A method for constructing a cascaded switching network, network maintenance, and routing maintenance

Abstract

The present invention belongs to the field of airborne network technology, and specifically relates to a method for constructing a cascaded switching network, network maintenance, and routing maintenance. First is the cascaded automatic construction process. After the switches participating in the cascaded construction complete initialization, they automatically enter the construction process, simply, efficiently, and reliably realizing the construction of the cascaded network. Second is the cascaded network automatic maintenance mechanism. For switches, cascaded network maintenance refers to the maintenance of cascaded network link information. After the cascaded construction is successful, the correctness of the link information is maintained through link up / down interruption processing and periodic transmission of link switching frames. Third is the cascaded routing automatic maintenance mechanism, which means that after the cascaded construction is successful, the switches automatically configure cascaded routes to achieve cross-cascaded communication and avoid faults such as broadcast storms, clock synchronization conflicts, and link resets caused by configuration errors.

Description

Technical Field

[0001] The present invention belongs to the technical field of airborne networks, and particularly relates to a method for constructing a cascaded switching network, network maintenance, and routing maintenance. Background Art

[0002] With the increasing demand for high-speed data communication in airborne equipment, the FC network with high bandwidth and low latency characteristics has become the first choice for constructing a new generation of airborne avionics networks. Three basic topologies are defined in the FC protocol to construct an FC network: point-to-point communication between two N ports (ordinary node ports without arbitrated loop function); an arbitrated loop communication network with an internal connection of a group of L ports (arbitrated loop ports) using a ring topology; and a switched network with an internal connection of a group of N ports (ordinary node ports without arbitrated loop function) using an FC switch. The point-to-point communication network has a small scale, the arbitrated loop communication network has poor reliability, while the switched network has a large scale and allows multiple devices to perform high-speed communication at the same time, becoming the mainstream topology for the development of FC networks.

[0003] In a switched network, a switched network constructed by cascading multiple switches has the following advantages compared with a single-switch network: 1. It has better scalability, that is, it supports connecting more N ports; 2. It has higher reliability; 3. It is easier to upgrade, only requiring adding a new switch without the need to re-develop to replace the original switch.

[0004] There is a need for a cascaded switching network with a large number of electronic network ports and high reliability. Summary of the Invention

[0005] In view of this, the present invention proposes a method for constructing a cascaded switching network. The cascaded automatic construction process enables the switches participating in the cascaded construction to automatically enter the construction process after initialization, and can simply, efficiently, and reliably implement the construction of the cascaded network.

[0006] To achieve the above technical objectives, the specific technical solutions adopted by the present invention are as follows:

[0007] A method for constructing a cascaded switching network, which realizes the construction of at least two switches into a cascaded network based on the resident software of the switch, including the following steps:

[0008] Step 1, the cascaded ports go online, and the resident software on each switch sends a cascaded construction request frame;

[0009] Step 2, cascaded parameter negotiation. After the resident software on each switch receives the cascaded construction request frame from the peer switch, it performs cascaded parameter negotiation. If the negotiation is successful, it sends a cascaded construction response frame. If the negotiation fails and the number of failure times exceeds the threshold, it exits the construction process;

[0010] Step 3, cascade request confirmation. When the software resident on the switch receives the cascade construction response frame sent by the peer switch, it detects the response frame. If it is correct, it proceeds with the master switch election and the master cascade link election; if it is incorrect, it exits the construction process.

[0011] Step 4, configure cascade information. After the master switch election and the master cascade link election are carried out, the number of cascade ports and the cascade port numbers are configured into the hardware registers of each switch, and the cascade function of each switch is enabled to complete the cascade construction process.

[0012] Further, in the said Step 1, the data structure of the cascade construction request frame includes the local domain ID, the switch link status broadcast period, the configuration scheme number, the logical version number, the software version number, the number of ports K used by the cascade ports, and the list of port numbers used by the cascade ports.

[0013] Further, in the said Step 2, the cascade parameters are used to negotiate the content of the cascade construction request frame, and the negotiation strategies are the same for all information except the requirement for the local domain ID; the data structure of the cascade construction response frame includes the local domain ID, the switch link status broadcast period, the configuration scheme number, the logical version number, the software version number, the number of ports K used by the cascade ports, the list of port numbers used by the local switch cascade ports, and the list of port numbers used by the peer switch cascade ports.

[0014] Further, in the said Step 3, the master switch election strategy and the master cascade link election strategy are as follows: the switch with the smaller local domain ID is elected as the master switch;

[0015] The one with the smaller port number used by the cascade port is elected as the master cascade link.

[0016] Further, in the said Step 4, the number of cascade ports configured into the hardware register is consistent with the number of ports K used by the cascade ports in the cascade construction request frame; the cascade port numbers configured into the hardware register are consistent with the list of port numbers used by the cascade ports in the cascade construction request frame.

[0017] Meanwhile, the present invention also proposes a cascade network maintenance method based on the above cascade switching network construction method, which is characterized in that:

[0018] When the underlying logic reports an interruption,

[0019] Judge the interruption type;

[0020] If the interruption type is a link status interruption,

[0021] Judge the type of link state interruption. If the type of link state interruption is the online of cascade port, increment the number of online cascade ports by 1, assign it to the cascade port list, and perform hardware configuration;

[0022] If the type of link state interruption is the offline of cascade port, decrement the number of online cascade ports by 1, and then judge the number of online cascade ports. If it is greater than 0, update the cascade port list and perform hardware configuration; when the number of online cascade ports is equal to 0, disconnect the cascade network, clear the cascade configuration, and clear all the peer link states in the periodic link broadcast data structure.

[0023] If the type of link state interruption is the online / offline of F port, call the FC frame sending function in the switch driver to send link exchange frames;

[0024] The link exchange frame includes the local domain ID, the switch clock synchronization conflict flag, the clock synchronization primitive, and the port link state list.

[0025] The hardware configuration includes configuring the online cascade port number register, the cascade port number register, the cascade port enable register, the multicast message buffer, and the clock synchronization primitive forwarding enable register.

[0026] Further, when the number of online cascade ports is equal to 0, the switches also periodically send the link exchange frames to each other.

[0027] Meanwhile, the present invention also proposes a cascade route maintenance method based on the above cascade network maintenance method, which is characterized in that:

[0028] Judge the to-be-configured route type of the cascade network;

[0029] If the configured route type is the broadcast route, the main switch broadcasts the route destination port list and only retains a pair of cascade links to forward the broadcast to the slave switches;

[0030] If the configured route type is the multicast route, when the multicast destination port list contains the cascade switch ports, only select a pair of cascade links to configure as the multicast route destination ports; meanwhile, adopt the load balancing strategy, modulo the multicast message number by the number of online cascade ports, and distribute the multicast messages to a pair of cascade links for route configuration;

[0031] If the configured route type is the clock synchronization route, only enable one cascade port to execute the clock synchronization forwarding function, and disable the clock synchronization forwarding functions of other cascade ports.

[0032] Adopting the above technical solutions, the present invention can bring the following beneficial effects:

[0033] One is the cascading automatic construction process. After the switch participating in the cascading construction completes initialization, it automatically enters the construction process, simply, efficiently, and reliably realizing the construction of the cascading network. The second is the cascading network automatic maintenance mechanism. For the switch, the cascading network maintenance refers to the maintenance of the cascading network link information. After the cascading construction is successful, the correctness of the link information is maintained by handling the interruption of the link going up and down and periodically sending link switching frames. The third is the cascading routing automatic maintenance mechanism, which means that after the cascading construction is successful, the switch automatically configures the cascading route to achieve cross-cascading communication, and pays attention to avoiding faults such as broadcast storms, clock synchronization conflicts, and link resets caused by configuration errors. Overall, it expands the network scale, improves the reliability of important node communication, and as a component of the switch software, this method does not generate target code separately for upgrade and maintenance, saving labor costs and R & D costs, improving R & D efficiency, and reducing the management and maintenance of the product's outfield technical status. Brief Description of the Drawings

[0034] To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0035] Figure 1 It is the specific flowchart of a cascading switching network construction method in the specific implementation manner of the present invention;

[0036] Figure 2 It is the automatic maintenance mechanism diagram in a cascading network maintenance method in the specific implementation manner of the present invention;

[0037] Figure 3 It is the automatic maintenance mechanism diagram in a cascading routing maintenance method in the specific implementation manner of the present invention. Specific Embodiment

[0038] The embodiments of the present disclosure will be described in detail below with reference to the drawings.

[0039] The following describes the embodiments of the present disclosure through specific examples, and those skilled in the art can easily understand the other advantages and effects of the present disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. The present disclosure can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure without creative efforts belong to the scope of protection of the present disclosure.

[0040] It should be noted that the following describes various aspects of the embodiments within the scope of the appended claims. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is illustrative only. Based on the present disclosure, those skilled in the art should understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. Additionally, this device and / or this method can be implemented using other structures and / or functionality in addition to one or more of the aspects described herein.

[0041] It should also be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present disclosure in a schematic manner. The diagrams only show the components related to the present disclosure, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in its actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0042] In addition, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0043] In an embodiment of the present invention, a method for constructing a cascaded switching network is proposed, which is characterized in that at least two switches are constructed into a cascaded network based on the resident software of the switch, including the following steps:

[0044] Step 1, the cascaded ports go online, and the resident software on each switch sends a cascaded construction request frame;

[0045] Step 2, cascade parameter negotiation. After the software resident on each switch receives the cascade construction request frame from the peer switch, it conducts cascade parameter negotiation. If the negotiation is successful, it sends a cascade construction response frame. If the negotiation fails and the number of failure times exceeds the threshold, it exits the construction process;

[0046] Step 3, cascade request confirmation. When the software resident on the switch receives the cascade construction response frame sent by the peer switch, it detects the response frame. If it is correct, it conducts the master switch election and the master cascade link election. If it is incorrect, it exits the construction process;

[0047] Step 4, configure cascade information. After conducting the master switch election and the master cascade link election, configure the number of cascade ports and the cascade port numbers into the hardware registers of each switch, and enable the cascade function of each switch to complete the cascade construction process.

[0048] In this embodiment, in the said Step 1, the data structure of the cascade construction request frame includes the local domain ID, the switch link status broadcast period, the configuration scheme number, the logical version number, the software version number, the number of ports K used by the cascade ports, and the list of port numbers used by the cascade ports.

[0049] In this embodiment, in the said Step 2, the cascade parameters are used to negotiate the content of the cascade construction request frame, and the negotiation policies are the same for all information except the requirement for the local domain ID; the data structure of the cascade construction response frame includes the local domain ID, the switch link status broadcast period, the configuration scheme number, the logical version number, the software version number, the number of ports K used by the cascade ports, the list of port numbers used by the local switch cascade ports, and the list of port numbers used by the peer switch cascade ports.

[0050] In this embodiment, in the said Step 3, the master switch election policy and the master cascade link election policy are: the switch with the smaller local domain ID is elected as the master switch;

[0051] The one with the smaller port number used by the cascade port is elected as the master cascade link.

[0052] In this embodiment, in the said Step 4, the number of cascade ports configured into the hardware register is consistent with the number of ports K used by the cascade ports in the cascade construction request frame; the cascade port numbers configured into the hardware register are consistent with the list of port numbers used by the cascade ports in the cascade construction request frame.

[0053] Based on the same inventive concept, in one embodiment, the present invention also proposes a cascade network maintenance method based on the above cascade switching network construction method, specifically:

[0054] When the underlying logic reports an interruption,

[0055] Determine the type of interruption;

[0056] If the interruption type is link status interruption,

[0057] Determine the type of link status interruption. If the type of link status interruption is cascaded port online, increment the number of online cascaded ports by 1, assign it to the cascaded port list, and perform hardware configuration;

[0058] If the type of link status interruption is cascaded port offline, decrement the number of online cascaded ports by 1, then determine the number of online cascaded ports. If it is greater than 0, update the cascaded port list for hardware configuration; when the number of online cascaded ports is equal to 0, disconnect the cascaded network, clear the cascaded configuration, and clear all peer link statuses in the periodic link broadcast data structure.

[0059] If the type of link status interruption is F port online / offline, call the FC frame sending function in the switch driver to send link exchange frames;

[0060] The link exchange frame includes a local domain ID, a switch clock synchronization conflict flag, a clock synchronization primitive, and a port link status list.

[0061] The hardware configuration includes configuring the online cascaded port number register, the cascaded port number register, the cascaded port enable register, the multicast message buffer, and the clock synchronization primitive forwarding enable register.

[0062] In this embodiment, when the number of online cascaded ports is equal to 0, the switches also periodically send each other the link exchange frames.

[0063] Based on the same inventive concept, in one embodiment, the present invention also proposes a cascaded route maintenance method based on the above cascaded network maintenance method, specifically:

[0064] Determine the to-be-configured route type of the cascaded network;

[0065] If the configured route type is broadcast route, the main switch broadcasts the route destination port list and only retains a pair of cascaded links to forward the broadcast to the slave switches;

[0066] If the configured route type is multicast route, when the multicast destination port list contains cascaded switch ports, only select a pair of cascaded links to configure as the multicast route destination ports; at the same time, adopt a load balancing strategy, modulo the multicast message number by the number of online cascaded ports and take the remainder, and distribute the multicast messages to a pair of cascaded links for route configuration;

[0067] If the configured route type is clock synchronization route, only enable one cascaded port to perform the clock synchronization forwarding function, and disable the clock synchronization forwarding functions of other cascaded ports.

[0068] To better understand the present invention, the above embodiments will be further described below in conjunction with the accompanying drawings and applications in an airborne network.

[0069] As Figure 1 shown, the process for automatically constructing a cascaded switching network is as follows:

[0070] Step 1, The cascaded port goes online and sends a cascaded construction request frame.

[0071] Step 2, Cascaded parameter negotiation. After receiving the cascaded construction request frame, perform cascaded parameter negotiation. If the negotiation is successful, send a cascaded construction response frame. If the negotiation fails and the number of failure times exceeds the threshold, exit the construction process.

[0072] Step 3, Cascaded request confirmation. After receiving the cascaded construction response frame, detect the response frame. If it is correct, perform the election of the main switch and the main cascaded link. If it is incorrect, exit the construction process.

[0073] Step 4, Configure cascaded information. Configure the number of cascaded ports and the cascaded port numbers into the hardware register, and enable the cascaded function to complete the cascaded construction process.

[0074] In the said Step 1, the data structure of the cascaded construction request frame includes the local domain ID, the switch link status broadcast period, the configuration scheme number, the logical version number, the software version number, the number K of F physical ports used by the E port, and the list of F physical port numbers used by the E port (cascaded port). The data structure of the cascaded construction request frame is shown in Table 1.

[0075] Table 1 Data Structure of Cascaded Construction Request Frame

[0076]

[0077]

[0078] In the said Step 2, the content of the cascaded parameter negotiation is the content of the cascaded construction request frame. Among them, except that the local domain ID is required to be different, other information is required to be the same. In addition, the data structure of the cascaded construction response frame includes the local domain ID, the switch link status broadcast period, the configuration scheme number, the logical version number, the software version number, the number K of F physical ports used by the E port, the list of F physical port numbers used by the local switch E port, and the list of F physical port numbers used by the peer switch E port. The data structure of the cascaded construction response frame is shown in Table 2.

[0079] Table 2 Data Structure of Cascaded Construction Response Frame

[0080]

[0081] In step 3, for the election strategy of the main switch and the main cascaded link, the one with a smaller local domain ID is elected as the main switch, and the one with a smaller F physical port number used by the E port is elected as the main cascaded link.

[0082] In step 4, the number of cascaded ports configured into the hardware register is consistent with the number K of F physical ports used by the E port in the cascaded construction request frame, and the cascaded port numbers configured into the hardware register are consistent with the list of F physical port numbers used by the E port in the cascaded construction request frame.

[0083] As Figure 2 shown, the automatic maintenance mechanism of the cascaded network is as follows:

[0084] Step 1, the cascaded construction is completed;

[0085] Step 2, wait for the underlying logic to report an interrupt;

[0086] Step 3, judge the type of the interrupt. If it is a clock assistance interrupt, go to step 4; if it is a link status interrupt, go to step 5;

[0087] Step 4, judge whether the clock count reaches the switching period. If so, call the FC frame sending function in the switch driver to send a link switching frame and clear the clock count. If not, perform an increment operation on the count;

[0088] Step 5, judge the type of the link status interrupt. If the E port goes online, go to step 6; if the E port goes offline, go to step 7; if the F port goes up or down, go to step 8;

[0089] Step 6, increment the number of online cascaded ports by 1, assign it to the cascaded port list, and perform hardware configuration;

[0090] Step 7, decrement the number of online cascaded ports by 1, and then judge the number of online cascaded ports. If it is greater than 0, update the cascaded port list and perform hardware configuration; if it is equal to 0, disconnect the cascaded network, clear the cascaded configuration, and clear all the peer link statuses in the periodic link broadcast data structure.

[0091] Step 8, call the FC frame sending function in the switch driver to send a link switching frame.

[0092] In step 4, the link switching frame includes the local domain ID, the switch clock synchronization conflict flag, the clock synchronization primitive, and the port link status list. The data structure of the link switching frame is shown in Table 3.

[0093] Table 3 Data Structure of the Link Switching Frame

[0094]

[0095]

[0096] In step 6, the hardware configuration includes configuring the online cascaded port number register, the number of cascaded ports register, the cascaded port enable register, the multicast message buffer, and the clock synchronization primitive forwarding enable register.

[0097] In step 7, the hardware configuration is the same as that in step 6; clear the peer link status in the periodic link broadcast data structure to prevent the switch from broadcasting incorrect link information, which may cause the node to fail to reconnect to the network, and ensure the correctness of the cascaded network automatic maintenance mechanism.

[0098] In step 8, the link exchange frame is the same as that in step 4.

[0099] As Figure 3 shown, the cascaded routing automatic maintenance mechanism is as follows:

[0100] Step 1, after the cascaded construction is successful, determine the routing type to be configured for deterministic configuration. If it is a broadcast switch cascaded routing, go to step 2; if it is a multicast switch cascaded routing, go to step 3; if it is a clock synchronization cascaded routing, go to step 4;

[0101] Step 2, the broadcast routing destination port is all ports. After the cascaded construction is successful, the main switch's broadcast routing destination port list can only retain a pair of cascaded links (main link) to forward broadcasts to the slave switch. Otherwise, it will form a loop and cause a broadcast storm;

[0102] Step 3, multicast switch cascaded routing means that when the multicast destination port list contains the cascaded switch ports, to avoid forming a loop and causing a link reset failure, only a pair of cascaded links can be selected to be configured as the multicast routing destination ports. In addition, to prevent the main cascaded link from being overloaded (the main cascaded link is already used for broadcast routing and clock synchronization routing), we adopt a load balancing strategy and distribute the multicast messages to a pair of cascaded links for routing configuration according to the remainder of the multicast message number modulo the number of online cascaded ports;

[0103] Step 4, according to the FC-SW-2 protocol, the switch logically enables the clock synchronization forwarding function for all ports by default. After the cascaded construction is successful, only one cascaded port (the port of the main cascaded link is currently used) can be enabled for the clock synchronization forwarding function, and the clock synchronization forwarding functions of other cascaded ports must be prohibited. Otherwise, it will form a loop and cause a clock synchronization conflict.

[0104] As described above, it is only the specific implementation manner of the present disclosure. However, the protection scope of the present disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present disclosure should be covered within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.

Claims

1. A method for constructing a cascaded switching network, characterized in that The implementation of the resident software based on the switch to build at least two switches into a cascaded network includes the following steps: Step 1: The cascaded ports go online. The resident software on each switch sends a cascaded network construction request frame. The data structure of the cascaded network construction request frame includes the local domain ID, the switch link status broadcast period, the configuration scheme number, the logical version number, the software version number, the number of ports K used by the cascaded ports, and the port number list used by the cascaded ports. Step 2: Cascaded parameter negotiation. After the resident software on each switch receives the cascaded network construction request frame from the peer switch, it conducts cascaded parameter negotiation. If the negotiation is successful, it sends a cascaded network construction response frame. If the negotiation fails and the number of failure times exceeds the threshold, it exits the construction process. The cascaded parameters are used to negotiate the content of the cascaded network construction request frame, and the negotiation strategies are the same for all information except the requirement for the local domain ID. The data structure of the cascaded network construction response frame includes the local domain ID, the switch link status broadcast period, the configuration scheme number, the logical version number, the software version number, the number of ports K used by the cascaded ports, the port number list used by the local switch's cascaded ports, and the port number list used by the peer switch's cascaded ports. Step 3: Cascaded request confirmation. When the resident software on the switch receives the cascaded network construction response frame sent by the peer switch, it detects the response frame. If it is correct, it conducts the master switch election and the master cascaded link election. If it is incorrect, it exits the construction process. Step 4: Configure cascaded information. After the master switch election and the master cascaded link election, the number of cascaded ports and the cascaded port numbers are configured into the hardware registers of each switch, and the cascaded function of each switch is enabled to complete the cascaded network construction process. The number of cascaded ports configured into the hardware register is the same as the number of ports K used by the cascaded ports in the cascaded network construction request frame. The cascaded port numbers configured into the hardware register are the same as the port number list used by the cascaded ports in the cascaded network construction request frame.

2. The method for constructing a cascaded switching network according to claim 1, wherein In the said Step 3, the master switch election strategy and the master cascaded link election strategy are: the switch with the smaller local domain ID is elected as the master switch. The one with the smaller port number used by the cascaded port is elected as the master cascaded link.

3. A cascaded network maintenance method for the cascaded switch network construction method according to any one of claims 1-2, characterized in that: When the underlying logic reports an interruption, Judge the interruption type; If the interruption type is a link status interruption, Judge the type of the link status interruption. If the type of the link status interruption is the online of the cascaded port, the number of online cascaded ports is incremented by 1, assigned to the cascaded port list, and hardware configuration is performed; If the type of the link status interruption is the offline of the cascaded port, the number of online cascaded ports is decremented by 1, and then judge the number of online cascaded ports. If it is greater than 0, update the cascaded port list and perform hardware configuration; when the number of online cascaded ports is equal to 0, disconnect the cascaded network, clear the cascaded configuration, and clear all the peer link statuses in the periodic link broadcast data structure; If the type of the link status interruption is the online / offline of the F port, call the FC frame sending function in the switch driver to send a link exchange frame. The link exchange frame includes a local domain ID, a switch clock synchronization conflict flag, a clock synchronization primitive, and a port link status list; The hardware configuration includes a configured online cascaded port number register, a cascaded port number register, a cascaded port enable register, a multicast message buffer, and a clock synchronization primitive forwarding enable register.

4. The cascaded network maintenance method according to claim 3, wherein: When the number of online cascaded ports is equal to 0, the switches also periodically send the link exchange frames to each other.

5. A cascaded route maintenance method for the cascaded network maintenance method according to claim 4, wherein: Judge the routing type to be configured for the cascaded network; If the configured routing type is a broadcast route, the main switch broadcasts a routing destination port list and only retains a pair of cascaded links to forward the broadcast to the slave switches; If the configured routing type is a multicast route, when the multicast destination port list includes cascaded switch ports, only select a pair of cascaded links to configure as the multicast routing destination ports; at the same time, adopt a load balancing strategy, and modulo the multicast message number by the number of online cascaded ports to allocate the multicast message to a certain pair of cascaded links for routing configuration; If the configured routing type is a clock synchronization route, only enable one cascaded port to perform the clock synchronization forwarding function, and disable the clock synchronization forwarding functions of other cascaded ports.

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