Small-particle dual-homing protection switching method and system based on three-way aps code negotiation

Abstract

The application discloses a small-particle dual-homing protection switching method and system based on three-direction APS code negotiation, and relates to the technical field of communication small-particle service protection switching. The method comprises the following steps: the dual-homing master node and the dual-homing backup node in the same group communicate through DNI signaling messages, and the dual-homing nodes communicate with the nodes in different groups through APS codes; the DNI signaling messages and the APS codes are used for informing the path state information and the switching information of the local end to the opposite end, and performing protection switching according to the DNI and / or the APS code. Based on the characteristics of the small-particle service, the application proposes the definition of the related fields in the DNI messages between the dual-homing nodes, and on the basis, proposes a small-particle dual-homing protection scheme based on three-direction APS code negotiation. According to the scheme, the targeted switching is performed according to the fault node, the small-particle cross-domain service protection demand is met, the operation of switching the two ends of any fault is not needed, and the troubleshooting efficiency can be improved.

Description

Technical Field

[0001] This invention relates to the field of protection switching technology for small-granularity communication services, specifically to a small-granularity dual-homing protection switching method and system based on three-way APS code negotiation. Background Technology

[0002] Regarding the technical fields of MTN (Metro Transport Network) and FGU (Fine Granularity Unit), the G.83 series of standard recommendations were released in 2020, among which the protection standard is G.8331-202202, defining a 1+1 end-to-end protection model, applying the G.8331 metropolitan area network protection model to... Figure 1 Cross-domain scenarios in [the context of something]. See [the source]. Figure 1 Example, both ends ( Figure 1 The leftmost and rightmost nodes adopt a 1+1 protection method (i.e., simultaneously passing through...). Figure 1 The solid line above is the main path and Figure 1 The following dotted-line backup path) is used for communication. The two-end nodes include multiple domains (metropolitan area, provincial trunk, and national trunk, each representing one domain). Each domain includes multiple sets of dual-homed nodes. Each set of dual-homed nodes includes one dual-homed primary node and one dual-homed backup node. Figure 1 In the central city domain (taking Wuhan as an example), the node in the upper right corner of the word "domain" is the dual-homed primary node, and the node in the lower right corner of the word "Han" is the dual-homed backup node; "inter-domain" refers to communication between a single domain and other domains, with each domain communicating through its own dual-homed primary node and dual-homed backup node.

[0003] However, the above method has the following drawbacks:

[0004] (1) If any fault occurs, both ends need to be switched, and the efficiency of troubleshooting is low.

[0005] (2) If one primary failure and one backup failure occur at the same time, the service may be interrupted and the reliability is low. Summary of the Invention

[0006] In view of the deficiencies in the existing technology, the technical problem solved by the present invention is: how to perform targeted replacement based on the faulty node and improve the troubleshooting efficiency.

[0007] To achieve the above objectives, this invention provides a small-granularity dual-homing protection switching method based on three-way APS code negotiation. This method is used in a primary / standby switching architecture, which includes multiple domains. Each domain includes several access nodes and several groups of dual-homing nodes. Each group of dual-homing nodes includes a dual-homing primary node and a dual-homing standby node. Each access node's primary path is to the dual-homing primary node, and its backup path is to the dual-homing standby node. Dual-homing primary nodes and dual-homing standby nodes within the same group communicate with each other. Dual-homing primary nodes in different groups communicate with each other, and dual-homing standby nodes communicate with each other. Each node's neighboring nodes are nodes in the same domain but different groups that it communicates with. The method includes the following steps:

[0008] Dual-homed primary and backup nodes within the same group communicate via DNI signaling messages, while dual-homed nodes communicate with nodes outside the same group via APS codes. Both DNI signaling messages and APS codes are used to inform the peer of the local path status and switching information. The DNI signaling message defines a dual-homed node type field and the following switching fields: intra-domain signal fault field, intra-domain switching field, inter-domain signal fault field, and inter-domain switching field. The APS code includes the working path signal failure field SF_W. When any node needs to perform a protection switch, it sends a DNI and / or APS code related to the reason for the protection switch to the corresponding node, and performs the protection switch based on the DNI and / or APS code.

[0009] Based on the above technical solutions, the intra-domain signal fault field is defined as iF, where 0 indicates normal and 1 indicates signal failure; the intra-domain switching field is defined as iS, where 0 indicates no switching and 1 indicates switching; the inter-domain signal fault field is defined as eF, where 0 indicates normal and 1 indicates signal failure; the inter-domain switching field is defined as eS, where 0 indicates no switching and 1 indicates switching; the dual-homing node type is defined as P, where 0 indicates dual-homing primary node and 1 indicates dual-homing backup node; NE2 represents a dual-homing primary node, NE3 represents a dual-homing backup node in the same group as NE2, and NE1 is the neighboring node of NE2 and NE3, with NE1 to NE3 forming one domain; NE4 represents a dual-homing primary node, NE5 represents a dual-homing backup node in the same group as NE2, and NE6 is the neighboring node of NE4 and NE5, with NE4 to NE6 forming one domain; NE2 and NE4, as well as NE3 and NE5, are all inter-domain nodes; messages sent from NE1 to NE6 are defined as eastbound traffic, and messages sent from NE6 to NE1 are defined as westbound traffic;

[0010] The protection failover rules for this method when all nodes are normal include:

[0011] Neighboring nodes forward service packets from dual-homed master nodes;

[0012] When a dual-homed primary node receives the same service message from a dual-homed backup node in the same group and a neighboring node, it forwards the service message sent by the neighboring node to another neighboring node; when a dual-homed primary node receives a service message sent by an inter-domain node, it sends it to the dual-homed backup node in the same group and a neighboring node, respectively.

[0013] When a dual-homed backup node receives a service message from a neighboring node, it forwards it to the dual-homed master node in the same group and another neighboring node, respectively. When a dual-homed backup node receives a service message from an inter-domain node and a dual-homed master node in the same group, it forwards the service message sent by the dual-homed master node to the neighboring node.

[0014] Dual-homed backup nodes communicate with neighboring nodes and inter-domain nodes via APS codes;

[0015] When all nodes are functioning normally, all information switching fields in the DNI signaling message are 0, and all APS codes are no-request fields.

[0016] Based on the above technical solution, when a failure occurs between the dual-homed primary node and its neighboring nodes, the dual-homed primary node at the point of failure is defined as the faulty primary node, and the dual-homed backup node in the same group as the faulty primary node is defined as the faulty backup node. After the faulty primary node detects the failure, it sends a DNI signaling message with iF=1 to the faulty backup node. After receiving the DNI signaling message with iS=1 from the dual-homed backup node, the faulty primary node performs service switching and forwards the service messages from the faulty backup node. After receiving the DNI signaling message with iF=1, the faulty backup node sends the primary SF_W APS code to its neighboring nodes. After receiving the APS code, the neighboring nodes perform service switching and forward the service messages from the faulty backup node.

[0017] After a neighboring node detects a fault, it sends the primary SF_W APS code to the faulty backup node. Upon receiving the APS code, the faulty backup node sends a DNI signaling message with iS=1 to the faulty primary node. Upon receiving the DNI signaling message, the faulty primary node performs service switching and forwards the service messages from the faulty backup node.

[0018] Based on the above technical solution, when a fault occurs between NE2 and NE4,

[0019] After NE2 detects a fault, it sends a DNI signaling message with eF=1 to NE3. After receiving the DNI signaling message with eS=1 from NE3, NE2 performs service switching and sends the service messages of the neighboring nodes to both NE4 and NE3.

[0020] After receiving the DNI signaling message with eF=1, NE3 sends the APS code of the primary SF_W and the service message from NE2 to NE5 respectively; NE5 receives the APS code of the primary SF_W and performs service switching, sending the service message from NE3 to NE4 and the neighboring node.

[0021] After NE4 detects a fault, it sends a DNI signaling message with eF=1 to NE5. After receiving the DNI signaling message with eS=1 from NE5, NE4 performs service switching and forwards the service messages from NE5 to the nearest node.

[0022] Based on the above technical solution, when there is a fault in the connection between NE1 and NE2, and between NE2 and NE4:

[0023] The workflow for eastbound traffic is as follows: NE2 sends a DNI signaling message with iF=1 and eF=1 to NE3; after receiving a DNI signaling message with iS=1, eS=1, and P=1 from NE3, NE2 performs a service switchover and forwards the service messages from NE3 to NE4; NE3 sends the primary SF_W APS code to NE1 and NE5 respectively, and forwards the service messages from NE1 to NE5; NE4 sends a DNI signaling message with eF=1 to NE5, and after receiving a DNI signaling message with eS=1 from NE5, NE4 performs a service switchover and forwards the service messages from NE5 to the nearest node;

[0024] The workflow for westbound traffic is as follows: NE4 sends a DNI signaling message with eF=1 to NE5. After receiving a DNI signaling message with eS=1 and P=1 from NE5, NE4 sends service messages to both NE5 and NE2. After receiving the DNI signaling message with eF=1 from NE4, NE5 replies with a DNI signaling message with eS=1 and P=1 and forwards the service messages from NE4 to NE3. NE3 then forwards the service messages from NE5 to both NE1 and NE2. NE1 sends the primary SF_W APS code to NE3 and forwards the service messages from NE3.

[0025] Based on the above technical solution, the APS code also includes the remote working path signal failure field SF_RW; when there is a fault from NE2 to NE3 or a fault from NE2 to NE4:

[0026] The workflow for eastbound traffic is as follows: NE1 sends service packets to both NE2 and NE3. NE3 selects service packets from NE1 and forwards them to NE5. After receiving the DNI signaling message with eF=1 from NE4, NE5 replies with a DNI signaling message with eS=1 and P=1. NE5 then sends the primary SF_W APS code to NE3 and forwards the service packets from NE3 to both NE4 and NE6. NE4 sends a DNI signaling message with eF=1 to NE5. After receiving the DNI signaling message with eS=1 and P=1 from NE5, NE4 selects the service packets from NE5 and forwards them to NE6. NE6 then forwards the service packets from NE4.

[0027] The workflow for westbound traffic is as follows: NE4 sends a DNI signaling message with eF=1 to NE5. After receiving a DNI signaling message with eS=1 and P=1 from NE5, NE4 sends service messages to both NE5 and NE2. After receiving the DNI signaling message with eF=1 from NE4, NE5 replies with a DNI signaling message with eS=1 and P=1. NE5 selects service messages from NE4 and sends them to NE3. NE3 then sends the service messages from NE5 to both NE1 and NE2. After receiving the primary SF_W APS from NE5 and the normal APS code from NE1, NE3 sends the SF_RW APS code to NE1. NE1 then forwards the service messages from NE3.

[0028] Based on the above technical solution, the APS code also includes a remote working path signal failure field SF_RW; when there is a fault between NE1 and NE2, or between NE2 and NE3:

[0029] In this scenario, the nodes requiring protection switching are NE1 to NE5. The specific process includes:

[0030] The workflow for eastbound traffic is as follows: NE3 transmits service packets from NE1 to both NE2 and NE5; after receiving the APS code of primary SF_W from NE1 and the normal APS code from NE5, NE3 sends the APS code of SF_RW to NE5; after receiving the APS code of SF_RW sent by NE3, NE5 transmits service packets from NE3 to both NE4 and NE6. NE5 sends a DNI signaling message with eS=1 and P=1 to NE4. NE4 then forwards the service packets from NE5 to NE6, and NE6 forwards the service packets from NE4.

[0031] The workflow for westbound traffic is as follows: After NE4 receives the DNI signaling message with eS=1 from NE5, it will send the service message from NE6 to both NE2 and NE5; After NE5 receives the APS code of SF_RW sent by NE3, it will select the service message from NE4 and send it to NE3; NE3 will send the service message from NE5 to NE1, and NE1 will forward the service message from NE3.

[0032] Based on the above technical solution, when the NE2 node loses power:

[0033] The workflow for eastbound traffic is as follows: NE3 selects service packets from NE1 and sends them to NE5; after receiving the DNI signaling message with eF=1 from NE4, NE5 replies with a DNI signaling message with eS=1 and P=1; NE5 sends the APS code of the inter-domain primary SF_W to NE3 and double-transmits the service packets from NE3 to NE4 and NE6; NE4 sends a DNI signaling message with eF=1 to NE5, and after receiving the DNI signaling message with eS=1 and P=1 from NE5, it selects the service packets from NE5 and forwards them to NE6; NE6 forwards the service packets from NE4.

[0034] The workflow for westbound traffic is as follows: NE4 sends a DNI signaling message with eF=1 to NE5. After receiving a DNI signaling message with eS=1 and P=1 from NE5, NE4 sends service messages to both NE5 and NE2. After receiving the DNI signaling message with eF=1 from NE4, NE5 replies with a DNI signaling message with eS=1 and P=1. NE5 selects service messages from NE4 and sends them to NE3. NE3 then sends service messages from NE5 to both NE1 and NE2. NE1 sends the primary SF_W APS code to NE3 and selects NE3 for service message forwarding.

[0035] The electronic device provided by the present invention includes a memory and a processor. The memory stores a computer program that runs on the processor, and the processor executes the computer program to implement the above-described method.

[0036] The small-granularity dual-homing protection switching system based on three-way APS code negotiation provided by the present invention includes a dual-homing master node and a dual-homing backup node, which are used to implement the above method.

[0037] Compared with the prior art, the advantages of the present invention are as follows:

[0038] Based on the characteristics of small-granularity services, this invention proposes the definition of relevant fields in the DNI message between dual-homing nodes. On this basis, it proposes a small-granularity dual-homing protection scheme based on three-way APS code negotiation. This scheme performs targeted switching according to the faulty node, which not only meets the protection requirements of small-granularity cross-domain services, but also eliminates the need for switching between both ends of any fault as required in the prior art, and improves troubleshooting efficiency.

[0039] Furthermore, based on the fault requirements of small particle protection scenarios, this invention expands the content of the existing standard APS code, solving some scenarios that are not supported by the RFC8185 PW dual-homing standard, and can ensure the operation of services when one primary fault and one backup fault occur simultaneously.

[0040] Therefore, this invention has made significant innovations in the protection and switching functions, and has the value of standardizing technical solutions. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 Deployment diagram for small-granularity cross-domain business instances in existing technologies;

[0043] Figure 2 This is a schematic diagram of the principle of scenario one in an embodiment of the present invention;

[0044] Figure 3 This is a schematic diagram of the principle of scenario two in an embodiment of the present invention;

[0045] Figure 4 This is a schematic diagram of the principle of scenario three in this embodiment of the invention;

[0046] Figure 5 This is a schematic diagram of the principle of scenario four in the embodiment of the present invention;

[0047] Figure 6 This is a schematic diagram of the principle of scenario five in this embodiment of the invention;

[0048] Figure 7 This is a schematic diagram of the principle of scenario six in the embodiment of the present invention;

[0049] Figure 8 This is a schematic diagram of the principle of scenario seven in an embodiment of the present invention. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0051] The flowchart shown in the attached diagram is for illustrative purposes only and does not necessarily include all content and operations / steps, nor does it necessarily have to be performed in the order described. For example, some operations / steps can be broken down, combined, or partially merged, so the actual execution order may change depending on the actual situation.

[0052] The research and development process of this invention will be introduced first.

[0053] To address the aforementioned issues, the Operator Research Institute, in conjunction with several equipment vendors (the applicant being one of them), conducted multiple rounds of intense discussions on small-granularity dual-homing cross-domain solutions. The parties reached a basic consensus, including:

[0054] (1) Use 1+1 double traffic between domains, and the business has the same path in both directions;

[0055] (2) Enable APS code negotiation between domains;

[0056] (3) DNI message negotiation is required between primary and backup dual-homed nodes;

[0057] In response to the above requirements, each equipment manufacturer has provided different implementation plans. Here, we will explain the specific plan developed by the applicant.

[0058] Based on this, the small-granularity dual-homing protection switching method based on three-way APS code negotiation in this embodiment of the invention includes the following steps:

[0059] A primary / backup failover architecture is established (this architecture already exists in practice, and subsequent solutions are based on it). This architecture includes multiple domains, each containing several access nodes and several groups of dual-homed nodes. Each group of dual-homed nodes includes a dual-homed primary node and a dual-homed backup node. The primary path for each access node is to the dual-homed primary node, and the backup path is to the dual-homed backup node. Dual-homed primary nodes and dual-homed backup nodes within the same group communicate with each other. Dual-homed primary nodes in different groups (including within and between domains) communicate with each other, and dual-homed backup nodes communicate with each other. Each node's neighboring nodes are defined as nodes in the same domain but different groups that communicate with it. The complete primary path is: an access node in one domain, several dual-homed primary nodes, and an access node in another domain. The backup path is: an access node in one domain, several dual-homed backup nodes, and an access node in another domain.

[0060] Dual-homed primary and dual-homed backup nodes within the same group also communicate via DNI (Dual-Node Interconnection) signaling messages. Dual-homed nodes and nodes outside the same group also communicate via APS (Automatic Protection Switching) codes. Both DNI signaling messages and APS codes are used to: inform the peer of the path status information and switching information of the local end; when any node needs to perform protection switching, it sends DNI and / or APS codes related to the reason for protection switching to the corresponding node, and performs protection switching according to DNI and / or APS codes.

[0061] It can be concluded that the "three directions" in the three-way APS code mentioned in this invention specifically refer to: the dual-homed master node and dual-homed backup node in the same group communicate through DNI signaling messages (1 direction), the dual-homed node communicates with neighboring nodes through APS codes (2 directions), and the dual-homed node communicates with inter-domain nodes through APS codes (3 directions).

[0062] Preferably, the method further includes the following steps: defining a dual-homed node type field and the following information switching fields in the DNI signaling message: intra-domain signal fault field, intra-domain signal degradation field, intra-domain switching field, inter-domain signal fault field, inter-domain signal degradation field, and inter-domain switching field, each switching information field including an identifier representing a normal type and an abnormal type.

[0063] Specifically, as shown in Table 1, this invention adds a DNI code block with Type = 0x3 after the APS code block with Type = 0x2 in the existing standard small-granularity service signaling code block. The DNI code block data content contains 4 data areas, named DNI_data[B0], DNI_data[B1], DNI_data[B2], and DNI_data[B3] in sequence.

[0064] Table 1. Type Architecture of DNI Signaling Messages Between Dual-homed Nodes

[0065]

[0066] Further details are shown in Table 2:

[0067] DNI_data[B0] stores domain information, using 3 bits of data, with the other bits reserved. Bit 2 is named Internal Domain Signal Fail (iF), where 0 indicates normal and 1 indicates signal failure (SF). Bit 1 is named Internal Domain Signal Degrade (iD), where 0 indicates normal and 1 indicates signal degrade (SD). Bit 0 indicates Internal Domain Switching (iS), where 0 indicates no switching and 1 indicates switching.

[0068] DNI_data[B1] stores inter-domain information, using 3 bits of data, with the other bits reserved. Bit 2 is named External Domain Signal Fail (eF), where 0 indicates normal and 1 indicates signal failure (SF). Bit 1 is named External Domain Signal Degrade (eD), where 0 indicates normal and 1 indicates signal degrade (SD). Bit 0 indicates External Domain Switching (eS), where 0 indicates no switching and 1 indicates switching.

[0069] DNI_data[B2] stores inter-domain information, using 1 bit of data and reserving the other bits. Bit0 indicates the dual-homed node type, abbreviated as P. 0 indicates a dual-homed master node (also known as a dual-homed working node), and 1 indicates a dual-homed backup node (also known as a dual-homed protection node). DNI_data[B3] is reserved.

[0070] Therefore, in the above text, 0 represents the normal type and 1 represents the abnormal type.

[0071] Table 2. Field representation of DNI signaling messages between dual-homed nodes

[0072]

[0073]

[0074] Meanwhile, as shown in Tables 3 and 4, under the definition of APS code format in the G.8331 standard, a new indication of remote working path failure (SF_RW) with a value of 1010 is added to the Request / state field of the APS code.

[0075] Table 3. Definition of G.8331 Standard APS Code Format

[0076]

[0077] Table 4. Request fields after APS code content expansion

[0078]

[0079]

[0080] See below. Figures 2-8As shown in any of the attached diagrams, NE1 to NE6 are used as nodes (solid lines represent primary paths, and dashed lines represent backup paths). The specific execution flow of the above method is explained in the following seven different scenarios. NE1 to NE3 are one domain, and NE4 to NE6 are another domain (for ease of description, the network diagram of the existing engineering network is simplified, and only three network devices are listed in each domain; however, the deployment of four or more devices in one domain is also within the scope of this patent). NE2 represents a dual-homed primary node, NE3 represents a dual-homed backup node in the same group as NE2, and NE1 is a neighboring node of NE2 and NE3. NE4 represents a dual-homed primary node, NE5 represents a dual-homed backup node in the same group as NE2, and NE6 is a neighboring node of NE4 and NE5. NE2 and NE4, as well as NE3 and NE5, are all inter-domain nodes. Packets sent from NE1 to NE6 are defined as eastbound traffic, and packets sent from NE6 to NE1 are defined as westbound traffic.

[0081] Scenario 1: Normal, fault-free scenario.

[0082] The small-granularity dual-homed primary / backup protection forwarding rule based on three-way APS code negotiation is as follows:

[0083] Neighboring nodes forward service packets from dual-homed master nodes;

[0084] When a dual-homed primary node receives the same service message from a dual-homed backup node in the same group and a neighboring node, it forwards the service message sent by the neighboring node to another neighboring node (referred to as intra-domain selective transmission); when a dual-homed primary node receives a service message sent by an inter-domain node, it sends it to the dual-homed backup node in the same group and a neighboring node respectively (referred to as inter-domain dual transmission).

[0085] When a dual-homed backup node receives a service message sent by a neighboring node, it sends it to the dual-homed master node in the same group and another neighboring node respectively (referred to as intra-domain dual transmission); when a dual-homed backup node receives a service message sent by an inter-domain node and a dual-homed master node in the same group respectively, it forwards the service message sent by the dual-homed master node to the neighboring node.

[0086] The dual backup node communicates with neighboring nodes and inter-domain nodes via APS codes.

[0087] See Figure 2 As shown, NE1 is configured with FGU1+1 dual-transmit and selectable same-source and different-destination protection based on G.8331. The source is the node itself, the primary path is to NE2, and the backup path is to NE3. NE2 and NE3 respectively deploy small-granularity dual-homing primary and backup protection models based on three-way APS code negotiation (i.e., the forwarding rules mentioned above); similarly, the same steps are taken for NE4 to NE6, which will not be repeated here.

[0088] See Figure 2As shown, the workflow for eastbound traffic (NE1 to NE6) is as follows: NE2 receives solid traffic (i.e., service messages) from NE1 and dashed traffic from NE3, and selects solid traffic to send to NE4; NE3 receives dashed traffic from NE1 and sends it to both NE2 and NE5; NE4 receives solid traffic from NE2 and sends it to both NE5 and NE6; NE5 receives dashed traffic from NE3 and solid traffic from NE4, and selects solid traffic to send to NE6.

[0089] See Figure 2 As shown, NE2 and NE3 send and receive DNI signaling messages to each other; NE3 sends and receives APS messages (i.e., APS codes) with neighboring nodes (i.e., intra-domain direction In) and with inter-domain nodes (i.e., inter-domain direction Ex); for ease of description, the APS code for intra-domain direction is defined as APS1, and the APS code for inter-domain direction is defined as APS2.

[0090] Based on this, taking NE3 as an example, as shown in Table 5, since the paths between NE3 and NE1, NE2, and NE5 are all normal in this scenario, therefore:

[0091] For DNI signaling messages: DNI receives a signaling message with all 7 bits set to 0, and DNI sends a message with P=1 (NE3 is a dual backup node). Therefore, P in the DNI messages sent by NE3 is always kept at 1.

[0092] For APS codes: APS1 and APS2 are both normal, meaning that both receiving and sending are normal (NR, No Request).

[0093] Table 5. Description of Three-Way Transmission and Reception of DNI Signaling Messages and APS Codes in Scenario 1

[0094]

[0095]

[0096] In Scenario 1, the westbound traffic (NE6 to NE1) follows the same logic as the eastbound traffic mentioned above, so it will not be repeated here.

[0097] Scenario 2: Single point of failure within the domain, i.e., a failure between the dual-homed master node and its neighboring nodes.

[0098] Here and below, the dual-homed primary node at the fault location is defined as the faulty primary node, and the dual-homed backup node in the same group as the faulty primary node is defined as the faulty backup node. After the faulty primary node detects the fault (the detection condition is that it has not received messages from neighboring nodes), it sends a DNI signaling message representing the signal fault field within the domain to the faulty backup node. After receiving the DNI signaling message representing the domain switchover from the dual-homed backup node, the faulty primary node performs service switchover, that is, forwards the service messages from the faulty backup node (or forwards the service messages from neighboring nodes under normal conditions). After receiving the DNI signaling message representing the signal fault field within the domain, the faulty backup node sends an APS code representing the primary path fault to neighboring nodes. After receiving the APS code, the neighboring nodes perform service switchover, that is, forward the service messages from the faulty backup node (or forward the service messages from the faulty primary node under normal conditions).

[0099] After a neighboring node detects a fault (the detection condition is that it has not received a message from the faulty primary node), it sends an APS code representing the primary path fault to the faulty backup node. After receiving the APS code, the faulty backup node sends a DNI signaling message representing intra-domain switching to the faulty primary node. After receiving the DNI signaling message, the faulty primary node performs service switching, that is, forwards the service messages from the faulty backup node.

[0100] See Figure 3 As shown, a path failure occurs between NE1 and NE2, triggering service failover only for NE1 and NE2. The workflow for eastbound traffic in this scenario is as follows:

[0101] NE1 transmits dual traffic, but only the dashed traffic goes to NE3. NE3 then transmits the dashed traffic from NE1 to both NE2 and NE5. NE2, due to a signal fault within its domain, sends a DNI signaling message with iF=1 to NE3. Upon receiving a DNI signaling message with iS=1 from NE3, NE2 performs a service switchover, selecting the dashed traffic to be sent to NE4. NE4 has no faults in any of its three directions, so no switchover is performed; it continues to transmit the dashed traffic from NE2 to both NE5 and NE6. NE5 also has no faults in any of its three directions, so no switchover is performed; it continues to select the dashed traffic from NE4 to be sent to NE6. NE6 then continues to prioritize the primary service, forwarding the traffic from NE4 eastward.

[0102] The westbound traffic flow process is as follows: NE6 transmits traffic twice, NE5 continues to transmit twice, NE4 selects solid line traffic from NE6 and sends it to NE2. NE2 then transmits solid line traffic from NE4 twice to NE1 (even though it is unreachable) and NE3. NE3 receives iF=1 from NE2, replies with iS=1, and sends the intra-domain primary fault APS code SF_W to NE1. It then continues to select solid line traffic from NE2 and forward it to NE1. Due to the primary fault, NE1 sends the primary fault APS code SF_W to NE3, switching back to receiving solid line traffic and continuing to forward it westward.

[0103] As shown in Table 6, the DNI signaling message and APS code for NE3 in this scenario are as follows:

[0104] Due to a path failure between NE1 and NE2, NE3 receives a DNI signaling message with iF=1 from NE2, indicating a signal failure within the master node domain. After processing by the dual-homing protection state machine, NE3 sends a DNI signaling message with iS=1 and P=1, indicating that services within the dual-homing master node NE2 domain can be switched over.

[0105] Both APS1 reception and transmission within the domain are due to primary path failure, with both reception and transmission being SF_W (Signal Fail on Working).

[0106] Inter-domain APS2 reception and transmission are both normal, and both reception and transmission are normal NR (No Request).

[0107] Table 6. Description of Three-Way Transmission and Reception of DNI Signaling Messages and APS Codes in Scenario 2

[0108]

[0109] Scenario 3: Single point of failure between domains, where the path between two dual-homed primary nodes between domains fails. The two dual-homed primary nodes are: the first failed primary node and the second failed primary node. Similarly, the nodes in the same group are: the first failed backup node and the second failed backup node.

[0110] After the first faulty master node detects the fault, it sends a DNI signaling message representing an inter-domain signaling fault to the first faulty backup node. After receiving the DNI signaling message representing inter-domain switching from the first faulty backup node, the first faulty master node performs service switching, that is, it double-transmits the service packets of the neighboring nodes to the second faulty master node and the first faulty backup node (normally the faulty master node selects and transmits within the domain, but now it only receives the service packets of the neighboring nodes and double-transmits them).

[0111] After receiving the DNI signaling message representing an inter-domain signaling failure, the first backup node sends an APS code representing a primary path failure (similarly, the second backup node will also send an APS code to the first backup node in the same way) and service packets from the first primary node (normally, it forwards service packets from neighboring nodes). Upon receiving the APS code representing a primary path failure, the second backup node performs service switching (similarly, the first backup node will also perform service switching upon receiving the APS code), which means it double-transmits service packets from the first backup node to both the second primary node and neighboring nodes (normally, the backup node uses selective inter-domain transmission, but now it only receives service packets from inter-domain nodes and double-transmits them).

[0112] After the second faulty master node detects the fault, it sends a DNI signaling message representing an inter-domain signaling fault to the second faulty backup node. After receiving the DNI signaling message representing inter-domain switching from the second faulty backup node, the second faulty master node performs service switching, that is, forwards the service messages from the second faulty backup node to the neighboring node (normally the faulty master node transmits to both inter-domain nodes, but now it only receives and forwards the service messages from the faulty backup node).

[0113] See Figure 4 As shown, a path fault occurs between NE2 and NE4. In this case, the protection switching is performed between NE2 and NE5, specifically as follows:

[0114] For eastbound traffic: NE1 transmits traffic in pairs. NE2 sends eF=1 to NE3 due to an inter-domain signal fault. After receiving the eS=1 message from NE3, it switches to transmitting the solid line traffic from NE1 in pairs to NE3 and NE4 (even though it is unreachable). After receiving the eF=1 from NE2, NE3 replies with eS=1. On the one hand, it sends the inter-domain primary fault APS code SF_W to NE5. On the other hand, it switches to sending the solid line traffic from NE2 to NE5.

[0115] NE4 sends eF=1 to NE5 due to an inter-domain signal fault. Upon receiving the message, NE5 replies with eS=1 and sends the inter-domain primary fault APS code SF_W to NE3. It then forwards the solid line traffic from NE3 to both NE4 and NE6. After receiving the eS=1 message from NE5, NE4 selects the solid line traffic from NE5 and forwards it to NE6. NE6, in turn, selects the solid line traffic from NE4 and forwards it eastward.

[0116] The logic for westbound and eastbound traffic is the same, so it will not be elaborated here.

[0117] As shown in Table 7, the DNI signaling message and APS code for NE3 in this scenario are as follows:

[0118] Due to a path failure between NE2 and NE4, NE3 receives a DNI signaling message eF=1 from NE2, indicating a signal failure between the master nodes. After processing by the dual-homing protection state machine, NE3 sends a DNI signaling message with eS=1 and P=1, indicating that the inter-domain services of the dual-homing master node NE2 can be switched over.

[0119] Within the domain, APS1 reception and transmission are both normal, and both reception and transmission are normal NR (No Request).

[0120] Both APS2 reception and transmission between domains are due to primary path failure, with both reception and transmission being SF_W (Signal Fail on Working).

[0121] Table 7. Description of Three-Way Transmission and Reception of DNI Signaling Messages and APS Codes in Scenario 3

[0122]

[0123] Scene 4, see Figure 5 As shown, the scenario involves multiple faults within and between domains, namely, a fault between NE1 and NE2 within the domain, and a fault between NE2 and NE4 between domains.

[0124] In this scenario, the nodes requiring protection switching are NE1 to NE5. The specific process includes:

[0125] The workflow for eastbound traffic (NE1 to NE6): NE1 sends traffic to both NE2 and NE3. Due to faults in both intra-domain and inter-domain communication, NE2 sends a DNI signaling message (iF=1, eF=1) to NE3 representing intra-domain and inter-domain signaling faults. After receiving a DNI signaling message (iS=1, eS=1, P=1) from NE3 representing intra-domain and inter-domain switching and switching type, NE2 performs a switching operation, forwarding service packets from NE3 to NE4. Simultaneously, NE3 also needs to send an APS code (SF_W) representing a primary path fault to both NE1 and NE5. NE3 then forwards the dotted-line traffic from NE1 to NE5. The subsequent process is the same as in Scenario 3.

[0126] NE4 sends eF=1 to NE5 due to an inter-domain signal fault. Upon receiving the message, NE5 replies with eS=1 and sends the inter-domain primary fault APS code SF_W to NE3. It then forwards the solid line traffic from NE3 to both NE4 and NE6. After receiving the eS=1 message from NE5, NE4 selects the solid line traffic from NE5 and forwards it to NE6. NE6, in turn, selects the solid line traffic from NE4 and forwards it eastward.

[0127] The workflow for westbound traffic (NE6 to NE1): NE6 transmits traffic to both NE4 and NE5. Due to an inter-domain signaling failure, NE4 sends a DNI signaling message (eF=1) to NE5 representing the inter-domain signaling failure. After receiving a DNI signaling message (eS=1, P=1) from NE5 representing inter-domain switching, NE4 switches to transmitting solid line traffic to both NE5 and NE2 (although unreachable). After receiving the DNI signaling message (eF=1) from NE4, NE5 replies with a DNI signaling message (eS=1, P=1) and then switches to transmitting solid line traffic from NE4 to NE3. NE3 then transmits solid line traffic from NE5 to both NE1 and NE2. Due to failures both within and between its domain, NE2 receives solid line traffic from NE3 and forwards it to NE1 (although unreachable). Due to a primary failure, NE1 sends a primary failure APS code (SF_W) to NE3 and simultaneously switches to receiving solid line traffic from NE3 for westward forwarding.

[0128] As shown in Table 8, the DNI signaling message and APS code for NE3 in this scenario are as follows:

[0129] If NE1 to NE2 and NE2 to NE4 within the domain both fail simultaneously, NE3 receives a DNI signaling message from NE2 with iF=1 and eF=1, indicating that both the intra-domain and inter-domain services of the master node are faulty. After processing by the dual-homing protection state machine, NE3 sends a DNI signaling message with iS=1, eS=1, and P=1, indicating that both intra-domain and inter-domain services of the dual-homing master node NE2 can be switched over.

[0130] Both APS1 reception and transmission within the domain are due to primary path failure, with both reception and transmission being SF_W (Signal Fail on Working).

[0131] Both APS2 reception and transmission between domains are due to primary path failure, with both reception and transmission being SF_W (Signal Fail on Working).

[0132] Table 8. Description of Three-Way Transmission and Reception of DNI Signaling Messages and APS Codes in Scenario 4

[0133]

[0134]

[0135] Scene 5, see Figure 6 As shown, the multi-point failure scenario within and between domains specifically includes: a failure between NE2 and NE3 within the domain, and a failure between NE2 and NE4 between domains. The existing PW dual-homing technology (RFC8185 standard) does not support this failure scenario; that is, prior to this application, eastbound services would be interrupted under this scenario.

[0136] In this scenario, the nodes requiring protection switching are NE1 to NE5. The specific process includes:

[0137] The workflow for eastbound traffic (NE1 to NE6): NE1 sends traffic twice. NE2 is unreachable eastward. Due to a DNI failure, NE3 switches to sending the dashed traffic from NE1 to NE5. After receiving the DNI signaling message (eF=1) from NE4, NE5 replies with a DNI signaling message of eS=1 and P=1, and simultaneously sends the Inter-Domain Primary Fault (APS) code SF_W to NE3. It then sends the dashed traffic from NE3 twice to both NE4 and NE6. Due to an inter-domain failure, NE4 sends a DNI signaling message (eF=1) to NE5. After receiving the reply DNI signaling message (eS=1 and P=1) from NE5, NE4 selects the dashed traffic from NE5 and forwards it to NE6. NE6 then again selects the dashed traffic from NE4 and forwards it eastward.

[0138] The workflow of westbound traffic (NE6 to NE1): NE6 sends traffic twice. Due to an inter-domain fault, NE4 sends a DNI signaling message eF=1 to NE5. NE5 replies with a DNI signaling message eS=1 and P=1. Then, it switches to sending solid line traffic to both NE5 and NE2 (although unreachable). After receiving the DNI signaling message eF=1 from NE4, NE5 replies with a DNI signaling message eS=1 and P=1. Then, it switches to sending solid line traffic from NE4 to NE3. NE3 forwards solid-line traffic from NE5 to both NE1 and NE2 (even though it is unreachable). Due to a DNI failure, and having received the primary inter-domain fault (SF_W) APS code from NE5 and the normal APS code from NE1, NE3 sends a remote primary path fault (SF_RW) to NE1. Upon receiving the APS code of the remote primary path fault (SF_RW) from NE3, NE1 knows that the remote path to the primary path of NE2 is unreachable, and therefore switches to the alternative path, i.e., forwarding the solid-line traffic from NE3 westward.

[0139] As shown in Table 9, the DNI signaling message and APS code for NE3 in this scenario are as follows:

[0140] If NE1 to NE3 within the domain and NE2 to NE4 between the domains all fail, the order of failure will cause differences in the DNI signaling messages received by NE3. If NE2 to NE4 between the domains fails first, NE3 can receive the DNI signaling message eF=1 sent by NE2. If NE1 to NE3 within the domain fails first, followed by NE2 to NE4 between the domains, NE2 will send a DNI signaling message eF=1, which NE3 cannot receive. Therefore, in this case, the DNI signaling message received by NE3 will be all 0s, consistent with normal operation. For the DNI signaling messages sent by NE3, since the DNI is already failed, the content of the sent messages is not restricted.

[0141] Within the domain, APS1 sends a newly defined remote primary path failure SF_RW (Signal Fail on RemoteWorking) and receives RR (Reverse Request).

[0142] Inter-domain APS2 reception is a primary path failure SF_W (Signal Fail on Working). Due to the differences in receiving DNI signaling mentioned earlier, the content sent by inter-domain APS2 also has two possibilities: If the inter-domain NE2 to NE4 fails first, NE3 can receive the DNI signaling message eF=1 sent by NE2, then the content sent by inter-domain APS2 is a primary path failure SF_W (Signal Fail on Working); if the intra-domain NE1 to NE3 fails first, the DNI signaling message in the receiving direction of NE3 is all 0s, then the content sent by inter-domain APS2 is a normal NR (No Request).

[0143] Table 9. Description of Three-Way Transmission and Reception of DNI Signaling Messages and APS Codes in Scenario 5

[0144]

[0145]

[0146] Scene Six, see also Figure 7 As shown, the multi-point failure scenario within the domain specifically refers to failures between NE1 and NE2, and between NE2 and NE3 within the domain. Existing PW dual-homing technology (RFC8185 standard) does not support this failure scenario; that is, prior to this application, westbound services would be interrupted under this scenario.

[0147] In this scenario, the nodes requiring protection switching are NE1 to NE5. The specific process includes:

[0148] Eastbound traffic: NE1 transmits traffic twice. NE3 transmits the dotted line traffic from NE1 twice to NE2 (although unreachable) and NE5. Due to a DNI failure, NE3 receives an APS code of primary failure SF_W from NE1 and a normal APS code NR from NE5, so it sends a remote primary path failure SF_RW (Signal Fail on Remote Working) to NE5. After receiving the APS code of SF_RW from NE3, NE5 switches to transmitting the dotted line traffic from NE3 twice to NE4 and NE6. At the same time, it sends a DNI signaling message to NE4 with eS=1 and P=1, triggering an inter-domain switchover for NE4. NE4 then forwards the dotted line traffic from NE5 to NE6, and NE6 still selects the dotted line traffic from NE4 for eastward forwarding.

[0149] Westbound traffic: NE6 transmits traffic twice. Because NE4 receives the DNI signaling message from NE5 with eS=1, it transmits the solid line traffic from NE6 to both NE2 and NE5. After receiving the SF_RW APS code sent by NE3, NE5 switches to send the solid line traffic from NE4 to NE3. NE3 sends the solid line traffic from NE5 to NE1. Due to the primary failure, NE1 switches to the backup path, i.e., forwarding the solid line traffic from NE3 westward.

[0150] As shown in Table 10, the DNI signaling message and APS code for NE3 in this scenario are as follows:

[0151] If both NE1 to NE2 and NE2 to NE3 within the domain fail, the order of failure will cause differences in the DNI signaling received by NE3. If NE1 to NE2 fails first, NE3 can receive the DNI signaling message iF=1 sent by NE5. If NE2 to NE3 fails first, followed by NE1 to NE2, NE2 will send a DNI signaling message iF=1, which NE3 cannot receive. Therefore, in this case, the DNI signaling message received by NE3 will be all 0s, consistent with normal operation. For the DNI signaling messages sent by NE3, since the DNI is already failed, the content is not restricted.

[0152] The APS1 reception within the domain is a primary path failure SF_W (Signal Fail on Working). Due to the differences in receiving DNI signaling mentioned earlier, the content sent by APS1 within the domain also has two possibilities: If the failure occurs first between NE1 and NE2 within the domain, then NE3 can receive the DNI signaling message iF=1 sent by NE2, and the content sent by APS1 within the domain is a primary path failure SF_W (Signal Fail on Working); if the failure occurs first between NE2 and NE3 within the domain, then the DNI signaling message in the receiving direction of NE3 is all 0s, and the content sent by APS1 within the domain is a normal NR (No Request).

[0153] Inter-domain APS2 sends a newly defined remote primary path failure SF_RW (Signal Fail on RemoteWorking) and receives RR (Reverse Request).

[0154] Table 10. Description of Three-Way Transmission and Reception of DNI Signaling Messages and APS Codes in Scenario 6

[0155]

[0156] Scene 7, see Figure 8 As shown, in the node power failure scenario, node NE2 loses power.

[0157] In this scenario, the nodes requiring protection switching are NE1, NE3, NE4, and NE5. The specific process includes:

[0158] Eastbound traffic: NE1 transmits traffic twice. Due to a DNI failure, NE3 switches to sending the dashed traffic from NE1 to NE5. After receiving the DNI signaling message eF=1 from NE4, NE5 replies with a DNI signaling message eS=1 and P=1. Simultaneously, NE5 sends the Inter-Domain Primary Fault (APS) code SF_W to NE3 and transmits the dashed traffic from NE3 twice to NE4 and NE6. NE4, due to an inter-domain failure, sends a DNI signaling message eF=1 to NE5. Upon receiving the reply from NE5 with a DNI signaling message eS=1 and P=1, NE4 then selects the dashed traffic from NE5 and forwards it to NE6. NE6, in turn, selects the dashed traffic from NE4 and forwards it eastward.

[0159] Westbound traffic: NE6 transmits traffic twice. NE4 sends a DNI signaling message eF=1 to NE5 due to an inter-domain fault. NE5 replies with a DNI signaling message eS=1 and P=1. NE5 then switches to transmitting solid line traffic twice to NE5 and NE2 (although unreachable). After receiving the DNI signaling message eF=1 from NE4, NE5 replies with a DNI signaling message eS=1 and P=1, and simultaneously switches to sending solid line traffic from NE4 to NE3. NE3 then transmits the solid line traffic from NE5 twice to NE1 and NE2 (although unreachable). NE1 sends a primary fault APS code SF_W to NE3 due to a primary fault, and switches to receiving solid line traffic to continue forwarding it westward.

[0160] As shown in Table 11, the DNI signaling message and APS code for NE3 in this scenario are as follows:

[0161] NE2 could be a centralized device or a distributed device;

[0162] For centralized equipment: If all three directions of NE2 fail simultaneously, the DNI signaling messages received by NE3 will be normal.

[0163] For distributed devices: Faults in the three directions may have millisecond-level time differences, which could result in the NE3 receiving a DNI signaling message that is normal, iF=1, or eF=1. Therefore, this is explained here. For the DNI signaling messages sent by the NE3, since the DNI has failed, the content of the sent messages is not limited.

[0164] The APS1 reception within the domain is a primary path failure SF_W (Signal Fail on Working). Due to the differences in receiving DNI signaling mentioned earlier, the content sent by APS1 within the domain also has two possibilities: If the failure occurs first between NE1 and NE2 within the domain, then NE3 can receive the DNI signaling message iF=1 sent by NE2, and the content sent by APS1 within the domain is a primary path failure SF_W (Signal Fail on Working); if the failure occurs first between NE2 and NE3 within the domain, then the DNI signaling message received by NE3 is all 0s, and the content sent by APS1 within the domain is a normal NR (No Request).

[0165] Inter-domain APS2 reception is a primary path failure SF_W (Signal Fail on Working). Due to the differences in receiving DNI signaling mentioned earlier, the content sent by inter-domain APS2 also has two possibilities: If the failure occurs first between NE2 and NE4, NE3 can receive the DNI signaling message eF=1 sent by NE2, then the content sent by inter-domain APS2 is a primary path failure SF_W (Signal Fail on Working); if the failure occurs first between NE1 and NE3 within the domain, the DNI signaling message received by NE3 will be all 0s, then the content sent by inter-domain APS2 is a normal NR (No Request).

[0166] Table 11. Description of Three-Way Transmission and Reception of DNI Signaling Messages and APS Codes in Scenario 7

[0167]

[0168] The electronic device in this embodiment of the invention is a communication board distributed on various nodes, specifically including a memory and a processor. The memory stores a computer program that runs on the processor, and the processor executes the computer program to implement the above method.

[0169] The small-granularity dual-homing protection switching system based on three-way APS code negotiation in this embodiment of the invention includes a dual-homing master node and a dual-homing backup node, which are used to implement the above method.

[0170] Those skilled in the art will understand that all or some of the steps, systems, and apparatuses disclosed above, and their functional modules / units, can be implemented as software, firmware, hardware, or suitable combinations thereof. In hardware implementations, the division between functional modules / units mentioned above does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed collaboratively by several physical components. Some or all physical components may be implemented as software executed by a processor, such as a central processing unit, digital signal processor, or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit (ASIC). Such software can be distributed on a computer-readable storage medium, which may include computer-readable storage media (or non-transitory media) and communication media (or transient media).

[0171] For example, the computer-readable storage medium may be an internal storage unit of the electronic device described in the foregoing embodiments, such as a hard disk or memory of the electronic device. The computer-readable storage medium may also be an external storage device of the electronic device, such as a plug-in hard disk, smart media card (SMC), secure digital card (SD), flash card, etc., provided on the electronic device.

[0172] The above are merely specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the scope of the claims.

Claims

1. A small-granularity dual-homing protection switching method based on three-way APS code negotiation, used in a primary / backup switching architecture, which includes multiple domains, each domain including several access nodes and several groups of dual-homing nodes, each group of dual-homing nodes including a dual-homing primary node and a dual-homing backup node; each access node's primary path is to the dual-homing primary node, and its backup path is to the dual-homing backup node; dual-homing primary nodes and dual-homing backup nodes within the same group communicate with each other; dual-homing primary nodes in different groups communicate with each other, and dual-homing backup nodes communicate with each other; the neighboring nodes of each node are nodes in the same domain but different groups that communicate with it; characterized in that, The method includes the following steps: Dual-homed primary and backup nodes within the same group communicate via DNI signaling messages, while dual-homed nodes communicate with nodes outside the same group via APS codes. Both DNI signaling messages and APS codes are used to inform the peer of the local path status and switching information. The DNI signaling message defines a dual-homed node type field and the following switching fields: intra-domain signal fault field, intra-domain switching field, inter-domain signal fault field, and inter-domain switching field. The APS code includes the working path signal failure field SF_W. When any node needs to perform a protection switch, it sends a DNI and / or APS code related to the reason for the protection switch to the corresponding node, and performs the protection switch based on the DNI and / or APS code.

2. The small-granularity dual-homing protection switching method based on three-way APS code negotiation as described in claim 1, characterized in that: The intra-domain signal fault field is defined as iF, where 0 indicates normal and 1 indicates signal failure; the intra-domain switching field is defined as iS, where 0 indicates no switching and 1 indicates switching; the inter-domain signal fault field is defined as eF, where 0 indicates normal and 1 indicates signal failure; the inter-domain switching field is defined as eS, where 0 indicates no switching and 1 indicates switching; the dual-homing node type is defined as P, where 0 indicates dual-homing primary node and 1 indicates dual-homing backup node; NE2 represents a dual-homing primary node, NE3 represents a dual-homing backup node in the same group as NE2, NE1 is the neighboring node of NE2 and NE3, and NE1 to NE3 constitute one domain; Define NE4 as the dual-homed primary node, NE5 as the dual-homed backup node in the same group as NE2, and NE6 as the neighboring node of NE4 and NE5. NE4 to NE6 constitute one domain. NE2 and NE4, as well as NE3 and NE5, are all inter-domain nodes; Messages sent from NE1 to NE6 are defined as eastbound traffic, and messages sent from NE6 to NE1 are defined as westbound traffic. The protection failover rules for this method when all nodes are normal include: Neighboring nodes forward service packets from dual-homed master nodes; When a dual-homed primary node receives the same service message from a dual-homed backup node in the same group and a neighboring node, it forwards the service message sent by the neighboring node to another neighboring node; when a dual-homed primary node receives a service message sent by an inter-domain node, it sends it to the dual-homed backup node in the same group and a neighboring node, respectively. When a dual-homed backup node receives a service message from a neighboring node, it forwards it to the dual-homed master node in the same group and another neighboring node, respectively. When a dual-homed backup node receives a service message from an inter-domain node and a dual-homed master node in the same group, it forwards the service message sent by the dual-homed master node to the neighboring node. Dual-homed backup nodes communicate with neighboring nodes and inter-domain nodes via APS codes; When all nodes are functioning normally, all information switching fields in the DNI signaling message are 0, and all APS codes are no-request fields.

3. The small-granularity dual-homing protection switching method based on three-way APS code negotiation as described in claim 2, characterized in that: When a failure occurs between a dual-homed primary node and its neighboring nodes, the dual-homed primary node at the point of failure is defined as the faulty primary node, and the dual-homed backup node in the same group as the faulty primary node is defined as the faulty backup node. After the faulty primary node detects the failure, it sends a DNI signaling message with iF=1 to the faulty backup node. After receiving the DNI signaling message with iS=1 from the dual-homed backup node, the faulty primary node performs service switching and forwards service messages from the faulty backup node. After receiving the DNI signaling message with iF=1, the faulty backup node sends an APS code of primary SF_W to its neighboring nodes. After receiving the APS code, the neighboring nodes perform service switching and forward service messages from the faulty backup node. After a neighboring node detects a fault, it sends the primary SF_W APS code to the faulty backup node. Upon receiving the APS code, the faulty backup node sends a DNI signaling message with iS=1 to the faulty primary node. Upon receiving the DNI signaling message, the faulty primary node performs service switching and forwards the service messages from the faulty backup node.

4. The small-granularity dual-homing protection switching method based on three-way APS code negotiation as described in claim 2, characterized in that: When a fault occurs between NE2 and NE4 After NE2 detects a fault, it sends a DNI signaling message with eF=1 to NE3. After receiving the DNI signaling message with eS=1 from NE3, NE2 performs service switching and sends the service messages of the neighboring nodes to both NE4 and NE3. After receiving the DNI signaling message with eF=1, NE3 sends the APS code of the primary SF_W and the service message from NE2 to NE5 respectively; NE5 receives the APS code of the primary SF_W and performs service switching, sending the service message from NE3 to NE4 and the neighboring node. After NE4 detects a fault, it sends a DNI signaling message with eF=1 to NE5. After receiving the DNI signaling message with eS=1 from NE5, NE4 performs service switching and forwards the service messages from NE5 to the nearest node.

5. The small-granularity dual-homing protection switching method based on three-way APS code negotiation as described in claim 2, characterized in that: When there is a fault between NE1 and NE2, and between NE2 and NE4: The workflow for eastbound traffic is as follows: NE2 sends a DNI signaling message with iF=1 and eF=1 to NE3; after receiving a DNI signaling message with iS=1, eS=1, and P=1 from NE3, NE2 performs a service switchover and forwards the service messages from NE3 to NE4; NE3 sends the primary SF_W APS code to NE1 and NE5 respectively, and forwards the service messages from NE1 to NE5; NE4 sends a DNI signaling message with eF=1 to NE5, and after receiving a DNI signaling message with eS=1 from NE5, NE4 performs a service switchover and forwards the service messages from NE5 to the nearest node; The workflow for westbound traffic is as follows: NE4 sends a DNI signaling message with eF=1 to NE5. After receiving a DNI signaling message with eS=1 and P=1 from NE5, NE4 sends service messages to both NE5 and NE2. After receiving the DNI signaling message with eF=1 from NE4, NE5 replies with a DNI signaling message with eS=1 and P=1 and forwards the service messages from NE4 to NE3. NE3 then forwards the service messages from NE5 to both NE1 and NE2. NE1 sends the primary SF_W APS code to NE3 and forwards the service messages from NE3.

6. The small-granularity dual-homing protection switching method based on three-way APS code negotiation as described in claim 2, characterized in that: The APS code also includes the remote working path signal failure field SF_RW; when there is a fault between NE2 and NE3, or a fault between NE2 and NE4: The workflow for eastbound traffic is as follows: NE1 sends service packets to both NE2 and NE3. NE3 selects service packets from NE1 and forwards them to NE5. After receiving the DNI signaling message with eF=1 from NE4, NE5 replies with a DNI signaling message with eS=1 and P=1. NE5 then sends the primary SF_W APS code to NE3 and forwards the service packets from NE3 to both NE4 and NE6. NE4 sends a DNI signaling message with eF=1 to NE5. After receiving the DNI signaling message with eS=1 and P=1 from NE5, NE4 selects the service packets from NE5 and forwards them to NE6. NE6 then forwards the service packets from NE4. The workflow for westbound traffic is as follows: NE4 sends a DNI signaling message with eF=1 to NE5. After receiving a DNI signaling message with eS=1 and P=1 from NE5, NE4 sends service messages to both NE5 and NE2. After receiving the DNI signaling message with eF=1 from NE4, NE5 replies with a DNI signaling message with eS=1 and P=1, and selects the service messages from NE4 to send to NE3. NE3 then sends the service messages from NE5 to both NE1 and NE2. After receiving the primary SF_W APS from NE5 and the normal APS code from NE1, NE3 sends the SF_RW APS code to NE1. NE1 forwards the service messages from NE3.

7. The small-granularity dual-homing protection switching method based on three-way APS code negotiation as described in claim 2, characterized in that: The APS code also includes the remote working path signal failure field SF_RW; when there is a fault between NE1 and NE2, or between NE2 and NE3: In this scenario, the nodes requiring protection switching are NE1 to NE5. The specific process includes: The workflow for eastbound traffic is as follows: NE3 transmits service packets from NE1 to both NE2 and NE5; after receiving the APS code of primary SF_W from NE1 and the normal APS code from NE5, NE3 sends the APS code of SF_RW to NE5; after receiving the APS code of SF_RW sent by NE3, NE5 transmits service packets from NE3 to both NE4 and NE6. NE5 sends a DNI signaling message with eS=1 and P=1 to NE4. NE4 then forwards the service packets from NE5 to NE6, and NE6 forwards the service packets from NE4. The workflow for westbound traffic is as follows: After NE4 receives the DNI signaling message with eS=1 from NE5, it will send the service message from NE6 to both NE2 and NE5; After NE5 receives the APS code of SF_RW sent by NE3, it will select the service message from NE4 and send it to NE3; NE3 will send the service message from NE5 to NE1, and NE1 will forward the service message from NE3.

8. The small-granularity dual-homing protection switching method based on three-way APS code negotiation as described in claim 2, characterized in that: When NE2 node loses power: The workflow for eastbound traffic is as follows: NE3 selects service packets from NE1 and sends them to NE5; after receiving the DNI signaling message with eF=1 from NE4, NE5 replies with a DNI signaling message with eS=1 and P=1; NE5 sends the APS code of the inter-domain primary SF_W to NE3 and double-transmits the service packets from NE3 to NE4 and NE6; NE4 sends a DNI signaling message with eF=1 to NE5, and after receiving the DNI signaling message with eS=1 and P=1 from NE5, it selects the service packets from NE5 and forwards them to NE6; NE6 forwards the service packets from NE4. The workflow for westbound traffic is as follows: NE4 sends a DNI signaling message with eF=1 to NE5. After receiving a DNI signaling message with eS=1 and P=1 from NE5, NE4 sends service messages to both NE5 and NE2. After receiving the DNI signaling message with eF=1 from NE4, NE5 replies with a DNI signaling message with eS=1 and P=1. NE5 selects service messages from NE4 and sends them to NE3. NE3 then sends service messages from NE5 to both NE1 and NE2. NE1 sends the primary SF_W APS code to NE3 and selects NE3 for service message forwarding.

9. An electronic device comprising a memory and a processor, wherein the memory stores a computer program that runs on the processor, characterized in that: The processor executes a computer program to implement the method described in any one of claims 1 to 8.

10. A small-granularity dual-homing protection switching system based on three-way APS code negotiation, characterized in that: The system includes a dual-homing master node and a dual-homing backup node, which are used to implement the method described in any one of claims 1 to 8.

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