device thereof

Abstract

The invention relates to the technical field of multicast systems, and discloses a multicast system and a link control method and device thereof, the multicast system comprises a host device and a plurality of neighbor devices, the link control method is applied to the host device, and the link control method comprises the following steps: sending a plurality of ICMP request messages to a specified neighbor device; according to a receiving result of the ICMP response message of the specified neighbor equipment, determining a neighbor link state with the specified neighbor equipment; searching whether the specified neighbor device sending the ICMP response message establishes a PIM neighbor relation with the specified neighbor device, and obtaining a search result; and adjusting the PIM neighbor relation with the specified neighbor equipment according to the neighbor link state and the search result. The link control method of the multicast system supports neighbor link detection with different types of designated neighbor devices, is high in applicability, improves the convergence speed, reliability and efficiency of the multicast system, and optimizes the overall efficiency of establishment of the multicast system.

Description

Technical Field

[0001] The present application relates to the technical field of multicast systems, and in particular to a multicast system and a link control method and device thereof. Background Art

[0002] In a multicast system, the establishment of PIM (Protocol Independent Multicast) neighbor relationships among transmission devices is the basis for the operation of the PIM protocol. The election mechanism relies on the establishment of neighbor relationships. It can be said that the establishment of PIM neighbor relationships directly affects the efficiency of the entire network multicast topology. In addition, changes in PIM neighbor relationships will also lead to changes in the multicast topology in the network. The multicast data loss problem caused by multicast routing convergence after the PIM neighbor status is aged out. The current mainstream solution is to use the BFD (Bidirectional Forwarding Detection) protocol to detect the neighbor link status. However, in real networking, there are scenarios where some devices do not support the BFD function, and the applicability is also limited to the fact that it can only detect single-hop BFD sessions. If there are Layer 2 devices in the link, this solution will fail. Summary of the invention

[0003] In view of this, an embodiment of the present application provides a multicast system and a link control method and apparatus thereof, which can effectively overcome the limitation that link control cannot be performed when a neighboring device does not support the BFD protocol.

[0004] In a first aspect, an embodiment of the present application provides a link control method for a multicast system, wherein the multicast system includes a host device and a plurality of neighbor devices, and the link control method is applied to the host device, including:

[0005] Send multiple ICMP request messages to the specified neighbor device;

[0006] Determine the neighbor link state with the designated neighbor device according to the reception result of the ICMP response message of the designated neighbor device;

[0007] Search whether the designated neighbor device that sends the ICMP response message has established a PIM neighbor relationship with itself, and obtain search results;

[0008] The PIM neighbor relationship with the designated neighbor device is adjusted according to the neighbor link status and the search result.

[0009] In a first possible embodiment of the first aspect, adjusting the PIM neighbor relationship with the designated neighbor device according to the neighbor link state and the search result includes:

[0010] When the neighbor link state is normal, and the designated neighbor device that sends the ICMP response message has established the PIM neighbor relationship with itself, the PIM neighbor relationship with the designated neighbor device is not adjusted;

[0011] When the neighbor link state is normal, but the designated neighbor device that sends the ICMP response message has not established the PIM neighbor relationship with itself, a PIM neighbor relationship is established with the designated neighbor device.

[0012] In a second possible embodiment of the first aspect, adjusting the PIM neighbor relationship with the designated neighbor device according to the neighbor link state and the search result further includes:

[0013] When the neighbor link state is abnormal, and the designated neighbor device that sends the ICMP response message establishes the PIM neighbor relationship with itself, deleting the PIM neighbor relationship with the designated neighbor device;

[0014] When the neighbor link state is abnormal, and the designated neighbor device that sends the ICMP response message has not established the PIM neighbor relationship with itself, no adjustment is performed.

[0015] In a third possible embodiment of the first aspect, after deleting the PIM neighbor relationship with the designated neighbor device, the method further includes:

[0016] The election mechanism of the multicast system is re-triggered to re-elect a new host device.

[0017] In a fourth possible embodiment of the first aspect, determining the neighbor link state with the designated neighbor device according to a result of receiving the ICMP response message of the designated neighbor device includes:

[0018] When the ICMP response message of the designated neighbor device is received, it is determined that the neighbor link state is normal;

[0019] When the ICMP response message of the designated neighbor device is not received for a preset number of consecutive times, it is determined that the neighbor link state is abnormal.

[0020] In a fifth possible embodiment of the first aspect, a neighbor table for describing neighbor information is pre-stored in the host device, and the searching whether the designated neighbor device that sends the ICMP response message has established a PIM neighbor relationship with itself to obtain the search result includes:

[0021] The neighbor table is searched for the neighbor information of the designated neighbor device that sent the ICMP response message to determine the search result.

[0022] In a sixth possible embodiment of the first aspect, the host device dynamically obtains and pre-sets the neighbor information of the designated neighbor device through a network protocol, and when sending multiple ICMP request messages to the designated neighbor device, the method further includes:

[0023] The ICMP request message is sent to each of the designated neighbor devices according to the IP address in the neighbor information, and the next ICMP request message is sent to each of the designated neighbor devices based on a preset interval.

[0024] In a second aspect, an embodiment of the present application provides a link control device for a multicast system, the multicast system comprising a host device and a plurality of neighbor devices, the link control device comprising:

[0025] An ICMP module, configured to send multiple ICMP request messages to a designated neighbor device, and determine a neighbor link state with the designated neighbor device according to a reception result of an ICMP response message from the designated neighbor device;

[0026] The PIM module is used to search whether the designated neighbor device that sends the ICMP response message has established a PIM neighbor relationship with itself, obtain a search result, and adjust the PIM neighbor relationship with the designated neighbor device according to the neighbor link state and the search result.

[0027] In a third aspect, an embodiment of the present application provides a multicast system, including a host device and a plurality of neighbor devices, wherein the host device executes the link control method of the multicast system.

[0028] In a first possible embodiment of the third aspect, the host device and the neighbor device are layer-3 network devices running a multicast protocol.

[0029] The embodiments of the present application have the following beneficial effects:

[0030] A link control method for a multicast system of this embodiment, the multicast system includes a host device and multiple neighbor devices, and the link control method is applied to the host device, including: sending multiple ICMP request messages to a designated neighbor device; determining the neighbor link status with the designated neighbor device according to the reception result of the ICMP response message of the designated neighbor device; searching whether the designated neighbor device that sends the ICMP response message has established a PIM neighbor relationship with itself, and obtaining the search result; adjusting the PIM neighbor relationship with the designated neighbor device according to the neighbor link status and the search result. Based on the above scheme, the host device uses ICMP messages to detect the neighbor link status with the designated neighbor device, supports neighbor link detection with different types of designated neighbor devices, and expands the applicability. The present application also adjusts the PIM neighbor relationship of the designated neighbor device according to the detection results and the search results, improves the convergence speed of the multicast system, optimizes the overall efficiency of the establishment of the multicast system, and improves the reliability and efficiency of the multicast system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 A framework scenario diagram of a multicast system according to an embodiment of the present application is shown;

[0033] Figure 2 A first flow chart of a link control method for a multicast system according to an embodiment of the present application is shown;

[0034] Figure 3 A second flow chart of the link control method of the multicast system according to an embodiment of the present application is shown;

[0035] Figure 4 A schematic structural diagram of a link control device of a multicast system according to an embodiment of the present application is shown.

[0036] Description of main component symbols:

[0037] 100 - multicast system; 110 - host device; 120 - neighbor device; 130 - multicast switch; 400 - link control device of the multicast system; 410 - ICMP module; 420 - PIM module. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0039] The components of the embodiments of the present application generally described and shown in the drawings herein may be arranged and designed in various configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0040] Hereinafter, the terms "including", "having" and their cognates that can be used in various embodiments of the present application are intended only to indicate specific features, numbers, steps, operations, elements, components or a combination of the foregoing items, and should not be understood as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or a combination of the foregoing items or increasing the possibility of one or more features, numbers, steps, operations, elements, components or a combination of the foregoing items. In addition, the terms "first", "second", "third" and the like are only used to distinguish descriptions and cannot be understood as indicating or implying relative importance.

[0041] Unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meanings as those generally understood by those skilled in the art to which the various embodiments of the present application belong. The terms (such as those defined in generally used dictionaries) will be interpreted as having the same meanings as the contextual meanings in the relevant technical field and will not be interpreted as having idealized meanings or overly formal meanings unless clearly defined in the various embodiments of the present application.

[0042] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0043] Generally, if an upstream or downstream neighbor on the multicast distribution tree is unreachable, it will trigger the re-convergence of the multicast device and affect the forwarding of multicast traffic. For example, if the current host device on the shared network segment fails, other devices need to wait for the old neighbor device to age out before triggering the re-election of the host device, which may cause multicast data transmission to be interrupted for a long time. To address the above problems, the current solution is to use the BFD protocol to immediately delete the neighbor relationship after detecting the link failure of the neighbor device to avoid the time loss of waiting timeout. However, in the actual network, there are scenarios where some multicast devices do not support the BFD function. In this case, the BFD one-arm echo function can be relied on to use the loopback operation of the BFD message to detect the connectivity of the forwarding link, but its applicability is limited to the fact that it can only detect single-hop BFD sessions. If there is a Layer 2 device in the link, this solution will fail.

[0044] In view of the situation where there are multicast devices that do not support the BFD protocol in the network, the present application provides a link control method for a multicast system. The link control method can not only trigger the deletion operation of the PIM neighbor relationship with the specified neighbor device when the neighbor link status fails, but also quickly trigger the establishment operation of the PIM neighbor relationship with the specified neighbor device, thereby effectively improving the establishment and convergence speed of the multicast system.

[0045] Before describing the link control method of the multicast system of the present application, the structure of the multicast system is first introduced accordingly.

[0046] Figure 1 A framework scenario diagram of a multicast system 100 according to an embodiment of the present application is shown. Exemplarily, the multicast system 100 includes a host device 110 and a neighbor device 120. Specifically, in the multicast system 100, a multicast switch 130 is connected between the host device 110 and the neighbor device 120. In the multicast system 100, the host device 110 is used to send an ICMP (Internet Control Message Protocol) request message to the neighbor device 120 via the multicast switch 130, and the neighbor device 120 is used to send an ICMP response message to the host device 110 via the multicast switch 130. The multicast switch 130 is used to process multicast data and distribute the data to the neighbor device 120 or the host device 110 connected to the multicast group members. The multicast switch 130 is also used to determine which port the data packet needs to be forwarded to through the multicast address of the multicast group member. It can also detect duplicate data in the multicast tree, thereby reducing network congestion and redundant transmission.

[0047] Optionally, the host device 110 and the neighbor device 120 are three-layer network devices running multicast protocols, i.e., routing devices. In the multicast system 100, the main routing device is the router closest to the multicast source on the multicast tree. The main routing device is responsible for receiving data from the multicast source and forwarding the data to other routers and multicast group members on the multicast tree. The main routing device is responsible for maintaining the structure of the multicast tree and sending Join and Prune messages to other routers to notify multicast group members to join or leave the multicast tree. The main routing device is also used to process Join and Prune messages from other routers to update the structure and member list of the multicast tree. The neighbor routing device is a router close to the multicast group members on the multicast tree. The neighbor routing device is responsible for receiving multicast data from the main routing device and forwarding the data to the multicast group members. The neighbor routing device is used to send Join and Prune messages to the main routing device to request to join or leave the multicast tree. The neighbor routing device is also used to process Join and Prune messages from other routers to update the structure and member list of the multicast tree.

[0048] It can be understood that the role of the main routing device and the neighbor routing device is to cooperate with each other to jointly maintain the structure of the multicast tree and traffic forwarding. The main routing device is responsible for the access of the multicast source and the construction of the multicast tree, and the neighbor routing device is responsible for the access of the multicast group members and the forwarding of data. The entire multicast system 100 enables multicast data to be efficiently transmitted and transferred in the network through maintenance and communication between routers.

[0049] Figure 2 A flow chart of a link control method of a multicast system 100 according to an embodiment of the present application is shown. Exemplarily, the link control method is applied to a host device 110, and specifically includes the following steps:

[0050] S210, sending multiple ICMP request messages to the designated neighbor device 120;

[0051] Exemplarily, the host device 110 sends ICMP request messages to all designated neighbor devices 120 at preset intervals to ensure that the designated neighbor devices 120 send ICMP response messages to the host device 110 after receiving the ICMP request messages.

[0052] For example, in one embodiment, when the host device 110 dynamically obtains and pre-sets the neighbor information of the designated neighbor device 120 through the network protocol and sends multiple ICMP request messages to the designated neighbor device 120, the link control method also includes: sending ICMP request messages to each designated neighbor device 120 according to the IP address in the neighbor information, and sending the next ICMP request message to each designated neighbor device 120 based on a preset interval.

[0053] Specifically, when the host device 110 establishes a PIM neighbor relationship with the designated neighbor device 120, the host device 110 stores the neighbor information of the designated neighbor device 120 in the neighbor table, and the neighbor information includes the neighbor IP address, identifier, association information and protocol parameters, etc. The destination IP address of the ICMP request message is the IP address of each designated neighbor device 120. The characteristics of the ICMP protocol determine that the designated neighbor device 120 will send an ICMP response message to the host device 110 when it receives the ICMP request message. The host device 110 uses the above mechanism as a basis for judging the link status of the neighbor device 120. Optionally, the preset interval can be set to 10 seconds, and the preset number of times can be set to 3 times.

[0054] It can be understood that the host device 110 detects the neighbor link status of the designated neighbor device 120 through the ICMP protocol, which not only realizes the neighbor link status detection when the neighbor device 120 does not support the BFD protocol, but also avoids the problem that the BFD single-arm echo function cannot perform multi-hop detection.

[0055] S220 , determining the neighbor link state with the designated neighbor device 120 according to the reception result of the ICMP response message of the designated neighbor device 120 .

[0056] Exemplarily, when the host device 110 receives an ICMP response message, it can be confirmed that the neighbor link status is normal. If the host device 110 sends ICMP request messages for a preset number of times and still does not receive any ICMP response message, it can be determined that the neighbor link status is abnormal.

[0057] For example, in one embodiment, the link control method determines the neighbor link status with the specified neighbor device 120 based on the reception result of the ICMP response message of the specified neighbor device 120, including: when the ICMP response message of the specified neighbor device 120 is received, the neighbor link status is determined to be normal; when the ICMP response message of the specified neighbor device 120 is not received for a preset number of consecutive times, the neighbor link status is determined to be abnormal.

[0058] S230, searching whether the designated neighbor device 120 that sent the ICMP response message has established a PIM neighbor relationship with itself, and obtaining a search result;

[0059] Exemplarily, when the host device 110 receives an ICMP response message from the designated neighbor device 120, it searches the neighbor table for the IP address of the designated neighbor device 120 that sends the ICMP response message based on the pre-set neighbor information of the designated neighbor device 120. If so, it is considered that the host device 110 has established a PIM neighbor relationship with the designated neighbor device 120 that sends the ICMP response message.

[0060] For example, in one embodiment, a neighbor table for describing neighbor information is pre-stored in the host device 110. The link control method searches whether the designated neighbor device 120 that sends the ICMP response message has established a PIM neighbor relationship with itself to obtain the search result, including: searching the neighbor table for neighbor information of the designated neighbor device that sends the ICMP response message to determine the search result.

[0061] S240: Adjust the PIM neighbor relationship with the designated neighbor device 120 according to the neighbor link status and the search result.

[0062] Exemplarily, the host device 110 adds or deletes the PIM neighbor device 120 according to the normal and faulty results of the neighbor link status detection and the search result of whether to establish a PIM neighbor relationship with the designated neighbor device 120 that sent the ICMP response message.

[0063] For example, in one embodiment, the link control method adjusts the PIM neighbor relationship with the designated neighbor device 120 according to the neighbor link status and the search results, including: when the neighbor link status is normal and the designated neighbor device 120 that sends the ICMP response message has established a PIM neighbor relationship with itself, the PIM neighbor relationship with the designated neighbor device 120 is not adjusted; when the neighbor link status is normal, but the designated neighbor device 120 that sends the ICMP response message has not established a PIM neighbor relationship with itself, a PIM neighbor relationship with the designated neighbor device 120 is established.

[0064] For example, in one embodiment, the link control method adjusts the PIM neighbor relationship with the designated neighbor device 120 according to the neighbor link status and search results, and also includes: when the neighbor link status is abnormal and the designated neighbor device 120 that sends the ICMP response message has established a PIM neighbor relationship with itself, deleting the PIM neighbor relationship with the designated neighbor device 120; when the neighbor link status is abnormal and the designated neighbor device 120 that sends the ICMP response message has not established a PIM neighbor relationship with itself, no adjustment is made.

[0065] Specifically, when the neighbor link status is normal, the host device 110 determines whether the PIM neighbor device 120 with the IP address has been established by searching the neighbor table according to the IP address of the designated neighbor device 120 contained in the ICMP response message. When the IP address of the corresponding designated neighbor device 120 can be found, no processing is performed, and the current link is directly exited to wait for the next feedback result. If it cannot be found, it means that the PIM neighbor relationship has not been established. The corresponding PIM neighbor relationship is directly established according to the IP address of the designated neighbor device 120, so as to avoid the situation that the host device 110 receives the PIM protocol message of the neighbor device 120, but the PIM neighbor relationship with the neighbor device 120 is directly ignored when the PIM neighbor relationship is not established, so as to ensure the rapid establishment of multicast routing. When the neighbor link status is faulty and the IP address of the corresponding designated neighbor device 120 cannot be found, the current link is directly exited to wait for the next feedback result. When the IP address of the corresponding designated neighbor device 120 is found, the PIM neighbor device 120 is directly deleted.

[0066] Specifically, each host device 110 that has the PIM protocol enabled will send HELLO messages at a certain period in the network segment. After receiving the HELLO messages, other devices will check the parameter information of the neighbor device 120 contained in the HELLO messages. If the parameters of both parties are consistent, a PIM neighbor relationship is established. Optionally, the host device 110 can also quickly establish a PIM neighbor relationship with a specified neighbor device 120, that is, skip all checking steps, assume that the neighbor parameters are consistent, and directly store the preset neighbor IP address and other information directly in the neighbor table.

[0067] Exemplarily, if the host device 110 is set by the multicast system 100 through an election mechanism, after deleting the PIM neighbor device 120, the election mechanism of the multicast system 100 is triggered to re-elect, thereby achieving rapid convergence of multicast routing.

[0068] For example, in one embodiment, after the PIM neighbor relationship with the designated neighbor device 120 is deleted, the link control method further includes: re-triggering the election mechanism of the multicast system 100 to re-elect a new host device 110 .

[0069] Exemplarily, the host device 110 can determine whether to re-detect and process neighbor links according to user needs and actual conditions. If the host device 110 only needs to delete the PIM neighbor relationship of the designated neighbor device 120 that is detected abnormally once, or detects that the neighbor link status is normal and quickly establishes a PIM neighbor relationship with the designated neighbor device 120, it is not necessary to re-detect and process neighbor links. If it is necessary to continuously and quickly add and delete PIM neighbors according to the link detection status, the host device 110 needs to re-detect and process neighbor links.

[0070] Specifically, Figure 3 As shown, the link control method of the multicast system 100 includes the following process: S310, the host device 110 sends an ICMP request message with the destination IP address of the designated neighbor device 120 once within a preset interval; S320, it is determined that after sending multiple ICMP request messages, no ICMP reply message from the designated neighbor device 120 is received; if not, step S340 is performed, and if yes, step S330 is performed; S330, it is determined that the neighbor link state is a fault state; S340, it is found whether the designated neighbor device 120 that sends the ICMP reply message has established a PIM neighbor relationship with the host device 110, and if Otherwise, proceed to step S350; if yes, proceed to step S360; S350, determine whether the neighbor link status is a faulty status; if otherwise, proceed to step S310; if yes, proceed to step S370; S360, determine whether the neighbor link status is a normal status; if otherwise, proceed to step S310; if yes, proceed to step S380; S370, delete the PIM neighbor relationship with the specified neighbor device 120; S380, establish a PIM neighbor relationship with the specified neighbor device 120; S390, determine whether to re-detect and process the link status; if otherwise, end; if yes, proceed to step S310.

[0071] Figure 4 A schematic structural diagram of a link control device 400 of a multicast system according to an embodiment of the present application is shown. Exemplarily, the link control device 400 of the multicast system includes:

[0072] The ICMP module 410 is used to send multiple ICMP request messages to the designated neighbor device 120 , and determine the neighbor link state with the designated neighbor device 120 according to the reception result of the ICMP response message of the designated neighbor device 120 .

[0073] The PIM module 420 is used to search whether the designated neighbor device 120 that sends the ICMP response message has established a PIM neighbor relationship with itself, obtain the search result, and adjust the PIM neighbor relationship with the designated neighbor device 120 according to the neighbor link state and the search result.

[0074] It can be understood that the device of this embodiment corresponds to the link control method of the multicast system of the above embodiment, and the options in the above embodiment are also applicable to this embodiment, so they will not be described repeatedly here.

[0075] In several embodiments provided in the present application, it should be understood that the disclosed devices and methods can also be implemented in other ways. The device embodiments described above are merely schematic. For example, the flowcharts and structure diagrams in the accompanying drawings show the possible architecture, functions and operations of the devices, methods and computer program products according to multiple embodiments of the present invention. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the module, a program segment or a part of a code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in an alternative implementation, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the structure diagram and / or the flow chart, and the combination of boxes in the structure diagram and / or the flow chart, can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0076] In addition, the functional modules or units in the various embodiments of the present invention may be integrated together to form an independent part, or each module may exist independently, or two or more modules may be integrated to form an independent part.

[0077] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a smart phone, a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0078] The above are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be covered by the protection scope of the present application.

Claims

1. A link control method for a multicast system, characterized in that: The multicast system includes a host device and a plurality of neighbor devices, and the link control method is applied to the host device, including: Send multiple ICMP request messages to the specified neighbor device; Determine the neighbor link state with the designated neighbor device according to the reception result of the ICMP response message of the designated neighbor device; Search whether the designated neighbor device that sends the ICMP response message has established a PIM neighbor relationship with itself, and obtain search results; The PIM neighbor relationship with the designated neighbor device is adjusted according to the neighbor link status and the search result.

2. The link control method of a multicast system according to claim 1, characterized in that: The adjusting the PIM neighbor relationship with the designated neighbor device according to the neighbor link state and the search result includes: When the neighbor link state is normal, and the designated neighbor device that sends the ICMP response message has established the PIM neighbor relationship with itself, the PIM neighbor relationship with the designated neighbor device is not adjusted; When the neighbor link state is normal, but the designated neighbor device that sends the ICMP response message has not established the PIM neighbor relationship with itself, a PIM neighbor relationship is established with the designated neighbor device.

3. The link control method of a multicast system according to claim 1 or 2, characterized in that: The adjusting the PIM neighbor relationship with the designated neighbor device according to the neighbor link state and the search result further includes: When the neighbor link state is abnormal, and the designated neighbor device that sends the ICMP response message establishes the PIM neighbor relationship with itself, deleting the PIM neighbor relationship with the designated neighbor device; When the neighbor link state is abnormal, and the designated neighbor device that sends the ICMP response message has not established the PIM neighbor relationship with itself, no adjustment is performed.

4. The link control method of a multicast system according to claim 3, characterized in that: After deleting the PIM neighbor relationship with the designated neighbor device, the method further includes: The election mechanism of the multicast system is re-triggered to re-elect a new host device.

5. The link control method of a multicast system according to claim 1, characterized in that: The determining, according to the reception result of the ICMP response message of the designated neighbor device, the neighbor link state with the designated neighbor device comprises: When the ICMP response message of the designated neighbor device is received, it is determined that the neighbor link state is normal; When the ICMP response message of the designated neighbor device is not received for a preset number of consecutive times, it is determined that the neighbor link state is abnormal.

6. The link control method of a multicast system according to claim 1, characterized in that: The host device pre-stores a neighbor table for describing neighbor information, and the searching whether the designated neighbor device that sends the ICMP response message has established a PIM neighbor relationship with itself to obtain the search result includes: The neighbor table is searched for the neighbor information of the designated neighbor device that sent the ICMP response message to determine the search result.

7. The link control method of a multicast system according to claim 1, characterized in that: The host device dynamically obtains and pre-sets the neighbor information of the designated neighbor device through a network protocol, and when sending multiple ICMP request messages to the designated neighbor device, it also includes: The ICMP request message is sent to each of the designated neighbor devices according to the IP address in the neighbor information, and the next ICMP request message is sent to each of the designated neighbor devices based on a preset interval.

8. A link control device for a multicast system, characterized in that: The multicast system includes a host device and a plurality of neighbor devices, and the link control device includes: An ICMP module, used for sending multiple ICMP request messages to a designated neighbor device, and determining a neighbor link state with the designated neighbor device according to a reception result of an ICMP response message of the designated neighbor device; The PIM module is used to search whether the designated neighbor device that sends the ICMP response message has established a PIM neighbor relationship with itself, obtain a search result, and adjust the PIM neighbor relationship with the designated neighbor device according to the neighbor link state and the search result.

9. A multicast system, characterized in that: The invention comprises a host device and a plurality of neighbor devices, wherein the host device executes the link control method of the multicast system according to any one of claims 1 to 7.

10. The multicast system according to claim 9, characterized in that: The host device and the neighbor device are layer 3 network devices running a multicast protocol.

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